Emerging Research...
Follow
Find
12.9K views | +1 today
 
Rescooped by Jennifer Mach from Plant Biology Teaching Resources (Higher Education)
onto Emerging Research in Plant Cell Biology
Scoop.it!

Plant Cell Environ: Salt Glands in mangrove

Plant Cell Environ: Salt Glands in mangrove | Emerging Research in Plant Cell Biology | Scoop.it

Salt glands are fascinating anatomically and physiologically. If you've never read the great SCHMIDT-NIELSEN's work, here's a link to an OA paper on "The salt-secreting glands of marine birds", from 1960. (http://circ.ahajournals.org/content/21/5/955.abstract).

 

Salt glands seem to be an example of convergent evolution. They've arisen repeatedly to deal with the problem salt elimination without too much water loss. They are a terrific tool to help students learn about the movement of ions across membranes. 

 

Here are a few review articles with more information about salt glands and other halophyte adaptations:

Flowers and Colmer, New Phytol 2008 (http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2008.02531.x/full)

Munns and Tester, Annu Rev Plant Biol 2008 (http://www.annualreviews.org/doi/abs/10.1146/annurev.arplant.59.032607.092911?journalCode=arplant)

Flowers et al, Functional Plant Biol. 2010 (http://www.tempoandmode.com/wp-content/uploads/2010/07/flowersevolutionhalophytesfuncplbiol10.pdf)and from

Plants in Action (http://plantsinaction.science.uq.edu.au/edition1/?q=content/17-3-1-devices-manage-leaf-salt).


Via Mary Williams
more...
No comment yet.

From around the web

Emerging Research in Plant Cell Biology
A science editor's take on what's new and interesting in the plant kingdom.
Curated by Jennifer Mach
Your new post is loading...
Your new post is loading...
Rescooped by Jennifer Mach from Effectors and Plant Immunity
Scoop.it!

The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling

The inter-kingdom volatile signal indole promotes root development by interfering with auxin signalling | Emerging Research in Plant Cell Biology | Scoop.it
Recently, emission of volatile organic compounds (VOCs) has emerged as a mode of communication between bacteria and plants. Although some bacterial VOCs that promote plant growth have been identified, their underlying mechanism of action is unknown. Here we demonstrate that indole, which was identified using a screen for Arabidopsis growth promotion by VOCs from soil-borne bacteria, is a potent plant-growth modulator. Its prominent role in increasing the plant secondary root network is mediated by interfering with the auxin-signalling machinery. Using auxin reporter lines and classic auxin physiological and transport assays we show that the indole signal invades the plant body, reaches zones of auxin activity and acts in a polar auxin transport-dependent bimodal mechanism to trigger differential cellular auxin responses. Our results suggest that indole, beyond its importance as a bacterial signal molecule, can serve as a remote messenger to manipulate plant growth and development.

Via Francis Martin, Nicolas Denancé
more...
No comment yet.
Rescooped by Jennifer Mach from Plant roots and rhizosphere
Scoop.it!

The CLE40 and CRN/CLV2 Signaling Pathways Antagonistically Control Root Meristem Growth in Arabidopsis

The CLE40 and CRN/CLV2 Signaling Pathways Antagonistically Control Root Meristem Growth in Arabidopsis | Emerging Research in Plant Cell Biology | Scoop.it
Differentiation processes in the primary root meristem are controlled by several signaling pathways that are regulated by phytohormones or by secreted peptides. Long-term maintenance of an active root meristem requires that the generation of new stem cells and the loss of these from the meristem due to differentiation are precisely coordinated. Via phenotypic and large-scale transcriptome analyses of mutants, we show that the signaling peptide CLE40 and the receptor proteins CLV2 and CRN act in two genetically separable pathways that antagonistically regulate cell differentiation in the proximal root meristem. CLE40 inhibits cell differentiation throughout the primary root meristem by controlling genes with roles in abscisic acid, auxin, and cytokinin signaling. CRN and CLV2 jointly control target genes that promote cell differentiation specifically in the transition zone of the proximal root meristem. While CRN and CLV2 are not acting in the CLE40 signaling pathway under normal growth conditions, both proteins are required when the levels of CLE40 or related CLE peptides increase. We show here that two antagonistically acting pathways controlling root meristem differentiation can be activated by the same peptide in a dosage-dependent manner.

