Plants&Bacteria
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Plants&Bacteria
A selection of publications concerning the diverse relationship between plants and microorganisms, with some special atention to plant-pathogenic bacteria.
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HrcT is a key component of the type III secretion system in Xanthomonas and also regulates the expression of the key hrp transcriptional activator HrpX

HrcT is a key component of the type III secretion system in Xanthomonas and also regulates the expression of the key hrp transcriptional activator HrpX | Plants&Bacteria | Scoop.it

Scooped from: Applied and Environmental Microbiology, 2014

Authors: Zhi-Yang Liu, Li-Fang Zou, Xiao-Bo Xue, Lu-Lu Cai, Wen-Xiu Ma, Li Xiong, Zhi-Yuan Ji and Gong-You Chen.

 

Summary:

The type III secretion system (T3SS), encoded by hrp (hypersensitive response and pathogenicity) genes in Gram-negative phytopathogenic bacteria, delivers repertoires of T3SS effectors (T3SEs) into plant cells to trigger the hypersensitive response (HR) in nonhost or resistant host plants and promote pathogenicity in susceptible plants. The expression of hrp genes in Xanthomonas is regulated by two key regulatory proteins, HrpG and HrpX. However, the interactions between hrp gene products in directing T3SE secretion are largely unknown. Here we demonstrated that HrcT of X. oryzae pv. oryzicola (Xoc) functions as a T3SS component and positively regulates the expression of hrpX. Transcription of hrcT occurs via two distinct promoters, one is with the hrpB operon (T1) and the second (T3) within hrpB7. Via either T1 or T3 promoter, the defect in Hrp phenotype by hrcT deletion was restored in the presence of hrcT only from Xanthomonas species, but not other phytopathogenic bacteria. An N-terminally truncated HrcT was able to bind the hrpX promoter and activate the expression of hrpX, supporting that HrcT is a positive regulator of hrpX. A revised model showing the regulatory interactions between HrcT, HrpX and HrpG is proposed.

Freddy Monteiro's insight:

Glad to know I was following the right path... it was a question of time before seeing this fine-tuning mechanisms described in plant pathogenic bacteria. This is a MUST reference for genetic studies of pathogenicity.

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Rescooped by Freddy Monteiro from Effectors and Plant Immunity
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PLoS ONE: Real Time Live Imaging of Phytopathogenic Bacteria Xanthomonas campestris pv. campestris MAFF106712 in ‘Plant Sweet Home’ (2014)

PLoS ONE: Real Time Live Imaging of Phytopathogenic Bacteria Xanthomonas campestris pv. campestris MAFF106712 in ‘Plant Sweet Home’ (2014) | Plants&Bacteria | Scoop.it

Xanthomonas is one of the most widespread phytobacteria, causing diseases on a variety of agricultural plants. To develop novel control techniques, knowledge of bacterial behavior inside plant cells is essential. Xanthomonas campestris pv. campestris, a vascular pathogen, is the causal agent of black rot on leaves of Brassicaceae, including Arabidopsis thaliana. Among the X. campestris pv. campestris stocks in the MAFF collection, we selected XccMAFF106712 as a model compatible pathogen for the A. thaliana reference ecotype Columbia (Col-0). Using modified green fluorescent protein (AcGFP) as a reporter, we observed real time XccMAFF106712 colonization in planta with confocal microscopy. AcGFP-expressing bacteria colonized the inside of epidermal cells and the apoplast, as well as the xylem vessels of the vasculature. In the case of the type III mutant, bacteria colonization was never detected in the xylem vessel or apoplast, though they freely enter the xylem vessel through the wound. After 9 days post inoculation with XccMAFF106712, the xylem vessel became filled with bacterial aggregates. This suggests that Xcc colonization can be divided into main four steps, (1) movement in the xylem vessel, (2) movement to the next cell, (3) adhesion to the host plant cells, and (4) formation of bacterial aggregates. The type III mutant abolished at least steps (1) and (2). Better understanding of Xcc colonization is essential for development of novel control techniques for black rot.

 

Chiharu Akimoto-Tomiyama,  Ayako Furutani,  Hirokazu Ochiai

 


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Freddy Monteiro's comment, April 17, 9:21 AM
"Real-time imaging of showing release of bacteria from the xylem vessel is shown in Movies S8, S9. The bacteria seemed to be aggregated inside the xylem vessel 9 days post inoculation (Figures 7B, S2, Movie S9), with the size of the aggregates depending on each xylem vessel. Notably, the size of the aggregates within a single xylem vessel was relatively consistent. In contrast, bacteria from a xylem vessel only 6 days post inoculation (Figure 7A, Movie S8) seemed not to make such bacterial aggregates, but rather to remain as single cells. The size of bacterial aggregates was measured as pixels of the area showing AcGFP fluorescence, demonstrating the size of the aggregates dramatically increases between 6 and 9 days (Figure 7C). We also noted that the released bacterial aggregates did not move, while single bacteria moved vigorously (Movie S10). At 6 days post inoculation, the infected site in the xylem vessel appeared transversely extended (Movie S4) and most of the bacteria did not move (Movie S3). From these observations, we conclude that active single bacteria with high motility move freely inside the xylem vessel, and upon finding a suitable niche (such as one with a low abundance of other bacteria), they adhere to the plant cells and starts multiplying"
Freddy Monteiro's comment, April 17, 9:24 AM
I find that excerpt very interesting. A similar discussion was held in my PhD defense regarding R.solanacearum infection. This is a nice piece of work =)
Suayib Üstün's comment, April 18, 8:17 AM
interesting, however citation 46 is wrong. should be üstün et al., 2013. ;-)
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Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria

Commonalities and differences of T3SSs in rhizobia and plant pathogenic bacteria | Plants&Bacteria | Scoop.it

Scooped from: Front Plant Sci., 2014

Author: Anastasia P. Tampakaki

 

Summary:

Plant pathogenic bacteria and rhizobia infect higher plants albeit the interactions with their hosts are principally distinct and lead to completely different phenotypic outcomes, either pathogenic or mutualistic, respectively. Bacterial protein delivery to plant host plays an essential role in determining the phenotypic outcome of plant-bacteria interactions. The involvement of type III secretion systems (T3SSs) in mediating animal- and plant-pathogen interactions was discovered in the mid-80’s and is now recognized as a multiprotein nanomachine dedicated to trans-kingdom movement of effector proteins. The discovery of T3SS in bacteria with symbiotic lifestyles broadened its role beyond virulence. In most T3SS-positive bacterial pathogens, virulence is largely dependent on functional T3SSs, while in rhizobia the system is dispensable for nodulation and can affect positively or negatively the mutualistic associations with their hosts. This review focuses on recent comparative genome analyses in plant pathogens and rhizobia that uncovered similarities and variations among T3SSs in their genetic organization, regulatory networks and type III secreted proteins and discusses the evolutionary adaptations of T3SSs and type III secreted proteins that might account for the distinguishable phenotypes and host range characteristics of plant pathogens and symbionts.

