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Rescooped by tianxing84 from Trends in MPMI
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The Tomato Fni3 Lysine-63–Specific Ubiquitin-Conjugating Enzyme and Suv Ubiquitin E2 Variant Positively Regulate Plant Immunity

The Tomato Fni3 Lysine-63–Specific Ubiquitin-Conjugating Enzyme and Suv Ubiquitin E2 Variant Positively Regulate Plant Immunity | tomato | Scoop.it

The activation of an immune response in tomato (Solanum lycopersicum) against Pseudomonas syringae relies on the
recognition of E3 ligase–deficient forms of AvrPtoB by the host protein kinase, Fen. To investigate the mechanisms by which
Fen-mediated immunity is regulated, we characterize in this study a Fen-interacting protein, Fni3, and its cofactor,
S. lycoperiscum Uev (Suv). Fni3 encodes a homolog of the Ubc13-type ubiquitin-conjugating enzyme that catalyzes
exclusively Lys-63–linked ubiquitination, whereas Suv is a ubiquitin-conjugating enzyme variant. The C-terminal region of Fen
was necessary for interaction with Fni3, and this interaction was required for cell death triggered by overexpression of Fen in
Nicotiana benthamiana leaves. Fni3 was shown to be an active E2 enzyme, but Suv displayed no ubiquitin-conjugating
activity; Fni3 and Suv together directed Lys-63–linked ubiquitination. Decreased expression of Fni3, another tomato Ubc13
homolog, Sl-Ubc13-2, or Suv in N. benthamiana leaves diminished cell death associated with Fen-mediated immunity and cell
death elicited by several other resistance (R) proteins and their cognate effectors. We also discovered that coexpression of
Fen and other R proteins/effectors with a Fni3 mutant that is compromised for ubiquitin-conjugating activity diminished the
cell death. These results suggest that Fni3/Sl-Ubc13-2 and Suv regulate the immune response mediated by Fen and other R
proteins through Lys-63–linked ubiquitination.


Via Suayib Üstün, CP
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Rescooped by tianxing84 from Plant-microbe interaction
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Simultaneous application of heat, drought and virus to Arabidopsis thaliana plants reveals significant shifts in signaling networks

Simultaneous application of heat, drought and virus to Arabidopsis thaliana plants reveals significant shifts in signaling networks | tomato | Scoop.it

Scooped from: Plant Physiology, 2013 (via Jennifer Mach's scoopit)

Authors: Christian Maximilian Prasch and Uwe Sonnewald

 

Summary:

Considering global climate changes, incidences of combined drought and heat stress are likely to increase in the future and will considerably influence plant-pathogen interactions. Until now, little is known about plants exposed to simultaneously occurring abiotic and biotic stresses. To shed some light on molecular plant responses to multiple stress factors, a versatile multi-factorial test system, allowing simultaneous application of heat, drought and virus stress, was developed. Comparative analysis of single, double and triple stress responses by transcriptome and metabolome analysis revealed that gene expression under multi-factorial stress is not predictable from single stress treatments. Hierarchical cluster and principal component analysis identified heat as the major stress factor clearly separating heat-stressed from non-heat stressed plants. We identified 11 genes differentially regulated in all stress combinations as well as 23 genes specifically-regulated under triple stress. Furthermore, we showed that virus treated plants displayed enhanced expression of defense genes, which was abolished in plants additionally subjected to heat and drought stress. Triple stress also reduced expression of genes involved in the R-mediated disease response and increased the cytoplasmic protein response which was not seen under single stress conditions. These observations suggested that abiotic stress factors significantly altered TuMV-specific signaling networks which lead to a deactivation of defense responses and a higher susceptibility of plants. Collectively, our transcriptome and metabolome data provide a powerful resource to study plant responses during multi-factorial stress and allows identifying metabolic processes and functional networks involved in tripartite interactions of plants with their environment.