Via Christophe Jacquet
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Species-wide Genetic Incompatibility Analysis Identifies Immune Genes as Hot Spots of Deleterious Epistasis: Cell

Species-wide Genetic Incompatibility Analysis Identifies Immune Genes as Hot Spots of Deleterious Epistasis: Cell | Emerging Research in Plant Cell Biology | Scoop.it

Intraspecific genetic incompatibilities prevent the assembly of specific alleles into single genotypes and influence genome- and species-wide patterns of sequence variation. A common incompatibility in plants is hybrid necrosis, characterized by autoimmune responses due to epistatic interactions between natural genetic variants. By systematically testing thousands of F1 hybrids of Arabidopsis thalianastrains, we identified a small number of incompatibility hot spots in the genome, often in regions densely populated by nucleotide-binding domain and leucine-rich repeat (NLR) immune receptor genes. In several cases, these immune receptor loci interact with each other, suggestive of conflict within the immune system. A particularly dangerous locus is a highly variable cluster of NLR genes, DM2, which causes multiple independent incompatibilities with genes that encode a range of biochemical functions, including NLRs. Our findings suggest that deleterious interactions of immune receptors limit the combinations of favorable disease resistance alleles accessible to plant genomes.

more...
No comment yet.
Rescooped by Jennifer Mach from MycorWeb Plant-Microbe Interactions
Scoop.it!

Interspecific and host-related gene expression patterns in nematode-trapping fungi

Interspecific and host-related gene expression patterns in nematode-trapping fungi | Emerging Research in Plant Cell Biology | Scoop.it

Background

Nematode-trapping fungi are soil-living fungi that capture and kill nematodes using special hyphal structures called traps. They display a large diversity of trapping mechanisms and differ in host preferences. To provide insights into the genetic basis for this variation, we compared the transcriptome expressed by three species of nematode-trapping fungi during the infection of two different plant-pathogenic nematode hosts, the root knot nematode Meloidogyne hapla and the sugar beet cyst nematode Heterodera schachtii. The fungi were forming either adhesive nets, adhesive branches or constricting rings as trapping structures.

Results

The analyses showed that the divergence in gene expression between the fungi was significantly larger than that related to the nematode species. Transcripts predicted to encode secreted proteins and proteins with unknown function (i.e. orphans) were overrepresented among the highly expressed transcripts in all fungi. Highly expressed in all fungi were genes encoding endopeptidases such as subtilisins and aspartic proteases, cell-surface proteins containing the carbohydrate-binding domain WSC, stress response proteins, membrane transporters, transcription factors, and transcripts containing the Ricin-B lectin domain. Differentially expressed transcripts among the fungal species were those encoding various lectins such as the fungal fruit-body lectin and the D-mannose binding lectin, transcription factors, cell signaling components and proteins with the WSC domain and the DUF3129 domain. A small set of transcripts was significantly regulated depending on the host nematode. They included peptidases, WSC domain proteins, tyrosinases, and small secreted proteins (SSPs) with unknown function.

Conclusions

This is the first study on the variation of infection-related gene expression patterns in nematode-trapping fungi infecting different host species. A better understanding of these patterns will facilitate the improvements of these fungi in biological control programs, by providing molecular markers for screening programs and candidates for genetic manipulations of virulence and host preferences.


Via Christophe Jacquet, Francis Martin
more...
No comment yet.
Rescooped by Jennifer Mach from Plant-microbe interaction
Scoop.it!

Curr Opin Microbiology: Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors (2014)

Curr Opin Microbiology: Targeting of plant pattern recognition receptor-triggered immunity by bacterial type-III secretion system effectors (2014) | Emerging Research in Plant Cell Biology | Scoop.it

• Type-III effectors (T3Es) suppress plant immunity using multiple strategies.
• PRR-triggered immunity is redundantly targeted by multiple T3Es from a single bacterial strain.
• A single T3E can have multiple plant targets.
• A given immune component can be targeted by multiple T3Es.
• The study of T3Es reveals important immune components and unique biochemical processes.

 

During infection, microbes are detected by surface-localized pattern recognition receptors (PRRs), leading to an innate immune response that prevents microbial ingress. Therefore, successful pathogens must evade or inhibit PRR-triggered immunity to cause disease. In the past decade, a number of type-III secretion system effector (T3Es) proteins from plant pathogenic bacteria have been shown to suppress this layer of innate immunity. More recently, the detailed mechanisms of action have been defined for several of these effectors. Interestingly, effectors display a wide array of virulence targets, being able to prevent activation of immune receptors and to hijack immune signaling pathways. Besides being a fascinating example of pathogen-host co-evolution, effectors have also emerged as valuable tools to dissect important biological processes in host cells.


Via Kamoun Lab @ TSL, Suayib Üstün
more...
Scooped by Jennifer Mach
Scoop.it!

Evolution of DNA Methylation Patterns in the Brassicaceae is Driven by Differences in Genome Organization