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Rescooped by Freddy Monteiro from Plant-microbe interaction
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HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants

HopZ4 from Pseudomonas syringae, a member of the HopZ type III effector family from the YopJ superfamily, inhibits the proteasome in plants | Plants&Bacteria | Scoop.it

The YopJ-family of type III effector (T3E) proteins is one of the largest and widely distributed families of effector proteins whose members are highly diversified in virulence functions. In the present study, HopZ4, a member of the YopJ-family of T3Es from the cucumber pathogen Pseudomonas syringae pv. lachrymans is described. HopZ4 shares high sequence similarity with the Xanthomonas T3E XopJ and a functional analysis suggests a conserved virulence function between these two T3Es. As has previously shown for XopJ, HopZ4 interacts with the proteasomal subunit RPT6 in yeast and in planta to inhibit proteasome activity during infection. The inhibitory effect on the proteasome is dependent on localization of HopZ4 to the plasma membrane as well as on an intact catalytic triad of the effector protein. Furthermore, HopZ4 is able to complement loss of XopJ in Xanthomonas as it prevents precocious host cell death during a compatible interaction of Xanthomonas with pepper. The data presented here suggest that different bacterial species employ inhibition of the proteasome as a virulence strategy by making use of conserved T3Es from the YopJ-family of bacterial effector proteins.


Via Suayib Üstün
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Rescooped by Freddy Monteiro from microbial pathogenesis and plant immunity
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Tyrosine phosphorylation of protein kinase complex BAK1/BIK1 mediates Arabidopsis innate immunity

Tyrosine phosphorylation of protein kinase complex BAK1/BIK1 mediates Arabidopsis innate immunity | Plants&Bacteria | Scoop.it

Scooped from: PNAS, 2014 (/via Jim Alfano and Suayib üstün)

Authors: Wenwei Lin, Bo Li, Dongping Lu, Sixue Chen, Ning Zhu, Ping He, and Libo Shan

 

Abstract:

The sessile plants have evolved a large number of receptor-like kinases (RLKs) and receptor-like cytoplasmic kinases (RLCKs) to modulate diverse biological processes, including plant innate immunity. Phosphorylation of the RLK/RLCK complex constitutes an essential step to initiate immune signaling. Two Arabidopsis plasma membrane-resident RLKs, flagellin-sensing 2 and brassinosteroid insensitive 1-associated kinase 1 (BAK1), interact with RLCK Botrytis-induced kinase 1 (BIK1) to initiate plant immune responses to bacterial flagellin. BAK1 directly phosphorylates BIK1 and positively regulates plant immunity. Classically defined as a serine/threonine kinase, BIK1 is shown here to possess tyrosine kinase activity with mass spectrometry, immunoblot, and genetic analyses. BIK1 is autophosphorylated at multiple tyrosine (Y) residues in addition to serine/threonine residues. Importantly, BAK1 is able to phosphorylate BIK1 at both tyrosine and serine/threonine residues. BIK1Y150 is likely catalytically important as the mutation blocks both tyrosine and serine/threonine kinase activity, whereas Y243 and Y250 are more specifically involved in tyrosine phosphorylation. The BIK1 tyrosine phosphorylation plays a crucial role in BIK1-mediated plant innate immunity as the transgenic plants carrying BIK1Y150F, Y243F, or Y250F (the mutation of tyrosine to phenylalanine) failed to complement the bik1 mutant deficiency in immunity. Our data indicate that plant RLCK BIK1 is a nonreceptor dual-specificity kinase and both tyrosine and serine/threonine kinase activities are required for its functions in plant immune signaling. Together with the previous finding of BAK1 to be autophosphorylated at tyrosine residues, our results unveiled the tyrosine phosphorylation cascade as a common regulatory mechanism that controls membrane-resident receptor signaling in plants and metazoans.


Via Suayib Üstün, Jim Alfano
Freddy Monteiro's insight:

Tyr phosphorilation in plant immunity:

BAK1/BIK1 complex

 http://www.pnas.org/cgi/content/long/1318817111v1

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Jim Alfano's curator insight, February 18, 3:07 PM

Does the P. syringae HopAO1 tyrosine phosphatase effector act on BIK1?

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Targeted Mutagenesis in Zea mays Using TALENs and the CRISPR/Cas System

Targeted Mutagenesis in Zea mays Using TALENs and the CRISPR/Cas System | Plants&Bacteria | Scoop.it

Scooped from: Journal of Genetics and Genomics, 2014 (/via @dromius)

Title: Targeted Mutagenesis in Zea mays Using TALENs and the CRISPR/Cas System

Authors: Zhen Liang, Kang Zhang, Kunling Chen and Caixia Gao.

 

Abtract:

Transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) systems have emerged as powerful tools for genome editing in a variety of species. Here, we report, for the first time, targeted mutagenesis in Zea mays using TALENs and the CRISPR/Cas system. We designed five TALENs targeting 4 genes, namely ZmPDS, ZmIPK1A, ZmIPK, ZmMRP4, and obtained targeting efficiencies of up to 23.1% in protoplasts, and about 13.3% to 39.1% of the transgenic plants were somatic mutations. Also, we constructed two gRNAs targeting the ZmIPK gene in maize protoplasts, at frequencies of 16.4% and 19.1%, respectively. In addition, the CRISPR/Cas system induced targeted mutations in Z. mays protoplasts with efficiencies (13.1%) similar to those obtained with TALENs (9.1%). Our results show that both TALENs and the CRISPR/Cas system can be used for genome modification in maize.