Via Jennifer Mach, Freddy Monteiro, Suayib Üstün
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Developmental Cell - Symplastic Intercellular Connectivity Regulates Lateral Root Patterning


Via PMG
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PMG's curator insight, July 15, 2013 6:53 PM

changes in symplastic connectivity accompany and regulate lateral root organogenesis in Arabidopsis. This connectivity is dependent upon callose deposition around PD affecting molecular flux through the channel. Two plasmodesmal-localized β-1,3 glucanases (PdBGs) were identified that regulate callose accumulation and the number and distribution of lateral roots. The fundamental role of PD-associated callose in this process was illustrated by the induction of similar phenotypes in lines with altered callose turnover. Our results show that regulation of callose and cell-to-cell connectivity is critical in determining the pattern of lateral root formation, which influences root architecture and optimal plant performance.

Rescooped by tianxing84 from plant cell genetics
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Comparison of Intracanopy Light-emitting Diode Towers and Overhead High-pressure Sodium Lamps for Supplemental Lighting of Greenhouse-grown Tomatoes

Comparison of Intracanopy Light-emitting Diode Towers and Overhead High-pressure Sodium Lamps for Supplemental Lighting of Greenhouse-grown Tomatoes | tomato | Scoop.it

Electric supplemental lighting can account for a significant proportion of total greenhouse energy costs. Thus, the objectives of this study were to compare high-wire tomato (Solanum lycopersicum) production with and without supplemental lighting and to evaluate two different lighting positions + light sources [traditional high-pressure sodium (HPS) overhead lighting (OHL) lamps vs. light-emitting diode (LED) intracanopy lighting (ICL) towers] on several production and energy-consumption parameters for two commercial tomato cultivars. Results indicated that regardless of the lighting position + source, supplemental lighting induced early fruit production and increased node number, fruit number (FN), and total fruit fresh weight (FW) for both cultivars compared with unsupplemented controls for a winter-to-summer production period. Furthermore, no productivity differences were measured between the two supplemental lighting treatments. The energy-consumption metrics indicated that the electrical conversion efficiency for light-emitting intracanopy lighting (LED-ICL) into fruit biomass was 75% higher than that for HPS-OHL. Thus, the lighting cost per average fruit grown under the HPS-OHL lamps was 403% more than that of using LED-ICL towers. Although no increase in yield was measured using LED-ICL, significant energy savings for lighting occurred without compromising fruit yield.


Via Jean-Pierre Zryd
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Rescooped by tianxing84 from Plant Biology Teaching Resources (Higher Education)
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Three in Development on pattern formation and polarity

Three in Development on pattern formation and polarity | tomato | Scoop.it

If you love patterning like I love patterning, you might be interested in these three recent articles in Development.

 

Here's a Hypothesis:

 

"An intracellular partitioning-based framework for tissue cell polarity in plants and animals" http://dev.biologists.org/content/140/10/2061.abstract

 

"We propose that a fundamental building block for tissue cell polarity is the process of intracellular partitioning,which can establish individual cell polarity in the absence of asymmetric cues."

 

 

And another Hypothesis:

 

"Polar auxin transport: models and mechanisms"

http://dev.biologists.org/content/140/11/2253.abstract

 

"Here we propose a new mathematical framework for the analysis of polar auxin transport and present a detailed mathematical analysis of published models."

 

And a Open Access research article on leaf polarity, running title

"ARF3 is a direct target of AS1"

http://dev.biologists.org/content/140/9/1958.short

(Currently one of the most-read articles in Development)


Via Mary Williams
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Recent advances in tomato functional genomics: utilization of VIGS

Recent advances in tomato functional genomics: utilization of VIGS | tomato | Scoop.it

Tomato unquestionably occupies a significant position in world vegetable production owing to its world-wide consumption. The tomato genome sequencing efforts being recently concluded, it becomes more imperative to recognize important functional genes from this treasure of generated information for improving tomato yield. While much progress has been made in conventional tomato breeding, post-transcriptional gene silencing (PTGS) offers an alternative approach for advancement of tomato functional genomics. In particular, virus-induced gene silencing (VIGS) is increasingly being used as rapid, reliable, and lucrative screening strategy to elucidate gene function. In this review, we focus on the recent advancement made through exploiting the potential of this technique for manipulating different agronomically important traits in tomato by discussing several case studies.

