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NaJAZh Regulates a Subset of Defense Responses against Herbivores and Spontaneous Leaf Necrosis in Nicotiana attenuata Plants

The JASMONATE ZIM DOMAIN (JAZ) proteins function as negative regulators of jasmonic acid signaling in plants. We cloned 12 JAZ genes from native tobacco (Nicotiana attenuata), including nine novel JAZs in tobacco, and examined their expression in plants that had leaves elicited by wounding or simulated herbivory. Most JAZ genes showed strong expression in the elicited leaves, but NaJAZg was mainly expressed in roots. Another novel herbivory-elicited gene, NaJAZh, was analyzed in detail. RNA interference suppression of this gene in inverted-repeat (ir)JAZh plants deregulated a specific branch of jasmonic acid-dependent direct and indirect defenses: irJAZh plants showed greater trypsin protease inhibitor activity, 17-hydroxygeranyllinalool diterpene glycosides accumulation, and emission of volatile organic compounds from leaves. Silencing of NaJAZh also revealed a novel cross talk in JAZ-regulated secondary metabolism, as irJAZh plants had significantly reduced nicotine levels. In addition, irJAZh spontaneously developed leaf necrosis during the transition to flowering. Because the lesions closely correlated with the elevated expression of programmed cell death genes and the accumulations of salicylic acid and hydrogen peroxide in the leaves, we propose a novel role of the NaJAZh protein as a repressor of necrosis and/or programmed cell death during plant development.

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Autophagic Degradation of the 26S Proteasome Is Mediated by the Dual ATG8/Ubiquitin Receptor RPN10 in Arabidopsis

Autophagic Degradation of the 26S Proteasome Is Mediated by the Dual ATG8/Ubiquitin Receptor RPN10 in Arabidopsis | Plant-Microbe Interaction | Scoop.it

Highlights•

The Arabidopsis 26S proteasome is degraded by ATG8-mediated autophagy

This degradation is induced by nitrogen starvation and proteasome inhibition

Proteasome inhibition stimulates extensive ubiquitylation of the complex

RPN10 acts as a proteaphagy receptor by binding ubiquitylated proteasomes and ATG8

Summary

Autophagic turnover of intracellular constituents is critical for cellular housekeeping, nutrient recycling, and various aspects of growth and development in eukaryotes. Here we show that autophagy impacts the other major degradative route involving the ubiquitin-proteasome system by eliminating 26S proteasomes, a process we termed proteaphagy. Using Arabidopsis proteasomes tagged with GFP, we observed their deposition into vacuoles via a route requiring components of the autophagy machinery. This transport can be initiated separately by nitrogen starvation and chemical or genetic inhibition of the proteasome, implying distinct induction mechanisms. Proteasome inhibition stimulates comprehensive ubiquitylation of the complex, with the ensuing proteaphagy requiring the proteasome subunit RPN10, which can simultaneously bind both ATG8 and ubiquitin. Collectively, we propose that Arabidopsis RPN10 acts as a selective autophagy receptor that targets inactive 26S proteasomes by concurrent interactions with ubiquitylated proteasome subunits/targets and lipidated ATG8 lining the enveloping autophagic membranes.


Via Christophe Jacquet, Suayib Üstün
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Team pinpoints genes that make plant stem cells, revealing origin of beefsteak tomatoes

Team pinpoints genes that make plant stem cells, revealing origin of beefsteak tomatoes | Plant-Microbe Interaction | Scoop.it
A team of scientists at Cold Spring Harbor Laboratory has identified a set of genes that control stem cell production in tomato. Mutations in these genes explain the origin of mammoth beefsteak tomatoes. More important, the research suggests how breeders can optimize fruit size in potentially any fruit-bearing crop.

Via Mary Williams
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Tansley Review: Genes and networks regulating root anatomy and architecture

Tansley Review: Genes and networks regulating root anatomy and architecture | Plant-Microbe Interaction | Scoop.it

The root is an excellent model for studying developmental processes that underlie plant anatomy and architecture. Its modular structure, the lack of cell movement and relative accessibility to microscopic visualization facilitate research in a number of areas of plant biology. In this review, we describe several examples that demonstrate how cell type-specific developmental mechanisms determine cell fate and the formation of defined tissues with unique characteristics. In the last 10 yr, advances in genome-wide technologies have led to the sequencing of thousands of plant genomes, transcriptomes and proteomes. In parallel with the development of these high-throughput technologies, biologists have had to establish computational, statistical and bioinformatic tools that can deal with the wealth of data generated by them. These resources provide a foundation for posing more complex questions about molecular interactions, and have led to the discovery of new mechanisms that control phenotypic differences. Here we review several recent studies that shed new light on developmental processes, which are involved in establishing root anatomy and architecture. We highlight the power of combining large-scale experiments with classical techniques to uncover new pathways in root development.