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Ilyas Muhammad's comment, December 17, 2013 6:19 AM
thnx, Seb
Rescooped by Freddy Monteiro from Plant Immunity And Microbial Effectors
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The small phytoplasma virulence effector SAP11 contains distinct domains required for nuclear targeting and CIN-TCP binding and destabilization

The small phytoplasma virulence effector SAP11 contains distinct domains required for nuclear targeting and CIN-TCP binding and destabilization | Plants&Bacteria | Scoop.it

/via IPMLab scoop.it

Scooped from: The New Phytologist, 2014

Authors: Akiko Sugio, Allyson M. MacLean andSaskia A. Hogenhout

 

Abstract:

Phytoplasmas are insect-transmitted bacterial phytopathogens that secrete virulence effectors and induce changes in the architecture and defense response of their plant hosts. We previously demonstrated that the small (± 10 kDa) virulence effector SAP11 of Aster Yellows phytoplasma strain Witches' Broom (AY-WB) binds and destabilizes Arabidopsis CIN (CINCINNATA) TCP (TEOSINTE-BRANCHED, CYCLOIDEA, PROLIFERATION FACTOR 1 AND 2) transcription factors, resulting in dramatic changes in leaf morphogenesis and increased susceptibility to phytoplasma insect vectors. SAP11 contains a bipartite nuclear localization signal (NLS) that targets this effector to plant cell nuclei.To further understand how SAP11 functions, we assessed the involvement of SAP11 regions in TCP binding and destabilization using a series of mutants.SAP11 mutants lacking the entire N-terminal domain, including the NLS, interacted with TCPs but did not destabilize them. SAP11 mutants lacking the C-terminal domain were impaired in both binding and destabilization of TCPs. These SAP11 mutants did not alter leaf morphogenesis. A SAP11 mutant that did not accumulate in plant nuclei (SAP11ΔNLS-NES) was able to bind and destabilize TCP transcription factors, but instigated weaker changes in leaf morphogenesis than wild-type SAP11.Overall the results suggest that phytoplasma effector SAP11 has a modular organization in which at least three domains are required for efficient CIN-TCP destabilization in plants.


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The bHLH Transcription Factor HBI1 Mediates the Trade-Off between Growth and Pathogen-Associated Molecular Pattern–Triggered Immunity in Arabidopsis

The bHLH Transcription Factor HBI1 Mediates the Trade-Off between Growth and Pathogen-Associated Molecular Pattern–Triggered Immunity in Arabidopsis | Plants&Bacteria | Scoop.it

The trade-off between growth and immunity is crucial for survival in plants. However, the mechanism underlying growth-immunity balance has remained elusive. The PRE-IBH1-HBI1 tripartite helix-loop-helix/basic helix-loop-helix module is part of a central transcription network that mediates growth regulation by several hormonal and environmental signals. Here, genome-wide analyses of HBI1 target genes show that HBI1 regulates both overlapping and unique targets compared with other DNA binding components of the network in Arabidopsis thaliana, supporting a role in specifying network outputs and fine-tuning feedback regulation. Furthermore, HBI1 negatively regulates a subset of genes involved in immunity, and pathogen-associated molecular pattern (PAMP) signals repress HBI1 transcription. Constitutive overexpression and loss-of-function experiments show that HBI1 inhibits PAMP-induced growth arrest, defense gene expression, reactive oxygen species production, and resistance to pathogen. These results show that HBI1, as a component of the central growth regulation circuit, functions as a major node of crosstalk that mediates a trade-off between growth and immunity in plants.


Via Suayib Üstün, Christophe Jacquet
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Breaking dogmas: the plant vascular pathogen Xanthomonas albilineans is able to invade non-vascular tissues despite its reduced genome

Breaking dogmas: the plant vascular pathogen Xanthomonas albilineans is able to invade non-vascular tissues despite its reduced genome | Plants&Bacteria | Scoop.it

Scooped from: Open Biology, 2014

Authors: Imène Mensi, Marie-Stéphanie Vernerey, Daniel Gargani, Michel Nicole and Philippe Rott

 

Abstract:

Xanthomonas albilineans, the causal agent of sugarcane leaf scald, is missing the Hrp type III secretion system that is used by many Gram-negative bacteria to colonize their host. Until now, this pathogen was considered as strictly limited to the xylem of sugarcane. We used confocal laser scanning microscopy, immunocytochemistry and transmission electron microscopy (TEM) to investigate the localization of X. albilineans in diseased sugarcane. Sugarcane plants were inoculated with strains of the pathogen labelled with a green fluorescent protein. Confocal microscopy observations of symptomatic leaves confirmed the presence of the pathogen in the protoxylem and metaxylem; however, X. albilineans was also observed in phloem, parenchyma and bulliform cells of the infected leaves. Similarly, vascular bundles of infected sugarcane stalks were invaded by X. albilineans. Surprisingly, the pathogen was also observed in apparently intact storage cells of the stalk and in intercellular spaces between these cells. Most of these observations made by confocal microscopy were confirmed by TEM. The pathogen exits the xylem following cell wall and middle lamellae degradation, thus creating openings to reach parenchyma cells. This is the first description of a plant pathogenic vascular bacterium invading apparently intact non-vascular plant tissues and multiplying in parenchyma cells.

Freddy Monteiro's insight:

I was not aware of this journal until now. However the microscopy images in this publication are neat.
Great to see good'ol school transmission electron microscopy images complemented with confocal observations.  

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Establishment of an inducing medium for type III effector secretion in Xanthomonas campestris pv. campestris.

Establishment of an inducing medium for type III effector secretion in Xanthomonas campestris pv. campestris. | Plants&Bacteria | Scoop.it

Scooped from: Braz. J. Microbiol., 2013

Authors: Guo-Feng Jiang, Bo-Le Jiang, Mei Yang, San Liu, Jiao Liu, Xiao-Xia Liang, Xian-Fang Bai, Dong-Jie Tang, Guang-Tao Lu, Yong-Qiang He, Di-Qiu Yu and Ji-Liang Tang

 

Abstract:

It is well known that the type III secretion system (T3SS) and type III (T3) effectors are essential for the pathogenicity of most bacterial phytopathogens and that the expression of T3SS and T3 effectors is suppressed in rich media but induced in minimal media and plants. To facilitate in-depth studies on T3SS and T3 effectors, it is crucial to establish a medium for T3 effector expression and secretion. Xanthomonas campestris pv. campestris (Xcc) is a model bacterium for studying plant-pathogen interactions. To date no medium for Xcc T3 effector secretion has been defined. Here, we compared four minimal media (MME, MMX, XVM2, and XOM2) which are reported for T3 expression induction in Xanthomonasspp. and found that MME is most efficient for expression and secretion ofXcc T3 effectors. By optimization of carbon and nitrogen sources and pH value based on MME, we established XCM1 medium, which is about 3 times stronger than MME for Xcc T3 effectors secretion. We further optimized the concentration of phosphate, calcium, and magnesium in XCM1 and found that XCM1 with a lower concentration of magnesium (renamed as XCM2) is about 10 times as efficient as XCM1 (meanwhile, about 30 times stronger than MME). Thus, we established an inducing medium XCM2 which is preferred for T3 effector secretion in Xcc.