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Cell Host and Microbe - Xanthomonas Type III Effector XopD Desumoylates Tomato Transcription Factor SlERF4 to Suppress Ethylene Responses and Promote Pathogen Growth

Cell Host and Microbe - Xanthomonas Type III Effector XopD Desumoylates Tomato Transcription Factor SlERF4 to Suppress Ethylene Responses and Promote Pathogen Growth | tomato | Scoop.it

XopD, a type III secretion effector from Xanthomonas euvesicatoria (Xcv), the causal agent of bacterial spot of tomato, is required for pathogen growth and delay of host symptom development. XopD carries a C-terminal SUMO protease domain, a host range determining nonspecific DNA-binding domain and two EAR motifs typically found in repressors of stress-induced transcription. The precise target(s) and mechanism(s) of XopD are obscure. We report that XopD directly targets the tomato ethylene responsive transcription factor SlERF4 to suppress ethylene production, which is required for anti-Xcv immunity and symptom development. SlERF4 expression was required for Xcv ΔxopD-induced ethylene production and ethylene-stimulated immunity. XopD colocalized with SlERF4 in subnuclear foci and catalyzed SUMO1 hydrolysis from lysine 53 of SlERF4, causing SlERF4 destabilization. Mutation of lysine 53 prevented SlERF4 sumoylation, decreased SlERF4 levels, and reduced SlERF4 transcription. These data suggest that XopD desumoylates SlERF4 to repress ethylene-induced transcription required for anti-Xcv immunity.


Via Suayib Üstün, CP
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Rescooped by tianxing84 from Plants and Microbes
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PLOS Pathogens: Coevolution and Hierarchical Interactions of Tomato mosaic virus and the Resistance Gene Tm-1 (2012)

PLOS Pathogens: Coevolution and Hierarchical Interactions of Tomato mosaic virus and the Resistance Gene Tm-1 (2012) | tomato | Scoop.it

During antagonistic coevolution between viruses and their hosts, viruses have a major advantage by evolving more rapidly. Nevertheless, viruses and their hosts coexist and have coevolved, although the processes remain largely unknown. We previously identified Tm-1 that confers resistance to Tomato mosaic virus (ToMV), and revealed that it encodes a protein that binds ToMV replication proteins and inhibits RNA replication. Tm-1 was introgressed from a wild tomato species Solanum habrochaites into the cultivated tomato species Solanum lycopersicum. In this study, we analyzed Tm-1 alleles in S. habrochaites. Although most part of this gene was under purifying selection, a cluster of nonsynonymous substitutions in a small region important for inhibitory activity was identified, suggesting that the region is under positive selection. We then examined the resistance of S. habrochaites plants to ToMV. Approximately 60% of 149 individuals from 24 accessions were resistant to ToMV, while the others accumulated detectable levels of coat protein after inoculation. Unexpectedly, many S. habrochaites plants were observed in which even multiplication of the Tm-1-resistance-breaking ToMV mutant LT1 was inhibited. An amino acid change in the positively selected region of the Tm-1 protein was responsible for the inhibition of LT1 multiplication. This amino acid change allowed Tm-1 to bind LT1 replication proteins without losing the ability to bind replication proteins of wild-type ToMV. The antiviral spectra and biochemical properties suggest that Tm-1 has evolved by changing the strengths of its inhibitory activity rather than diversifying the recognition spectra. In the LT1-resistant S. habrochaites plants inoculated with LT1, mutant viruses emerged whose multiplication was not inhibited by the Tm-1 allele that confers resistance to LT1. However, the resistance-breaking mutants were less competitive than the parental strains in the absence of Tm-1. Based on these results, we discuss possible coevolutionary processes of ToMV and Tm-1.