Via Francis Martin, Mary Williams
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Rescooped by Guogen Yang from Effectors and Plant Immunity
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Front. Plant Sci.: Comparative genomics of a cannabis pathogen reveals insight into the evolution of pathogenicity in Xanthomonas (2015)

Front. Plant Sci.: Comparative genomics of a cannabis pathogen reveals insight into the evolution of pathogenicity in Xanthomonas (2015) | Plant-Microbe Interaction | Scoop.it

Pathogenic bacteria in the genus Xanthomonas cause diseases on over 350 plant species, including cannabis (Cannabis sativa L.). Because of regulatory limitations, the biology of the Xanthomonas-cannabis pathosystem remains largely unexplored. To gain insight into the evolution of Xanthomonas strains pathogenic to cannabis, we sequenced the genomes of two geographically distinct Xanthomonas strains, NCPPB 3753 and NCPPB 2877, which were previously isolated from symptomatic plant tissue in Japan and Romania. Comparative multilocus sequence analysis of housekeeping genes revealed that they belong to Group 2, which comprises most of the described species of Xanthomonas. Interestingly, both strains lack the Hrp Type III secretion system and do not contain any of the known Type III effectors. Yet their genomes notably encode two key Hrp pathogenicity regulators HrpG and HrpX, and hrpG and hrpX are in the same genetic organization as in the other Group 2 xanthomonads. Promoter prediction of HrpX-regulated genes suggests the induction of an aminopeptidase, a lipase and two polygalacturonases upon plant colonization, similar to other plant-pathogenic xanthomonads. Genome analysis of the distantly related Xanthomonas maliensis strain 97M, which was isolated from a rice leaf in Mali, similarly demonstrated the presence of HrpG, HrpX and a HrpX-regulated polygalacturonase, and the absence of the Hrp Type III secretion system and known Type III effectors. Given the observation that some Xanthomonas strains across distinct taxa do not contain hrpG and hrpX, we speculate a stepwise evolution of pathogenicity, which involves (i) acquisition of key regulatory genes and cell wall-degrading enzymes, followed by (ii) acquisition of the Hrp type III secretion system, which is ultimately accompanied by (iii) successive acquisition of type III effectors.

 

Jacobs JM, Pesce C, Lefeuvre P and Koebnik R


Via Nicolas Denancé
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Cysteines under ROS attack in plants: a proteomics view

Cysteines under ROS attack in plants: a proteomics view | Plant-Microbe Interaction | Scoop.it
Plants generate reactive oxygen species (ROS) as part of their metabolism and in response to various external stress factors, potentially causing significant damage to biomolecules and cell structures. During the course of evolution, plants have adapted to ROS toxicity, and use ROS as signalling messengers that activate defence responses. Cysteine (Cys) residues in proteins are one of the most sensitive targets for ROS-mediated post-translational modifications, and they have become key residues for ROS signalling studies. The reactivity of Cys residues towards ROS, and their ability to react to different oxidation states, allow them to appear at the crossroads of highly dynamic oxidative events. As such, a redox-active cysteine can be present as S-glutathionylated (-SSG), disulfide bonded (S-S), sulfenylated (-SOH), sulfinylated (-SO2H), and sulfonylated (-SO3H). The sulfenic acid (-SOH) form has been considered as part of ROS-sensing pathways, as it leads to further modifications which affect protein structure and function. Redox proteomic studies are required to understand how and why cysteines undergo oxidative post-translational modifications and to identify the ROS-sensor proteins. Here, we update current knowledge of cysteine reactivity with ROS. Further, we give an overview of proteomic techniques that have been applied to identify different redox-modified cysteines in plants. There is a particular focus on the identification of sulfenylated proteins, which have the potential to be involved in plant signal transduction.