Freddy Monteiro's insight:

This has to be tested!
If anyone already used it or is about to, please be so kind to leave a comment here =) I would do it myself... if I could.

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Rescooped by Freddy Monteiro from MycorWeb Plant-Microbe Interactions
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A Promiscuous Intermediate Underlies the Evolution of LEAFY DNA Binding Specificity

A Promiscuous Intermediate Underlies the Evolution of LEAFY DNA Binding Specificity | Plants&Bacteria | Scoop.it

Scooped from: Science, 2014

Authors: Camille Sayou, Marie Monniaux, Max H. Nanao, Edwige Moyroud, Samuel F. Brockington, Emmanuel Thévenon, Hicham Chahtane, Norman Warthmann, Michael Melkonian, Yong Zhang, Gane Ka-Shu Wong, Detlef Weigel, François Parcy and Renaud Dumas.

 

Abstract

Transcription factors (TFs) are key players in evolution. Changes affecting their function can yield novel life forms but may also have deleterious effects. Consequently, gene duplication events that release one gene copy from selective pressure are thought to be the common mechanism by which TFs acquire new activities. Here, we show that LEAFY, a major regulator of flower development and cell division in land plants, underwent changes to its DNA binding specificity, even though plant genomes generally contain a single copy of the LEAFY gene. We examined how these changes occurred at the structural level and identify an intermediate LEAFY form in hornworts that appears to adopt all different specificities. This promiscuous intermediate could have smoothed the evolutionary transitions, thereby allowing LEAFY to evolve new binding specificities while remaining a single-copy gene.


Via Francis Martin
Freddy Monteiro's insight:

This is so elegant!

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A potential source of late blight resistance for potato breeding

A potential source of late blight resistance for potato breeding | Plants&Bacteria | Scoop.it

Scooped from: Plant Cell Reports, 2013

Authors: P. Smyda, H. Jakuczun, K. Dębski, J. Śliwka, R. Thieme, M. Nachtigall, I. Wasilewicz-Flis and E. Zimnoch-Guzowska 

 

Summary:
Key message
Phytophthora infestans resistant somatic hybrids of S. × michoacanum (+) S. tuberosum and autofused 4 x S. × michoacanum were obtained. Our material is promising to introgress resistance from S. × michoacanum into cultivated potato background.
Abstract
Solanum × michoacanum (Bitter.) Rydb. (mch) is a wild diploid (2n = 2x = 24) potato species derived from spontaneous cross of S. bulbocastanum and S. pinnatisectum. This hybrid is a 1 EBN (endosperm balance number) species and can cross effectively only with other 1 EBN species. Plants of mch are resistant to Phytophthora infestans (Mont) de Bary. To introgress late blight resistance genes from mch into S. tuberosum (tbr), genepool somatic hybridization between mch and susceptible diploid potato clones (2n = 2x = 24) or potato cultivar Rywal (2n = 4x = 48) was performed. In total 18,775 calli were obtained from postfusion products from which 1,482 formed shoots. The Simple Sequence Repeat (SSR), Cleaved Amplified Polymorphic Sequences (CAPS) and Random Amplified Polymorphic DNA (RAPD) analyses confirmed hybrid nature of 228 plants and 116 autofused 4x mch. After evaluation of morphological features, flowering, pollen stainability, tuberization and ploidy level, 118 somatic hybrids and 116 autofused 4x mch were tested for late blight resistance using the detached leaf assay. After two seasons of testing three somatic hybrids and 109 4x mch were resistant. Resistant forms have adequate pollen stainability for use in crossing programme and are a promising material useful for introgression resistance from mch into the cultivated potato background.

Freddy Monteiro's insight:

For a deeper analysis of this publication, may I recommend the followind readings:


- Orczyk et al. Somatic hybrids of Solanum tuberosum – application to genetics and breeding (2003). Plant Cell, Tissue and Organ Culture 74; 1 1-13 http://link.springer.com/article/10.1023%2FA%3A1023396405655

 

- Fock et al. Resistance to bacterial wilt in somatic hybrids between Solanum tuberosum and Solanum phureja (2000). Plant Science 160 165-176 https://www.google.pt/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CCwQFjAA&url=http%3A%2F%2Fwww.researchgate.net%2Fpublication%2F12164636_Resistance_to_bacterial_wilt_in_somatic_hybrids_between_Solanum_tuberosum_and_Solanum_phureja%2Ffile%2F79e4150927a94227d6.pdf&ei=9f_4UtWlK9Gn0wXoz4DYBA&usg=AFQjCNH0s0upJE5nYAS-KgqUhy5oWirJAw

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Freddy Monteiro's comment, February 10, 11:42 AM
Orczyk etal. Somatic hybrids of Solanum tuberosum – application to genetics and breeding (2003). Plant Cell, Tissue and Organ Culture 74; 1 1-13 http://link.springer.com/article/10.1023%2FA%3A1023396405655
Christophe Jacquet's comment, February 10, 11:55 AM
Thanks!
Freddy Monteiro's comment, February 10, 12:06 PM
Had a hard time placing comments. Just wanted to have those papers here for future reference and discussions.
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Potential Interactions between Salmonella enterica and Ralstonia solanacearum in Tomato Plants - MSc Thesis + Res. Article

MSc Thesis Author: Stephanie Kay Pollard

Institute: Virginia Polytechnic Institute and State University

Sci. Comitee: Steven L. Rideout, Jeri D. Barak, Renee R. Boyer, Elizabeth A. Grabau and Mark S. Reiter

 

Abstract: 