Evolution of DNA Methylation Patterns in the Brassicaceae is Driven by Differences in Genome Organization | Emerging Research in Plant Cell Biology | Scoop.it
DNA methylation is an ancient molecular modification found in most eukaryotes. In plants, DNA methylation is not only critical for transcriptionally silencing transposons, but can also affect phenotype by altering expression of protein coding genes. The extent of its contribution to phenotypic diversity over evolutionary time is, however, unclear, because of limited stability of epialleles that are not linked to DNA mutations. To dissect the relative contribution of DNA methylation to transposon surveillance and host gene regulation, we leveraged information from three species in the Brassicaceae that vary in genome architecture, Capsella rubella,Arabidopsis lyrata, and Arabidopsis thaliana. We found that the lineage-specific expansion and contraction of transposon and repeat sequences is the main driver of interspecific differences in DNA methylation. The most heavily methylated portions of the genome are thus not conserved at the sequence level. Outside of repeat-associated methylation, there is a surprising degree of conservation in methylation at single nucleotides located in gene bodies. Finally, dynamic DNA methylation is affected more by tissue type than by environmental differences in all species, but these responses are not conserved. The majority of DNA methylation variation between species resides in hypervariable genomic regions, and thus, in the context of macroevolution, is of limited phenotypic consequence.
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

The AAA-ATPase molecular chaperone Cdc48/p97 disassembles sumoylated centromeres, decondenses heterochromatin, and activates ribosomal RNA genes

The AAA-ATPase molecular chaperone Cdc48/p97 disassembles sumoylated centromeres, decondenses heterochromatin, and activates ribosomal RNA genes | Emerging Research in Plant Cell Biology | Scoop.it

Centromeres mediate chromosome segregation and are defined by the centromere-specific histone H3 variant (CenH3)/centromere protein A (CENP-A). Removal of CenH3 from centromeres is a general property of terminally differentiated cells, and the persistence of CenH3 increases the risk of diseases such as cancer. However, active mechanisms of centromere disassembly are unknown. Nondividing Arabidopsis pollen vegetative cells, which transport engulfed sperm by extended tip growth, undergo loss of CenH3; centromeric heterochromatin decondensation; and bulk activation of silent rRNA genes, accompanied by their translocation into the nucleolus. Here, we show that these processes are blocked by mutations in the evolutionarily conserved AAA-ATPase molecular chaperone, CDC48A, homologous to yeast Cdc48 and human p97 proteins, both of which are implicated in ubiquitin/small ubiquitin-like modifier (SUMO)-targeted protein degradation. We demonstrate that CDC48A physically associates with its heterodimeric cofactor UFD1-NPL4, known to bind ubiquitin and SUMO, as well as with SUMO1-modified CenH3 and mutations inNPL4 phenocopy cdc48a mutations. In WT vegetative cell nuclei, genetically unlinked ribosomal DNA (rDNA) loci are uniquely clustered together within the nucleolus and all major rRNA gene variants, including those rDNA variants silenced in leaves, are transcribed. In cdc48a mutant vegetative cell nuclei, however, these rDNA loci frequently colocalized with condensed centromeric heterochromatin at the external periphery of the nucleolus. Our results indicate that the CDC48ANPL4 complex actively removes sumoylated CenH3 from centromeres and disrupts centromeric heterochromatin to release bulk rRNA genes into the nucleolus for ribosome production, which fuels single nucleus-driven pollen tube growth and is essential for plant reproduction.

more...
No comment yet.
Rescooped by Jennifer Mach from Effectors and Plant Immunity
Scoop.it!

MPMI: Functional analysis of plant defense suppression and activation by the Xanthomonas core type III effector XopX

MPMI: Functional analysis of plant defense suppression and activation by the Xanthomonas core type III effector XopX | Emerging Research in Plant Cell Biology | Scoop.it

Many phytopathogenic type III secretion effectors (T3Es) have been shown to target and suppress plant immune signaling, but perturbation of the plant immune system by T3Es can also elicit a plant response. XopX is a “core” Xanthomonas T3E that contributes to growth and symptom development during Xanthomonas euvesicatoria (Xe) infection of tomato, but its functional role is undefined. We tested the effect of XopX on several aspects of plant immune signaling. XopX promoted ethylene production and plant cell death (PCD) during Xe infection of susceptible tomato and in transient expression assays in Nicotiana benthamiana, which is consistent with its requirement for the development of Xe-induced disease symptoms. Additionally, although XopX suppressed flagellin-induced reactive oxygen species, it promoted the accumulation of pattern-triggered immunity (PTI) gene transcripts. Surprisingly, XopX co-expression with other PCD elicitors resulted in delayed PCD, suggesting antagonism between XopX-dependent PCD and other PCD pathways. However, we found no evidence that XopX contributed to the suppression of effector-triggered immunity during Xe-tomato interactions, suggesting that XopX’s primary virulence role is to modulate PTI. These results highlight the dual role of a core Xanthomonas T3E in simultaneously suppressing and activating plant defense responses.