Via Kamoun Lab @ TSL
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Rescooped by tianxing84 from Plants&Bacteria
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The In Planta Transcriptome of Ralstonia solanacearum: Conserved Physiological and Virulence Strategies during Bacterial Wilt of Tomato, by Jacobs et al., in mBIO

The In Planta Transcriptome of Ralstonia solanacearum: Conserved Physiological and Virulence Strategies during Bacterial Wilt of Tomato, by Jacobs et al., in mBIO | tomato | Scoop.it

This paper confirms our findings of late expression of T3SS genes at late stages of disease development in planta, reported previously in Microbiology http://mic.sgmjournals.org/content/early/2012/05/15/mic.0.058610-0.abstract

As a friend said before: "It feels so good to have your results confirmed by an independent group, using a different approach".

 

This publication also explores the metabolic adaptations of R. solanacearum during colonization and multiplication in planta, focusing on the particular case of sucrose uptake and catabolism.

 

Summary:

Although much is known about the signals that trigger transcription of virulence genes in plant pathogens, their prevalence and timing during infection are still unknown. In this work, we address these questions by analysing expression of the main pathogenicity determinants in the bacterial pathogen R. solanacearum. We set up a quantitative, non-invasive luminescent reporter to monitor in planta transcription from single promoters in the bacterial chromosome. We show that the new reporter provides a real-time measure of promoter output in vivo -either after re-isolation of pathogens from infected plants or directly in situ- and confirm that the promoter controlling exopolysaccharide synthesis is active in bacteria growing in the xylem. We also provide evidence that hrpB -the master regulator of type III secretion system genes- is transcribed in symptomatic plants. Quantitative RT-PCR assays demonstrate that hrpB and type III effector transcripts are abundant at late stages of plant infection suggesting that their function is required throughout disease. Our results challenge the widespread view in R. solanacearum pathogenicity that the type III secretion system - and thus injection of effector proteins- is only active to manipulate plant defences at the first stages of infection, and that their expression is turned down when bacteria reach high cell densities and exopolysaccharide synthesis starts.


Via Freddy Monteiro
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Rescooped by tianxing84 from Plant-microbe interaction
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The tomato genome sequence provides insights into fleshy fruit evolution : Nature : Nature Publishing Group

The tomato genome sequence provides insights into fleshy fruit evolution : Nature : Nature Publishing Group | tomato | Scoop.it

Tomato (Solanum lycopersicum) is a major crop plant and a model system for fruit development. Solanum is one of the largest angiosperm genera and includes annual and perennial plants from diverse habitats. Here we present a high-quality genome sequence of domesticated tomato, a draft sequence of its closest wild relative, Solanumpimpinellifolium, and compare them to each other and to the potato genome (Solanum tuberosum). The two tomato genomes show only 0.6% nucleotide divergence and signs of recent admixture, but show more than 8% divergence from potato, with nine large and several smaller inversions. In contrast to Arabidopsis, but similar to soybean, tomato and potato small RNAs map predominantly to gene-rich chromosomal regions, including gene promoters. The Solanum lineage has experienced two consecutive genome triplications: one that is ancient and shared with rosids, and a more recent one. These triplications set the stage for the neofunctionalization of genes controlling fruit characteristics, such as colour and fleshiness.


Via Suayib Üstün
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Rescooped by tianxing84 from Plant Genomics
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Fungal Small RNAs Suppress Plant Immunity by Hijacking Host RNA Interference Pathways


Via Biswapriya Biswavas Misra
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Biswapriya Biswavas Misra's curator insight, October 4, 2013 2:04 PM

Botrytis cinerea, the causative agent of gray mold disease, is an aggressive fungal pathogen that infects more than 200 plant species. Here, we show that some B. cinerea small RNAs (Bc-sRNAs) can silence Arabidopsis and tomato genes involved in immunity. These Bc-sRNAs hijack the host RNA interference (RNAi) machinery by binding to Arabidopsis Argonaute 1 (AGO1) and selectively silencing host immunity genes. The Arabidopsis ago1 mutant exhibits reduced susceptibility to B. cinerea, and the B. cinerea dcl1 dcl2 double mutant that can no longer produce these Bc-sRNAs displays reduced pathogenicity on Arabidopsis and tomato. Thus, this fungal pathogen transfers “virulent” sRNA effectors into host plant cells to suppress host immunity and achieve infection, which demonstrates a naturally occurring cross-kingdom RNAi as an advanced virulence mechanism.