Over the past decade, the Eastern Shore of Virginia (ESV) has been implicated in at least four outbreaks of Salmonellosis associated with tomato all originating from the same strain, Salmonella enterica serovar Newport.  In addition to S. Newport contamination, the devastating plant disease, bacterial wilt, caused by the phytopathogen Ralstonia solanacearum threatens the sustainability of ESV tomato production.  Bacterial wilt is present in most ESV tomato fields and causes devastating yield losses each year.  Due to the ESV\'s endemic population of R. solanacearum and S. Newport, the relationship between the two pathogens is of interest and has never been investigated.  Two separate studies were conducted to assess the relationship between these two bacteria.  One study consisted of a series of greenhouse trials that involved root-dip inoculations of tomato plants with one of four treatments: 1) S. Newport, 2) R. solanacearum, 3) a co-inoculation of S. Newport + R. solanacearum, and 4) a control group with no inoculation.    Leaf, stem, and fruit samples were collected from the plants and S. enterica presence from the internal tissues was observed.  S. enterica was recovered from a low percentage of fruit and leaf samples.  There were significantly more stem samples from plants co-inoculated with S. Newport + R. solanacearum positive for S. enterica (17.46%) than from other treatments.  Another study examined the relationship between the two bacteria via vacuum infiltration inoculations of tomato fruit collected from commercial production fields on the ESV with S. Newport.  Tomato fruit were collected from plants expressing symptoms of bacterial wilt (symptomatic) and plants not expressing bacterial wilt symptoms (asymptomatic).  After fruit infiltration with S. Newport, recovery concentration of S. enterica from internal tissues was measured.  S. enterica populations were greater in fruit originating from asymptomatic (5.15 log CFU/g) versus symptomatic (4.91 log CFU/g) plants across five studies.  Fruit collected from asymptomatic plants had a significantly higher internal pH (4.60) than fruit collected from symptomatic plants (4.37).  These results suggest that R. solanacearum can influence S. enterica survival and transportation throughout the internal tissues of tomato plants as well as the influence internal tomato fruit pH, which could potentially impact S. Newport survival in the fruit.

 

Recently published article:

http://www.ncbi.nlm.nih.gov/pubmed/24490928?dopt=Abstract

 

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Freddy Monteiro's comment, February 5, 7:21 AM
This article is a great fit for the topic "Plants and Bacteria"
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A Synthetic Community Approach Reveals Plant Genotypes Affecting the Phyllosphere Microbiota

A Synthetic Community Approach Reveals Plant Genotypes Affecting the Phyllosphere Microbiota | Plants&Bacteria | Scoop.it

Scooped from: PLOS Genetics, 2014.

Authors: Natacha Bodenhausen, Miriam Bortfeld-Miller, Martin Ackermann and Julia A. Vorholt.

 

Summary:

The identity of plant host genetic factors controlling the composition of the plant microbiota and the extent to which plant genes affect associated microbial populations is currently unknown. Here, we use a candidate gene approach to investigate host effects on the phyllosphere community composition and abundance. To reduce the environmental factors that might mask genetic factors, the model plant Arabidopsis thaliana was used in a gnotobiotic system and inoculated with a reduced complexity synthetic bacterial community composed of seven strains representing the most abundant phyla in the phyllosphere. From a panel of 55 plant mutants with alterations in the surface structure, cell wall, defense signaling, secondary metabolism, and pathogen recognition, a small number of single host mutations displayed an altered microbiota composition and/or abundance. Host alleles that resulted in the strongest perturbation of the microbiota relative to the wild-type were lacs2 and pec1. These mutants affect cuticle formation and led to changes in community composition and an increased bacterial abundance relative to the wild-type plants, suggesting that different bacteria can benefit from a modified cuticle to different extents. Moreover, we identified ein2, which is involved in ethylene signaling, as a host factor modulating the community's composition. Finally, we found that different Arabidopsis accessions exhibited different communities, indicating that plant host genetic factors shape the associated microbiota, thus harboring significant potential for the identification of novel plant factors affecting the microbiota of the communities.

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The Role of Autophagy in Chloroplast Degradation and Chlorophagy in Immune Defenses during Pst DC3000 (AvrRps4) Infection

The Role of Autophagy in Chloroplast Degradation and Chlorophagy in Immune Defenses during Pst DC3000 (AvrRps4) Infection | Plants&Bacteria | Scoop.it

Scooped from: PLOS One, 2014

Authors: Junjian Dong and Wenli Chen


Summary:

Background

Chlorosis of leaf tissue normally observed during pathogen infection may result from the degradation of chloroplasts. There is a growing evidence to suggest that the chloroplast plays a significant role during pathogen infection. Although most degradation of the organelles and cellular structures in plants is mediated by autophagy, its role in chloroplast catabolism during pathogen infection is largely unknown.

Results

In this study, we investigated the function of autophagy in chloroplast degradation during avirulent Pst DC3000 (AvrRps4) infection. We examined the expression of defensive marker genes and suppression of bacterial growth using the electrolyte leakage assay in normal light (N) and low light (L) growing environments of wild-type and atg5-1 plants during pathogen treatment. Stroma-targeted GFP proteins (CT-GFP) were observed with LysoTracker Red (LTR) staining of autophagosome-like structures in the vacuole. The results showed that Arabidopsis expressed a significant number of small GFP-labeled bodies when infected with avirulent Pst DC3000 (AvrRps4). While barely detectable, there were small GFP-labeled bodies in plants with the CT-GFP expressing atg5-1 mutation. The results showed that chloroplast degradation depends on autophagy and this may play an important role in inhibiting pathogen growth.

Conclusion

Autophagy plays a role in chloroplast degradation in Arabidopsis during avirulent Pst DC3000 (AvrRps4) infection. Autophagy dependent chloroplast degradation may be the primary source of reactive oxygen species (ROS) as well as the pathogen-response signaling molecules that induce the defense response.


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Identification of Genes Differentially Expressed between Resistant and Susceptible Tomato Lines during Time-Course Interactions with Xanthomonas perforans Race T3

Identification of Genes Differentially Expressed between Resistant and Susceptible Tomato Lines during Time-Course Interactions with Xanthomonas perforans Race T3 | Plants&Bacteria | Scoop.it

Scooped from: PLOS One, 2014

Authors: Heshan Du, Wenhui Li, Yuqing Wang, Wencai Yang.