Via Jim Alfano, Nicolas Denancé
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

ULTRAPETALA trxG Genes Interact with KANADI Transcription Factor Genes to Regulate Arabidopsis Gynoecium Patterning

ULTRAPETALA trxG Genes Interact with KANADI Transcription Factor Genes to Regulate Arabidopsis Gynoecium Patterning | Emerging Research in Plant Cell Biology | Scoop.it

Organ formation relies upon precise patterns of gene expression that are under tight spatial and temporal regulation. Transcription patterns are specified by several cellular processes during development, including chromatin remodeling, but little is known about how chromatin-remodeling factors contribute to plant organogenesis. We demonstrate that the trithorax group (trxG) geneULTRAPETALA1 (ULT1) and the GARP transcription factor gene KANADI1 (KAN1) organize the Arabidopsis thaliana gynoecium along two distinct polarity axes. We show that ULT1 activity is required for the kan1 adaxialized polarity defect, indicating that ULT1 and KAN1 act oppositely to regulate the adaxial-abaxial axis. Conversely, ULT1 and KAN1 together establish apical-basal polarity by promoting basal cell fate in the gynoecium, restricting the expression domain of the basic helix-loop-helix transcription factor gene SPATULA. Finally, we show that ultalleles display dose-dependent genetic interactions with kan alleles and that ULT and KAN proteins can associate physically. Our findings identify a dual role for plant trxG factors in organ patterning, with ULT1 and KAN1 acting antagonistically to pattern the adaxial-abaxial polarity axis but jointly to pattern the apical-basal axis. Our data indicate that the ULT proteins function to link chromatin-remodeling factors with DNA binding transcription factors to regulate target gene expression.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Evolutionary divergence of β-expansin structure and function in grasses parallels emergence of distinctive primary cell wall traits

Evolutionary divergence of β-expansin structure and function in grasses parallels emergence of distinctive primary cell wall traits | Emerging Research in Plant Cell Biology | Scoop.it

Expansins are wall-loosening proteins that promote extension of primary cell walls without hydrolysis of major structural components. Previously, proteins from the EXPA (α-expansin) family were found to loosen eudicot cell walls but to be less effective on grass cell walls, whereas the reverse pattern was found for EXPB (β-expansin) proteins obtained from grass pollen. To understand the evolutionary and structural bases for the selectivity of EXPB action, we assessed the extension (creep) response of cell walls from diverse monocot families to EXPA and EXPB treatments. Cell walls from Cyperaceae and Juncaceae (families closely related to grasses) displayed a typical grass response (“β-response”). Walls from more distant monocots, including some species that share with grasses high levels of arabinoxylan, responded preferentially to α-expansins (“α-response”), behaving in this regard like eudicots. An expansin with selective activity for grass cell walls was detected in Cyperaceae pollen, coinciding with the expression of genes from the divergent EXPB-I branch that includes grass pollen β-expansins. The evolutionary origin of this branch was located within Poales on the basis of phylogenetic analyses and its association with the “sigma” whole genome duplication. Accelerated evolution in this branch has remodeled the protein surface in contact with the substrate, potentially for binding highly substituted arabinoxylan. We propose that the evolution of the divergent EXPB-I group made possible a fundamental change in the target and mechanism of wall loosening in the grass lineage, involving a new structural role for xylans and the expansins that target them.

more...
No comment yet.
Rescooped by Jennifer Mach from Plant Biology Teaching Resources (Higher Education)
Scoop.it!

Increasing complexity and versatility: How the calcium signaling toolkit was shaped during plant land colonization

Calcium serves as a versatile messenger in adaptation reactions and developmental processes in plants and animals. Eukaryotic cells generate cytosolic Ca2+ signals via Ca2+-conducting channels. Ca2+ signals are represented in form of stimulus-specific spatially and temporally defined Ca2+ signatures. These Ca2+ signatures are detected, decoded and transmitted to downstream responses by an elaborate toolkit of Ca2+ binding proteins that function as Ca2+ sensors.

In this article, we examine the distribution and evolution of Ca2+-conducting channels and Ca2+ decoding proteins in the plant lineage. To this end, we have in addition to previously studied genomes of plant species, identified and analyzed the Ca2+-signaling components from species that hold key evolutionary positions like the filamentous terrestrial algae Klebsormidium flaccidum and Amborella trichopoda, the single living representative of the sister lineage to all other extant flowering plants.

Plants and animals exhibit substantial differences in their complements of Ca2+ channels and Ca2+ binding proteins. Within the plant lineage, remarkably differences in the evolution of complexity between different families of Ca2+ signaling proteins are observable. Using the CBL/CIPK Ca2+ sensor/kinase signaling network as model, we attempt to link evolutionary tendencies to functional predictions. Our analyses, for example, suggests Ca2+ dependent regulation of Na+ homeostasis as an evolutionary most ancient function of this signaling network. Overall, gene families of Ca2+ signaling proteins have significantly increased in their size during plant evolution reaching an extraordinary complexity in Angiosperms.

Via Jean-Michel Ané, Pierre-Marc Delaux, Mary Williams
more...
Pierre-Marc Delaux's curator insight, November 9, 4:11 PM

Great paper ! CCaMK seems specific of land plants ! (really ? :p)

Rescooped by Jennifer Mach from Plant roots and rhizosphere
Scoop.it!