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Transcriptional repression of BODENLOS by HD-ZIP transcription factor HB5 in Arabidopsis thaliana

Transcriptional repression of BODENLOS by HD-ZIP transcription factor HB5 in Arabidopsis thaliana | tomato | Scoop.it

Via PMG
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PMG's curator insight, July 2, 2013 8:04 PM

WRKY6:CKX1 plants exhibited high CKX activity in the roots under control conditions. Under stress, the activity of the WRKY6 promoter was down-regulated and the concomitantly reduced cytokinin degradation coincided with raised bioactive cytokinin levels during the early phase of the stress response, which might contribute to enhanced stress tolerance of this genotype. Constitutive expression of CKX1 resulted in an enlarged root system, a stunted, dwarf shoot phenotype, and a low basal level of expression of the dehydration marker gene ERD10B. The high drought tolerance of this genotype was associated with a relatively moderate drop in leaf water potential and a significant decrease in leaf osmotic potential. Basal expression of the proline biosynthetic gene P5CSA was raised. Both wild-type and WRKY6:CKX1 plants responded to heat stress by transient elevation of stomatal conductance, which correlated with an enhanced abscisic acid catabolism. 35S:CKX1 transgenic plants exhibited a small and delayed stomatal response. Nevertheless, they maintained a lower leaf temperature than the other genotypes. Heat shock applied to drought-stressed plants exaggerated the negative stress effects, probably due to the additional water loss caused by a transient stimulation of transpiration. The results indicate that modulation of cytokinin levels may positively affect plant responses to abiotic stress through a variety of physiological mechanisms.

Rescooped by tianxing84 from Plant Genomics
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The developing xylem transcriptome and genome-wide analysis of alternative splicing in Populus trichocarpa (black cottonwood) populations

Alternative splicing (AS) of genes is an efficient means of generating variation in protein structure and function.

Via Biswapriya Biswavas Misra
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Biswapriya Biswavas Misra's curator insight, May 30, 2013 1:21 PM
Abstract (provisional)Background

Alternative splicing (AS) of genes is an efficient means of generating variation in protein structure and function. AS variation has been observed between tissues, cell types, and different treatments in non-woody plants such as Arabidopsis thaliana (Arabidopsis) and rice. However, little is known about AS patterns in wood-forming tissues and how much AS variation exists within plant populations.

Results

Here we used high-throughput RNA sequencing to analyze the Populus trichocarpa (P. trichocarpa) xylem transcriptome in 20 individuals from different populations across much of its range in western North America. Deep transcriptome sequencing and mapping of reads to the P. trichocarpa reference genome identified a suite of xylem-expressed genes common to all accessions. Our analysis suggests that at least 36% of the xylem-expressed genes in P. trichocarpa are alternatively spliced. Extensive AS was observed in cell-wall biosynthesis related genes such as glycosyl transferases and C2H2 transcription factors. 27902 AS events were documented and most of these events were not conserved across individuals. Differences in isoform-specific read densities indicated that 7% and 13% of AS events showed significant differences between individuals within geographically separated southern and northern populations, a level that is in general agreement with AS variation in human populations.

Conclusions

This genome-wide analysis of alternative splicing reveals high levels of AS in P. trichocarpa and extensive inter-individual AS variation. We provide the most comprehensive analysis of AS in P. trichocarpa to date, which will serve as a valuable resource for the plant community to study transcriptome complexity and AS regulation during wood formation.

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Adenine Phosphoribosyl Transferase 1 is a Key Enzyme Catalyzing Cytokinin Conversion from Nucleobases to Nucleotides in Arabidopsis

Adenine Phosphoribosyl Transferase 1 is a Key Enzyme Catalyzing Cytokinin Conversion from Nucleobases to Nucleotides in Arabidopsis | tomato | Scoop.it

Via PMG
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PMG's curator insight, May 14, 2013 5:21 PM

APT1 catalyzes the cytokinin conversion from free bases to nucleotides, and is functionally predominant among the five members of the Arabidopsis Adenine Phosphoribosyl Transferase family. Loss of APT1 activity in plants leads to excess accumulation of cytokinin bases, thus evoking myriad cytokinin-regulated responses, such as delayed leaf senescence, anthocyanin accumulation, and downstream gene expression. Thus, our study defines APT1 as a key metabolic enzyme participating in the cytokinin inactivation by phosphoribosylation.