Abstract:

Bacterial spot caused by several Xanthomonas sp. is one of the most devastating diseases in tomato (Solanum lycopersicum L.). The genetics of hypersensitive resistance to X. perforans race T3 has been intensively investigated and regulatory genes during the infection of race T3 have been identified through transcriptional profiling. However, no work on isolating regulatory genes for field resistance has been reported. In this study, cDNA-amplified fragment length polymorphism technique was used to identify differentially expressed transcripts between resistant tomato accession PI 114490 and susceptible variety OH 88119 at 3, 4 and 5 days post-inoculation of the pathogen. Using 256 selective primer combinations, a total of 79 differentially expressed transcript-derived fragments (TDFs) representing 71 genes were obtained. Of which, 60 were up-regulated and 4 were down-regulated in both tomato lines, 4 were uniquely up-regulated and 2 were uniquely down-regulated in PI 114490, and 1 was specifically up-regulated in OH 88119. The expression patterns of 19 representative TDFs were further confirmed by semi-quantitative and/or quantitative real time RT-PCR. These results suggested that the two tomato lines activated partly similar defensive mechanism in response to race T3 infection. The data obtained here will provide some fundamental information for elucidating the molecular mechanism of response to race T3 infection in tomato plants with field resistance.

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The Carboxy-terminus of BAK1 regulates kinase activity and is required for normal growth of Arabidopsis

The Carboxy-terminus of BAK1 regulates kinase activity and is required for normal growth of Arabidopsis | Plants&Bacteria | Scoop.it

Scooped from: Front. Plant Sci., 2014

Authors: Man-Ho Oh, Xuejun Wang, Sang Yeol Kim, Xia Wu, Steven D. Clouse and Steven C. Huber

 

Abstract:

Binding of brassinolide to the brassinosteroid-insenstive 1(BRI1) receptor kinase promotes interaction with its co-receptor, BRI1-associated receptor kinase 1 (BAK1). Juxtaposition of the kinase domains that occurs then allows reciprocal transphosphorylation and activation of both kinases, but details of that process are not entirely clear. In the present study we show that the carboxy (C)-terminal polypeptide of BAK1 may play a role. First, we demonstrate that the C-terminal domain is a strong inhibitor of the transphosphorylation activity of the recombinant BAK1 cytoplasmic domain protein. However, recombinant BAK1 lacking the C-terminal domain is unable to transactivate the peptide kinase activity of BRI1 in vitro. Thus, the C-terminal domain may play both a positive and negative role. Interestingly, a synthetic peptide corresponding to the full C-terminal domain (residues 576–615 of BAK1) interacted with recombinant BRI1 in vitro, and that interaction was enhanced by phosphorylation at the Tyr-610 site. Expression of a BAK1 C-terminal domain truncation (designated BAK1-ΔCT-Flag) in transgenic Arabidopsis plants lacking endogenous bak1 and its functional paralog, bkk1, produced plants that were wild type in appearance but much smaller than plants expressing full-length BAK1-Flag. The reduction in growth may be attributed to a partial inhibition of BR signaling in vivo as reflected in root growth assays but other factors are likely involved as well. Our working model is that in vivo, the inhibitory action of the C-terminal domain of BAK1 is relieved by binding to BRI1. However, that interaction is not essential for BR signaling, but other aspects of cellular signaling are impacted when the C-terminal domain is truncated and result in inhibition of growth. These results increase the molecular understanding of the C-terminal domain of BAK1 as a regulator of kinase activity that may serve as a model for other receptor kinases.

 

Freddy Monteiro's insight:

Tyr phosphorilation of BAK1 Tyr residues upon deletion of C-terminal domain and interaction with BRI1

 

It may be interesting to read this beforehand:

Oh et al. Tyrosine phosphorylation of the BRI1 receptor kinase emerges as a component of brassinosteroid signaling in Arabidopsis. PNAS 2009. http://www.pnas.org/content/106/2/658.long

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A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation

A Bacterial Tyrosine Phosphatase Inhibits Plant Pattern Recognition Receptor Activation | Plants&Bacteria | Scoop.it

Scooped from: Science, 2014

Authors: Alberto P. Macho, Benjamin Schwessinger, Vardis Ntoukakis, Alexandre Brutus, Cécile Segonzac, Sonali Roy, Yasuhiro Kadota, Man-Ho Oh, Jan Sklenar, Paul Derbyshire, Rosa Lozano-Durán, Frederikke Gro Malinovsky, Jacqueline Monaghan, Frank L. Menke, Steven C. Huber, Sheng Yang He and Cyril Zipfel.

 

Summary: 

Innate immunity relies on the perception of pathogen-associated molecular patterns (PAMPs) by pattern-recognition receptors (PRRs) located on the host cell’s surface. Many plant PRRs are kinases. Here, we report that the Arabidopsis receptor kinase EF-TU RECEPTOR EFR, which perceives the elf18 peptide derived from bacterial elongation factor Tu, is activated upon ligand binding by phosphorylation on its tyrosine residues. Phosphorylation of a single tyrosine residue, Y836, is required for activation of EFR and downstream immunity to the phytopathogenic bacterium Pseudomonas syringae. A tyrosine phosphatase, HopAO1, secreted by P. syringae, reduces EFR phosphorylation and derails subsequent immune responses. Thus host and pathogen battle to take control of PRR tyrosine phosphorylation used to initiate anti-bacterial immunity.

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Jim Alfano's curator insight, March 13, 6:21 PM

Very interesting finding - A long sought target of the HopAO1 effector. HopAO1 also suppresses ETI - so additional targets remain undiscovered.

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Genome-free Plastids on Plants - 3, 2, 1, Dispute! by Ed Yong

Genome-free Plastids on Plants - 3, 2, 1, Dispute! by Ed Yong | Plants&Bacteria | Scoop.it

The Scientist

"Plants Without Plastid Genomes".

"Two independent teams point to different plants that may have lost their plastid genomes".