The life of phi: the development of phi thickenings in roots of the orchids of the genus Miltoniopsis

The life of phi: the development of phi thickenings in roots of the orchids of the genus Miltoniopsis | Emerging Research in Plant Cell Biology | Scoop.it

Phi thickenings, bands of secondary wall thickenings that reinforce the primary wall of root cortical cells in a wide range of species, are described for the first time in the epiphytic orchid Miltoniopsis. As with phi thickenings found in other plants, the phi thickenings in Miltoniopsis contain highly aligned cellulose running along the lengths of the thickenings, and are lignified but not suberized. Using a combination of histological and immunocytochemical techniques, thickening development can be categorized into three different stages. Microtubules align lengthwise along the thickening during early and intermediate stages of development, and callose is deposited within the thickening in a pattern similar to the microtubules. These developing thickenings also label with the fluorescently tagged lectin wheat germ agglutinin (WGA). These associations with microtubules and callose, and the WGA labeling, all disappear when the phi thickenings are mature. This pattern of callose and WGA deposition show changes in the thickened cell wall composition and may shed light on the function of phi thickenings in plant roots, a role for which has yet to be established.

 

 


Via Christophe Jacquet
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

The Role of cis Regulatory Evolution in Maize Domestication

The Role of cis Regulatory Evolution in Maize Domestication | Emerging Research in Plant Cell Biology | Scoop.it

Gene expression differences between divergent lineages caused by modification of cisregulatory elements are thought to be important in evolution. We assayed genome-wide cis andtrans regulatory differences between maize and its wild progenitor, teosinte, using deep RNA sequencing in F1 hybrid and parent inbred lines for three tissue types (ear, leaf and stem). Pervasive regulatory variation was observed with approximately 70% of ~17,000 genes showing evidence of regulatory divergence between maize and teosinte. However, many fewer genes (1,079 genes) show consistent cis differences with all sampled maize and teosinte lines. For ~70% of these 1,079 genes, the cis differences are specific to a single tissue. The number of genes with cis regulatory differences is greatest for ear tissue, which underwent a drastic transformation in form during domestication. As expected from the domestication bottleneck, maize possesses less cis regulatory variation than teosinte with this deficit greatest for genes showing maize-teosinte cis regulatory divergence, suggesting selection on cis regulatory differences during domestication. Consistent with selection on cis regulatory elements, genes with cis effects correlated strongly with genes under positive selection during maize domestication and improvement, while genes with trans regulatory effects did not. We observed a directional bias such that genes with cis differences showed higher expression of the maize allele more often than the teosinte allele, suggesting domestication favored up-regulation of gene expression. Finally, this work documents the cis and trans regulatory changes between maize and teosinte in over 17,000 genes for three tissues.

more...
No comment yet.
Rescooped by Jennifer Mach from Plant roots and rhizosphere
Scoop.it!

The CLE40 and CRN/CLV2 Signaling Pathways Antagonistically Control Root Meristem Growth in Arabidopsis

The CLE40 and CRN/CLV2 Signaling Pathways Antagonistically Control Root Meristem Growth in Arabidopsis | Emerging Research in Plant Cell Biology | Scoop.it
Differentiation processes in the primary root meristem are controlled by several signaling pathways that are regulated by phytohormones or by secreted peptides. Long-term maintenance of an active root meristem requires that the generation of new stem cells and the loss of these from the meristem due to differentiation are precisely coordinated. Via phenotypic and large-scale transcriptome analyses of mutants, we show that the signaling peptide CLE40 and the receptor proteins CLV2 and CRN act in two genetically separable pathways that antagonistically regulate cell differentiation in the proximal root meristem. CLE40 inhibits cell differentiation throughout the primary root meristem by controlling genes with roles in abscisic acid, auxin, and cytokinin signaling. CRN and CLV2 jointly control target genes that promote cell differentiation specifically in the transition zone of the proximal root meristem. While CRN and CLV2 are not acting in the CLE40 signaling pathway under normal growth conditions, both proteins are required when the levels of CLE40 or related CLE peptides increase. We show here that two antagonistically acting pathways controlling root meristem differentiation can be activated by the same peptide in a dosage-dependent manner.

Via Christophe Jacquet
more...
No comment yet.
Rescooped by Jennifer Mach from Plants and Microbes
Scoop.it!

Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014)

Cell Host & Microbe: The Calcium-Dependent Protein Kinase CPK28 Buffers Plant Immunity and Regulates BIK1 Turnover (2014) | Emerging Research in Plant Cell Biology | Scoop.it

• A forward-genetic screen identifies loci regulating Arabidopsis immune signaling
• MOB1/CPK28 negatively regulates immune signaling triggered by infection and PAMPs
• CPK28 interacts with and phosphorylates the central immune regulator BIK1
• CPK28 buffers immune responses and contributes to BIK1 turnover

 

Plant perception of pathogen-associated molecular patterns (PAMPs) triggers a phosphorylation relay leading to PAMP-triggered immunity (PTI). Despite increasing knowledge of PTI signaling, how immune homeostasis is maintained remains largely unknown. Here we describe a forward-genetic screen to identify loci involved in PTI and characterize the Arabidopsis calcium-dependent protein kinase CPK28 as a negative regulator of immune signaling. Genetic analyses demonstrate that CPK28 attenuates PAMP-triggered immune responses and antibacterial immunity. CPK28 interacts with and phosphorylates the plasma-membrane-associated cytoplasmic kinase BIK1, an important convergent substrate of multiple pattern recognition receptor (PRR) complexes. We find that BIK1 is rate limiting in PTI signaling and that it is continuously turned over to maintain cellular homeostasis. We further show that CPK28 contributes to BIK1 turnover. Our results suggest a negative regulatory mechanism that continually buffers immune signaling by controlling the turnover of this key signaling kinase.