Rescooped by tianxing84 from Plant Pathogenomics
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eLife: The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine (2013)

eLife: The rise and fall of the Phytophthora infestans lineage that triggered the Irish potato famine (2013) | tomato | Scoop.it

Phytophthora infestans, the cause of potato late blight, is infamous for having triggered the Irish Great Famine in the 1840s. Until the late 1970s, P. infestans diversity outside of its Mexican center of origin was low, and one scenario held that a single strain, US-1, had dominated the global population for 150 years; this was later challenged based on DNA analysis of historical herbarium specimens. We have compared the genomes of 11 herbarium and 15 modern strains. We conclude that the nineteenth century epidemic was caused by a unique genotype, HERB-1, that persisted for over 50 years. HERB-1 is distinct from all examined modern strains, but it is a close relative of US-1, which replaced it outside of Mexico in the twentieth century. We propose that HERB-1 and US-1 emerged from a metapopulation that was established in the early 1800s outside of the species' center of diversity.

 

Preprint @ http://arxiv.org/abs/1305.4206


Via Kamoun Lab @ TSL
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Alejandro Rojas's curator insight, May 21, 2013 4:54 AM

I'm so excited to see a paper like this!, It is so great to have acces to papers like this through systems like ArXiv.  

Jennifer Mach's comment, May 21, 2013 6:34 AM
Nature News and Views article: http://www.nature.com/news/pathogen-genome-tracks-irish-potato-famine-back-to-its-roots-1.13021
Mary Williams's comment, May 21, 2013 8:45 AM
On the radio http://kamounlab.tumblr.com/post/50992192578/go-back-to-the-past-to-better-prepare-for-the
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PLOS ONE: Graft Transmission of RNA Silencing to Non-Transgenic Scions for Conferring Virus Resistance in Tobacco

PLOS ONE: Graft Transmission of RNA Silencing to Non-Transgenic Scions for Conferring Virus Resistance in Tobacco | tomato | Scoop.it

RNA silencing is a mechanism of gene regulation by sequence specific RNA degradation and is involved in controlling endogenous gene expression and defense against invasive nucleic acids such as viruses. RNA silencing has been proven to be transmitted between scions and rootstocks through grafting, mostly using transgenic plants. It has been reported that RNA silencing of tobacco endogenous genes, NtTOM1 and NtTOM3, that are required for tobamovirus multiplication, resulted in high resistance against several tobamoviruses. In the present study, we examined the graft transmission of RNA silencing for conferring virus resistance to non-transgenic scions of the same and different Nicotiana species grafted onto rootstocks in which both NtTOM1 and NtTOM3 were silenced. Non-transgenic Nicotiana tabacum (cvs. Samsun and Xanthi nc) and N. benthamiana were used as scions for grafting onto the rootstocks silenced with both genes. Short interfering RNA (siRNA) of NtTOM1 andNtTOM3 was detected in both the scions and the rootstocks eight weeks after grafting. The leaves were detached from the scions and inoculated with several tobamoviruses. The virus accumulation was tested by ELISA and northern blot analysis. The viruses were detected in grafted scions at extremely low levels, showing that virus resistance was conferred. These results suggest that RNA silencing was induced in and virus resistance was conferred to the non-transgenic scions by grafting onto silenced rootstocks. The effect of low temperature on siRNA accumulation and virus resistance was not significantly observed in the scions.