By Ed Yong

http://www.the-scientist.com/?articles.view/articleNo/39313/title/Plants-Without-Plastid-Genomes/

 

 

D. R. Smith and R. W. Lee, “A plastid without a genome: evidence from the nonphotosynthetic green alga Polytomella,” Plant Physiology, doi:10.1104/pp.113.233718, 2014.

http://www.plantphysiol.org/content/early/2014/02/21/pp.113.233718.abstract

 

J. Molina et al., “Possible loss of the chloroplast genome in the parasitic flowering plant Rafflesia lagascae (Rafflesiaceae),” Molecular Biology and Evolution, doi:10.1093/molbev/msu051, 2014.

http://mbe.oxfordjournals.org/content/early/2014/01/23/molbev.msu051.abstract

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The Bacterial Effector HopX1 Targets JAZ Transcriptional Repressors to Activate Jasmonate Signaling and Promote Infection in Arabidopsis

The Bacterial Effector HopX1 Targets JAZ Transcriptional Repressors to Activate Jasmonate Signaling and Promote Infection in Arabidopsis | Plants&Bacteria | Scoop.it

/via KamounLab scoop.it

Scooped from: PLOS Biology, 2014

Authors: Selena Gimenez-Ibañez, Marta Boter, Gemma Fernández-Barbero, Andrea Chini, John P. Rathjen, Roberto Solano

 

Abstract:

Pathogenicity of Pseudomonas syringae is dependent on a type III secretion system, which secretes a suite of virulence effector proteins into the host cytoplasm, and the production of a number of toxins such as coronatine (COR), which is a mimic of the plant hormone jasmonate-isoleuce (JA-Ile). Inside the plant cell, effectors target host molecules to subvert the host cell physiology and disrupt defenses. However, despite the fact that elucidating effector action is essential to understanding bacterial pathogenesis, the molecular function and host targets of the vast majority of effectors remain largely unknown. Here, we found that effector HopX1 fromPseudomonas syringae pv. tabaci (Pta) 11528, a strain that does not produce COR, interacts with and promotes the degradation of JAZ proteins, a key family of JA-repressors. We show that hopX1 encodes a cysteine protease, activity that is required for degradation of JAZs by HopX1. HopX1 associates with JAZ proteins through its central ZIM domain and degradation occurs in a COI1-independent manner. Moreover, ectopic expression of HopX1 in Arabidopsisinduces the expression of JA-dependent genes, represses salicylic acid (SA)-induced markers, and complements the growth of a COR-deficient P. syringae pv. tomato (Pto) DC3000 strain during natural bacterial infections. Furthermore, HopX1 promoted susceptibility when delivered by the natural type III secretion system, to a similar extent as the addition of COR, and this effect was dependent on its catalytic activity. Altogether, our results indicate that JAZ proteins are direct targets of bacterial effectors to promote activation of JA-induced defenses and susceptibility in Arabidopsis. HopX1 illustrates a paradigm of an alternative evolutionary solution to COR with similar physiological outcome.

 


Via Kamoun Lab @ TSL
Freddy Monteiro's insight:

Congratulations to Selena for this elegant story and for seeking for the best advice one can only wish of having. Extended congratulations for the rest of the team at CNB (MAdrid) for the efforts put on this.

 

Another great publication to go side by side with this one:

Üstün et al. The Xanthomonas campestris Type III Effector XopJ Targets the Host Cell Proteasome to Suppress Salicylic-Acid Mediated Plant Defence. PLOS Pathogens 2013.

http://dx.plos.org/10.1371/journal.ppat.1003427

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Freddy Monteiro's comment, February 20, 2:28 PM
Another great publication to go side by side with this one:<br>Üstün et al. The Xanthomonas campestris Type III Effector XopJ Targets the Host Cell Proteasome to Suppress Salicylic-Acid Mediated Plant Defence. PLOS Pathogens 2013. http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003427
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Multigeneration analysis reveals the inheritance, specificity, and patterns of CRISPR/Cas-induced gene modifications in Arabidopsis

Multigeneration analysis reveals the inheritance, specificity, and patterns of CRISPR/Cas-induced gene modifications in Arabidopsis | Plants&Bacteria | Scoop.it

/via T. Mucyn (thanks!)

Scooped from: PNAS, 2014

Authors: Zhengyan Feng, Yanfei Mao, Nanfei Xu, Botao Zhang, Pengliang Wei, Dong-Lei Yang, Zhen Wang, Zhengjing Zhang, Rui Zheng, Lan Yang, Liang Zeng, Xiaodong Liu, and Jian-Kang Zhu.

 

Abstract:

The CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) system has emerged as a powerful tool for targeted gene editing in many organisms, including plants. However, all of the reported studies in plants focused on either transient systems or the first generation after the CRISPR/Cas system was stably transformed into plants. In this study we examined several plant generations with seven genes at 12 different target sites to determine the patterns, efficiency, specificity, and heritability of CRISPR/Cas-induced gene mutations or corrections in Arabidopsis. The proportion of plants bearing any mutations (chimeric, heterozygous, biallelic, or homozygous) was 71.2% at T1, 58.3% at T2, and 79.4% at T3 generations. CRISPR/Cas-induced mutations were predominantly 1 bp insertion and short deletions. Gene modifications detected in T1 plants occurred mostly in somatic cells, and consequently there were no T1 plants that were homozygous for a gene modification event. In contrast, ∼22% of T2 plants were found to be homozygous for a modified gene. All homozygotes were stable to the next generation, without any new modifications at the target sites. There was no indication of any off-target mutations by examining the target sites and sequences highly homologous to the target sites and by in-depth whole-genome sequencing. Together our results show that the CRISPR/Cas system is a useful tool for generating versatile and heritable modifications specifically at target genes in plants.

 

Significance:

The CRISPR (clustered regularly interspaced short palindromic repeat)/Cas (CRISPR-associated) system has been used to generate targeted gene editing in plants. However, it is not known whether CRISPR/Cas-induced gene modifications in plants occur in somatic cells only or whether some or all of the modifications can enter the germ line to become heritable. Through systematic and multigenerational analysis, this study demonstrates that although the majority of gene modifications detected in the first generation CRISPR/Cas transgenic Arabidopsis plants were somatic mutations only, heritable mutations could be found in subsequent generations. In addition, deep sequencing of CRISPR/Cas-modified Arabidopsis genomes did not detect any off-targets. The work demonstrates that the CRISPR/Cas method can effectively create specific gene modifications in planta that are stably transmitted through the germ line to future generations.

Freddy Monteiro's insight:

This is key: "[modifications are] stably transmitted through the germ line to future generations"

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New website serves as a portal for Nicotiana benthamiana experimental resources

New website serves as a portal for Nicotiana benthamiana experimental resources | Plants&Bacteria | Scoop.it

Scientists from BTI and seven other institutions are collaborating on a project to improve the genome sequence of Nicotiana benthamiana and develop software tools for its analysis. As part of this effort, a website has been developed that serves as a portal for bioinformatics and experimental resources for this plant species: http://bti.cornell.edu/nicotiana-benthamiana/


Nicotiana benthamiana is widely used for experimentation because it is particularly amenable to virus-induced gene silencing (VIGS) which enables functional characterization of genes and for transient expression of proteins using Agrobacterium infiltration of its large leaves.