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Asymmetric Epigenetic Modification and Elimination of rDNA Sequences by Polyploidization in Wheat

Asymmetric Epigenetic Modification and Elimination of rDNA Sequences by Polyploidization in Wheat | Emerging Research in Plant Cell Biology | Scoop.it

rRNA genes consist of long tandem repeats clustered on chromosomes, and their products are important functional components of the ribosome. In common wheat (Triticum aestivum), rDNA loci from the A and D genomes were largely lost during the evolutionary process. This biased DNA elimination may be related to asymmetric transcription and epigenetic modifications caused by the polyploid formation. Here, we observed both sets of parental nucleolus organizing regions (NORs) were expressed after hybridization, but asymmetric silencing of one parental NOR was immediately induced by chromosome doubling, and reversing the ploidy status could not reactivate silenced NORs. Furthermore, increased CHG and CHH DNA methylation on promoters was accompanied by asymmetric silencing of NORs. Enrichment of H3K27me3 and H3K9me2 modifications was also observed to be a direct response to increased DNA methylation and transcriptional inactivation of NOR loci. Both A and D genome NOR loci with these modifications started to disappear in the S4 generation and were completely eliminated by the S7 generation in synthetic tetraploid wheat. Our results indicated that asymmetric epigenetic modification and elimination of rDNA sequences between different donor genomes may lead to stable allopolyploid wheat with increased differentiation and diversity.

more...
No comment yet.
Rescooped by Jennifer Mach from Plant-microbe interaction
Scoop.it!

The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition

The Plasmodesmal Protein PDLP1 Localises to Haustoria-Associated Membranes during Downy Mildew Infection and Regulates Callose Deposition | Emerging Research in Plant Cell Biology | Scoop.it
The downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa) is a filamentous oomycete that invades plant cells via sophisticated but poorly understood structures called haustoria. Haustoria are separated from the host cell cytoplasm and surrounded by an extrahaustorial membrane (EHM) of unknown origin. In some interactions, including Hpa-Arabidopsis, haustoria are progressively encased by host-derived, callose-rich materials but the molecular mechanisms by which callose accumulates around haustoria remain unclear. Here, we report that PLASMODESMATA-LOCATED PROTEIN 1 (PDLP1) is expressed at high levels in Hpa infected cells. Unlike other plasma membrane proteins, which are often excluded from the EHM, PDLP1 is located at the EHM in Hpa-infected cells prior to encasement. The transmembrane domain and cytoplasmic tail of PDLP1 are sufficient to convey this localization. PDLP1 also associates with the developing encasement but this association is lost when encasements are fully mature. We found that the pdlp1,2,3 triple mutant is more susceptible to Hpa while overexpression of PDLP1 enhances plant resistance, suggesting that PDLPs enhance basal immunity against Hpa. Haustorial encasements are depleted in callose in pdlp1,2,3 mutant plants whereas PDLP1 over-expression elevates callose deposition around haustoria and across the cell surface. These data indicate that PDLPs contribute to callose encasement of Hpa haustoria and suggests that the deposition of callose at haustoria may involve similar mechanisms to callose deposition at plasmodesmata.

Via Suayib Üstün
more...
No comment yet.
Rescooped by Jennifer Mach from Plants and Microbes
Scoop.it!

Gregor Mendel Institute - Youssef Belkhadir (2014)

Gregor Mendel Institute - Youssef Belkhadir (2014) | Emerging Research in Plant Cell Biology | Scoop.it

A key question in biology is how organisms “adapt”, or acquire environment-dependent fitness advantages. Plants must grow fast enough to compete with their neighbours, while maintaining appropriate defences to survive in the presence of pathogens. Understanding how plants make the "decision" to keep safe from harm while growing is crucial to our quest for an abundant food supply and cheap, dependable sources of energy. In my laboratory we utilize of a complex array of technologies to understand how light and growth hormones signals allow plants to optimize the fluctuating investments they are making towards growth and defences in specific cells and organs but also at the population level. The laboratory aims at training a new breed of scientists who will not only be able to integrate plant developmental processes in the face of plant defences but will also understand plant defence responses in the context of environmental (light) and endogenous cues (hormones).