  

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Multiple forms of vector manipulation by a plant-infecting virus: Bemisia tabaci and tomato yellow leaf curl virus

Multiple forms of vector manipulation by a plant-infecting virus: Bemisia tabaci and tomato yellow leaf curl virus | tomato | Scoop.it

For many insect-vectored plant viruses, the relationship between feeding behavior and vector competence may prove integral to understanding the epidemiology of the resulting plant disease. While plant-infecting viruses are well known to change host plant physiology in a way that makes them more attractive to vectors, viral manipulation of the vectors themselves has only recently been reported. Previous research has suggested that the rapid spread of tomato yellow leaf curl virus (TYLCV) throughout China has been facilitated by its primary vector, the whitefly Bemisia tabaci. We conducted two experiments testing the impact of TYLCV infection of the host plant (tomato) and vector (B. tabaci biotypes B and Q) on whitefly feeding behavior. Biotypes B and Q both appeared to find TYLCV-infected plants more attractive, probing them more quickly and having a greater number of feeding bouts; this did not, however, alter the total time spent feeding. Viruliferous whiteflies fed more readily than uninfected whiteflies, and spent more time salivating into sieve tube elements. Because vector salivation is essential for viral transmission, this virally-mediated alteration of behavior should provide TYLCV a direct fitness benefit. This is the first report of such manipulation by a nonpropagative virus that belongs to an exclusively plant-infecting family of viruses (Geminiviridae). In the context of previous research showing that feeding on TYLCV-infected plants harms biotype B but helps biotype Q, the fact that both biotypes were equally affected by TYLCV also suggests that the virus may alter the B-Q competitive interaction in favor of biotype Q.

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Deciphering the route of R. solanacearum colonization in A. thaliana roots during a compatible interaction: focus at the plant cell wall, by Catherine Digonnet and collaborators, in Planta

Deciphering the route of R. solanacearum colonization in A. thaliana roots during a compatible interaction: focus at the plant cell wall, by Catherine Digonnet and collaborators, in Planta | tomato | Scoop.it

Although Arabidopsis has never been a natural host for Ralstonia solanacearum, and although no economical implications arise from the Arabidopsis-Ralstonia interaction, the use of this model plant have proven critical in the undertanding of disease progress and the role of specific effector genes as PopP2. So much for the criticism ever received, here we are presented with a nice colonization walkthrough document, only made possible when the expertise from groups like Deborah Goffner's and Yves Marco's are put together in a joint effort.

 

Summary:

The compatible interaction between the model plant, Arabidopsis thaliana, and the GMI1000 strain of the phytopathogenic bacterium, Ralstonia solanacearum, was investigated in an in vitro pathosystem. We describe the progression of the bacteria in the root from penetration at the root surface to the xylem vessels and the cell type specific, cell wall-associated modifications that accompanies bacterial colonization. Within 6 days post inoculation, R. solanacearum provoked a rapid plasmolysis of the epidermal, cortical, and endodermal cells, including those not directly in contact with the bacteria. Plasmolysis was accompanied by a global degradation of pectic homogalacturonanes as shown by the loss of JIM7 and JIM5 antibody signal in the cell wall of these cell types. As indicated by immunolabeling with Rsol-I antibodies that specifically recognize R. solanacearum, the bacteria progresses through the root in a highly directed, centripetal manner to the xylem poles, without extensive  multiplication in the intercellular spaces along its path. Entry into the vascular cylinder was facilitated by cell collapse of the two pericycle cells located at the xylem poles. Once the bacteria reached the xylem vessels, they multiplied abundantly and moved from vessel to vessel by digesting the pit membrane between adjacent vessels. The degradation of the secondary walls of xylem vessels was not a prerequisite for vessel colonization as LM10 antibodies strongly labeled xylem cell walls, even at very late stages in disease development. Finally, the capacity of R. solanacearum to specifically degrade certain cell wall components and not others could be correlated with the arsenal of cell wall hydrolytic enzymes identified in the bacterial genome.


Via Freddy Monteiro
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Do Plants Think? Scientist Gives Surprising Answer

Do Plants Think? Scientist Gives Surprising Answer | tomato | Scoop.it

How aware are plants? This is the central question behind a fascinating new book, “What a plant knows” by Daniel Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University. A plant, he argues, can see, smell and feel. It can mount a defense when under siege, and warn its neighbors of trouble on the way. A plant can even be said to have a memory. But does this mean that plants think — or that one can speak of a “neuroscience” of the flower? Chamovitz answered questions from Mind Matters editor Gareth Cook.


Via Suayib Üstün
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