 

The website provides various bioinformatics resources including a link for accessing the draft genome sequence of N. benthamiana which was published in 2012. The genome sequence can be searched using a BLAST Tool provided on the website and ftp links allow downloading of the sequence, its gene annotation and a database of its predicted proteome.

A 'VIGS Tool', developed by Dr. Noe Fernandez (BTI) and available on the website enables the rapid identification of a DNA sequence that allows effective gene silencing and avoids silencing of non-target genes. A complementary tool for the design of artificial microRNAs and additional genome resources are available from the University of Sydney and a link is provided to that website.

 

Other links on the website provide publications related to the history, taxonomy and use of N. benthamiana and protocols for performing VIGS, Agrobacterium-infiltration, and assays of the plant immune system.

 

The N. benthamiana genome project and website are the result of a collaboration between scientists from BTI, USDA-ARS, Cold Spring Harbor Laboratory, National Institute of Plant Genome Research (India), Samuel Roberts Noble Foundation, University of Kentucky, and Université de Sherbrooke (Canada).

The N. benthamiana genome project and the website are supported by BTI Innovation Funds and by National Science Foundation grant IOS-1025642.

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Protein intrinsic disorder in plants

Protein intrinsic disorder in plants | Plants&Bacteria | Scoop.it

/via João Teixeira (thank's!!)

Scooped from: Frontiers in Plant Science, 2013

Authors: Florencio Pazos, Natalia Pietrosemoli, Juan A. García-Martín and Roberto Solano

 

Abstract:

To some extent contradicting the classical paradigm of the relationship between protein 3D structure and function, now it is clear that large portions of the proteomes, especially in higher organisms, lack a fixed structure and still perform very important functions. Proteins completely or partially unstructured in their native (functional) form are involved in key cellular processes underlain by complex networks of protein interactions. The intrinsicconformational flexibility of these disordered proteins allows them to bind multiple partners in transient interactions of high specificity and low affinity. In concordance, in plants this type of proteins has been found in processes requiring these complex and versatile interaction networks. These include transcription factor networks, where disordered proteins act as integrators of different signals or link different transcription factor subnetworks due to their ability to interact (in many cases simultaneously) with different partners. Similarly, they also serve as signal integrators in signaling cascades, such as those related to response to external stimuli. Disordered proteins have also been found in plants in many stress-response processes, acting as protein chaperones or protecting other cellular components and structures. In plants, it is especially important to have complex and versatile networks able to quickly and efficiently respond to changing environmental conditions since these organisms cannot escape and have no other choice than adapting to them. Consequently, protein disorder can play an especially important role in plants, providing them with a fast mechanism to obtain complex, interconnected and versatile molecular networks.

Freddy Monteiro's insight:

In the image:

IUPRED disorder prediction of the A. thaliana NAC94 TF  C-terminal domain (threshold 0.5).

 

IUPRED: http://iupred.enzim.hu/

ANCHOR: http://anchor.enzim.hu/

 

Interesting ANCHOR applications: 

http://www.ncbi.nlm.nih.gov/pubmed/21541066

http://www.ncbi.nlm.nih.gov/pubmed/23056474

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Comparative Effect of Low Temperature on Virulence and Twitching Motility of Ralstonia solanacearum Strains Present in Florida

Comparative Effect of Low Temperature on Virulence and Twitching Motility of Ralstonia solanacearum Strains Present in Florida | Plants&Bacteria | Scoop.it

Scooped from: Phytopathology, 2012

Authors: Ana M. Bocsanczy, Ute C. M. Achenbach, Arianna Mangravita-Novo, Jeanne M. F. Yuen, and David J. Norman

 

Abstract

Ralstonia solanacearum causes bacterial wilt on a wide range of plant hosts. Most strains of R. solanacearum are nonpathogenic below 20°C; however, Race 3 Biovar 2 (R3B2) strains are classified as quarantine pathogens because of their ability to infect crops, cause disease, and survive in temperate climates. We have identified race 1 biovar 1 Phylotype IIB Sequevar 4 strains present in Florida which were able to infect and produce wilt symptoms on potato and tomato at 18°C. Moreover they infected tomato plants at rates similar to strains belonging to R3B2. We determined that strains naturally nonpathogenic at 18°C were able to multiply, move in planta, and cause partial wilt when inoculated directly into the stem, suggesting that low temperature affects virulence of strains differently at early stages of infection. Bacterial growth in vitro was delayed at low temperatures, however it was not attenuated. Twitching motility observed on growing colonies was attenuated in nonpathogenic strains at 18°C, while not affected in the cool virulent ones. Using pilQ as a marker to evaluate the relative expression of the twitching activity of R. solanacearumstrains, we confirmed that cool virulent strains maintained a similar level of pilQ expression at both temperatures, while in nonpathogenic strains pilQ was downregulated at 18°C.

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Towards the identification of novel R. solanacearum elicitors - PhD Thesis

Author: Eric Melzer

Title: Characterisation of a new bacterial elicitor from Ralstonia solanacearum in Arabidopsis thaliana

Institute: Eberhard Karls Universität Tübingen

 

Abstract:

Plant innate immunity is activated either upon perception of microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs) or upon resistance (R) protein-mediated recognition of pathogen race-specific effector molecules. MAMP-triggered immunity (MTI) constitutes the primary plant immune response that has evolved to recognize invariant structures of microbial surfaces. Although several cell surface components of bacteria, fungi or oomycetes have been shown to act as MAMPs that trigger immune responses in various plant species, the enormous non-self recognition capacities of plants are not at all explored. 
To find new proteinaceous MAMPs we used crude protein preparations of the phytopathogenic gram-negative bacterium Ralstonia solanacearum. We found a proteinase-sensitive and heat stable MAMP activity in these crude extracts which triggers immune responses in the model plant Arabidopsis thaliana such as ethylene production, PR1 induction, callose deposition and medium alkalinization. We further fractionated the bacterial proteins by different chromatography strategies such as ion exchange chromatography. By gel filtration chromatography we estimated a probable elicitor size of 30 kDA or less.
Besides A. thaliana the R. solanacearum elicitor also triggered defense related responses in N. benthamiana and the tomato MsK8.

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