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

A plausible mechanism, based upon SHORT-ROOT movement, for regulating the number of cortex cell layers in roots

A plausible mechanism, based upon SHORT-ROOT movement, for regulating the number of cortex cell layers in roots | Emerging Research in Plant Cell Biology | Scoop.it

Formation of specialized cells and tissues at defined times and in specific positions is essential for the development of multicellular organisms. Often this developmental precision is achieved through intercellular signaling networks, which establish patterns of differential gene expression and ultimately the specification of distinct cell fates. Here we address the question of how the SHORT-ROOT (SHR) proteins from Arabidopsis thaliana (AtSHR), Brachypodium distachyon (BdSHR), and Oryza sativa (OsSHR1 and OsSHR2) function in patterning the root ground tissue. We find that all of the SHR proteins function as mobile signals in A. thalianaand all of the SHR homologs physically interact with the AtSHR binding protein, SCARECOW (SCR). Unlike AtSHR, movement of the SHR homologs was not limited to the endodermis. Instead, the SHR proteins moved multiple cell layers and determined the number of cortex, not endodermal, cell layers formed in the root. Our results in A. thaliana are consistent with a mechanism by which the regulated movement of the SHR transcription factor determines the number of cortex cell layers produced in the roots of B. distachyon and O. sativa. These data also provide a new model for ground tissue patterning in A. thaliana in which the ability to form a functional endodermis is spatially limited independently of SHR.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Antisense COOLAIR mediates the coordinated switching of chromatin states at FLC during vernalization

Antisense COOLAIR mediates the coordinated switching of chromatin states at FLC during vernalization | Emerging Research in Plant Cell Biology | Scoop.it

Long noncoding RNAs (lncRNAs) have been proposed to play important roles in gene regulation. However, their importance in epigenetic silencing and how specificity is determined remain controversial. We have investigated the cold-induced epigenetic switching mechanism involved in the silencing of Arabidopsis thaliana FLOWERING LOCUS C (FLC), which occurs during vernalization. Antisense transcripts, collectively named COOLAIR, are induced by prolonged cold before the major accumulation of histone 3 lysine 27 trimethylation (H3K27me3), characteristic of Polycomb silencing. We have found that COOLAIR is physically associated with the FLC locus and accelerates transcriptional shutdown of FLC during cold exposure. Removal of COOLAIR disrupted the synchronized replacement of H3K36 methylation with H3K27me3 at the intragenic FLC nucleation site during the cold. Consistently, genetic analysis showed COOLAIR and Polycomb complexes work independently in the cold-dependent silencing of FLC. Our data reveal a role for lncRNA in the coordinated switching of chromatin states that occurs during epigenetic regulation.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

High-Resolution Transcript Profiling of the Atypical Biotrophic Interaction between Theobroma cacao and the Fungal Pathogen Moniliophthora perniciosa

High-Resolution Transcript Profiling of the Atypical Biotrophic Interaction between Theobroma cacao and the Fungal Pathogen Moniliophthora perniciosa | Emerging Research in Plant Cell Biology | Scoop.it

Witches’ broom disease (WBD), caused by the hemibiotrophic fungusMoniliophthora perniciosa, is one of the most devastating diseases of Theobroma cacao, the chocolate tree. In contrast to other hemibiotrophic interactions, theWBD biotrophic stage lasts for months and is responsible for the most distinctive symptoms of the disease, which comprise drastic morphological changes in the infected shoots. Here, we used the dual RNA-seq approach to simultaneously assess the transcriptomes of cacao and M. perniciosa during their peculiar biotrophic interaction. Infection with M. perniciosa triggers massive metabolic reprogramming in the diseased tissues. Although apparently vigorous, the infected shoots are energetically expensive structures characterized by the induction of ineffective defense responses and by a clear carbon deprivation signature. Remarkably, the infection culminates in the establishment of a senescence process in the host, which signals the end of the WBD biotrophic stage. We analyzed the pathogen’s transcriptome in unprecedented detail and thereby characterized the fungal nutritional and infection strategies during WBD and identified putative virulence effectors. Interestingly, M. perniciosa biotrophic mycelia develop as long-term parasites that orchestrate changes in plant metabolism to increase the availability of soluble nutrients before plant death. Collectively, our results provide unique insight into an intriguing tropical disease and advance our understanding of the development of (hemi)biotrophic plant-pathogen interactions.

more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

The zigzag model of plant–microbe interactions: is it time to move on? - Pritchard - 2014 - Molecular Plant Pathology - Wiley Online Library

The zigzag model of plant–microbe interactions: is it time to move on? - Pritchard - 2014 - Molecular Plant Pathology - Wiley Online Library | Emerging Research in Plant Cell Biology | Scoop.it
more...
No comment yet.
Rescooped by Jennifer Mach from Plants and Microbes
Scoop.it!

Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014)

Frontiers in Plant-Microbe Interaction | Research Topics: Plant Immunity: From model systems to crops species (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Plants posses an intricate innate immune system that enables them to fight off most invading pathogens. Around the world, agriculture relies on robust disease resistance to ensure adequate food and feed production. Researchers and breeders are constantly generating new resistant crop varieties mostly employing the lengthy process of conventional breeding. Nonetheless, crop losses due to plant pathogens are estimated to be over 15% every year - the main cause of such losses is rapid evolution of new virulent races. In order to keep up with emerging pathogens, we need to gain a deeper and more systematic understanding of the immune system of our crops. During the past two decades, molecular understanding of plant innate immune signaling has been greatly expanded using dicotyledonous model systems such as Arabidopsis thaliana. Now, it is time to connect this volume of knowledge with the immune system of the crop species.

 

In this Research Topic we aim to collect manuscripts covering the current knowledge of the immune systems of major crop species. Specifically, we encourage the submission of manuscripts (Original Research, Hypothesis & Theory, Methods, Reviews, Mini Reviews, Perspective and Opinion) covering the following topics:

 

a. Manuscripts describing our current understanding of the plant immune system with a focus on crop species or comparative analyses between model systems and crops.

b. Manuscripts exploring how to best exploit our insight into genomes of plant pathogens and molecular understanding of effector function.
c. Manuscripts debating (novel) strategies of how to generate more resistant crop varieties. These might include biotechnological, social and economical aspects of crop improvement.

 

We anticipate that this Research Topic will become an important resource for plant immunologists especially those interested in comparative studies of plant innate immune systems of model systems and crop species.

 

Topic Editors

 

Benjamin Schwessinger
UC Davis
Davis, USA

 

Rebecca Bart
Donald Danforth Plant Science Center
St. Louis, USA

 

Gitta Coaker
University of California, Davis
Davis, USA

 

Ksenia V Krasileva
University of California Davis
Davis, USA


Via Kamoun Lab @ TSL
more...
No comment yet.
Rescooped by Jennifer Mach from Plants and Microbes
Scoop.it!

PLOS One: Functional Analysis of Hyaloperonospora arabidopsidis RXLR Effectors (2014)

PLOS One: Functional Analysis of Hyaloperonospora arabidopsidis RXLR Effectors (2014) | Emerging Research in Plant Cell Biology | Scoop.it

The biotrophic plant pathogen Hyaloperonospora arabidopsidis produces a set of putative effector proteins that contain the conserved RXLR motif. For most of these RXLR proteins the role during infection is unknown. Thirteen RXLR proteins from H. arabidopsidis strain Waco9 were analyzed for sequence similarities and tested for a role in virulence. The thirteen RXLR proteins displayed conserved N-termini and this N-terminal conservation was also found in the 134 predicted RXLR genes from the genome of H. arabidopsidis strain Emoy2. To investigate the effects of single RXLR effector proteins on plant defense responses, thirteen H. arabidopsidis Waco9 RXLR genes were expressed in Arabidopsis thaliana. Subsequently, these plants were screened for altered susceptibility to the oomycetes H. arabidopsidis and Phytophthora capsici, and the bacterial pathogen Pseudomonas syringae. Additionally, the effect of the RXLR proteins on flg22-triggered basal immune responses was assessed. Multifactorial analysis of results collated from all experiments revealed that, except for RXLR20, all RXLR effector proteins tested affected plant immunity. For RXLR9 this was confirmed using a P. syringae ΔCEL-mediated effector delivery system. Together, the results show that many H. arabidopsidis RXLR effectors have small effects on the plant immune response, suggesting that suppression of host immunity by this biotrophic pathogen is likely to be caused by the combined actions of effectors.


Via Kamoun Lab @ TSL
more...
No comment yet.
Scooped by Jennifer Mach
Scoop.it!

Genome-wide analysis of local chromatin packing in Arabidopsis thaliana

The spatial arrangement of interphase chromosomes in the nucleus is important for gene expression and genome function in animals and in plants. The recently developed Hi-C technology is an efficacious method to investigate genome packing. Here we present a detailed Hi-C map of the three-dimensional genome organization of the plant Arabidopsis thaliana. We find that local chromatin packing differs from the patterns seen in animals, with kilobasepair-sized segments that have much higher intra-chromosome interaction rates than neighboring regions, representing a dominant local structural feature of genome conformation in A. thaliana. These regions, which appear as positive strips on two-dimensional representations of chromatin interaction, are enriched in epigenetic marks H3K27me3, H3.1 and H3.3. We also identify over 400 insulator-like regions. Furthermore, although topologically associating domains (TADs), which are prominent in animals, are not an obvious feature of A. thaliana genome packing, we found over 1,000 regions that have properties of TAD boundaries, and a similar number of regions analogous to the interior of TADs. The insulator-like, TAD-boundary-like, and TAD-interior-like regions are each enriched for distinct epigenetic marks, and are each correlated with different gene expression levels. We conclude that epigenetic modifications, gene density, and transcriptional activity combine to shape the local packing of the A. thaliana nuclear genome.

more...
No comment yet.