Via Christophe Jacquet
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Systematic humanization of yeast genes reveals conserved functions and genetic modularity

Systematic humanization of yeast genes reveals conserved functions and genetic modularity | Plant-Microbe Interaction | Scoop.it

To determine whether genes retain ancestral functions over a billion years of evolution and to identify principles of deep evolutionary divergence, we replaced 414 essential yeast genes with their human orthologs, assaying for complementation of lethal growth defects upon loss of the yeast genes. Nearly half (47%) of the yeast genes could be successfully humanized. Sequence similarity and expression only partly predicted replaceability. Instead, replaceability depended strongly on gene modules: Genes in the same process tended to be similarly replaceable (e.g., sterol biosynthesis) or not (e.g., DNA replication initiation). Simulations confirmed that selection for specific function can maintain replaceability despite extensive sequence divergence. Critical ancestral functions of many essential genes are thus retained in a pathway-specific manner, resilient to drift in sequences, splicing, and protein interfaces.


Via Niklaus Grunwald
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Xa39, a novel dominant gene conferring broad-spectrum resistance to Xanthomonas oryzae pv. oryzae in rice -

Xa39, a novel dominant gene conferring broad-spectrum resistance to Xanthomonas oryzae pv. oryzae in rice - | Plant-Microbe Interaction | Scoop.it
Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (Xoo), is one of the most devastating rice diseases worldwide. In this study, a rice introgression line (IL), FF329, which was identified from a BC1F4 population derived from the cross between donor PSBRC66 (P66) and recipient Huang-Hua-Zhan (HHZ), exhibited a typical hypersensitive response (HR) when inoculated with all 21 representative Xoo strains, consisting of 14 Philippines races and seven Chinese pathotypes. By contrast, the parents were highly susceptible to 10 of the tested strains and resistant or moderately susceptible to 11 strains, but without HR symptoms. Genetic analysis of the F2 population derived from the HHZ/FF329 cross with virulent Philippines race 6 (P6) and Chinese pathotype V (CV) revealed that BB resistance in FF329 was controlled by a single dominant gene. Because FF329 showed broad-spectrum BB resistance, different from both parents, the gene identified was novel and was designated Xa39. Two SSR markers, RM21 and RM206, located on rice chromosome 11, were linked to the target gene by bulked segregant analysis. A further six markers linked to Xa39 were identified in the region between RM21 and RM206 for fine gene mapping, and the Xa39 locus was refined to a 97·4 kb interval flanked by markers RM26985 and DM13 using a large F2 population. This gene provides rice breeders with a new option to incorporate BB resistance into newly developed cultivars.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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Nitric oxide is a ubiquitous signal for maintaining redox balance in plant cells: regulation of ascorbate peroxidase as a case study

Nitric oxide is a ubiquitous signal for maintaining redox balance in plant cells: regulation of ascorbate peroxidase as a case study | Plant-Microbe Interaction | Scoop.it
Oxidative and nitrosative stresses and their respective antioxidant responses are common metabolic adjustments operating in all biological systems. These stresses result from an increase in reactive oxygen species (ROS) and reactive nitrogen species (RNS) and an imbalance in the antioxidant response. Plants respond to ROS and RNS accumulation by increasing the level of the antioxidant molecules glutathione and ascorbate and by activating specific antioxidant enzymes. Nitric oxide (NO) is a free radical considered to be toxic or protective depending on its concentration, combination with ROS compounds, and subcellular localization. In this review we focus on the mechanisms of NO action in combination with ROS on the regulation of the antioxidant system in plants. In particular, we describe the redox post-translational modifications of cytosolic ascorbate peroxidase and its influence on enzyme activity. The regulation of ascorbate peroxidase activity by NO as a redox sensor of acute oxidative stress or as part of a hormone-induced signalling pathway leading to lateral root development is presented and discussed.

Via Christophe Jacquet
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Determinants of community structure in the global plankton interactome

Determinants of community structure in the global plankton interactome | Plant-Microbe Interaction | Scoop.it
Species interaction networks are shaped by abiotic and biotic factors. Here, as part of the Tara Oceans project, we studied the photic zone interactome using environmental factors and organismal abundance profiles and found that environmental factors are incomplete predictors of community structure. We found associations across plankton functional types and phylogenetic groups to be nonrandomly distributed on the network and driven by both local and global patterns. We identified interactions among grazers, primary producers, viruses, and (mainly parasitic) symbionts and validated network-generated hypotheses using microscopy to confirm symbiotic relationships. We have thus provided a resource to support further research on ocean food webs and integrating biological components into ocean models.

Via Francis Martin
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Rescooped by Guogen Yang from Effectors and Plant Immunity
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Cell: A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors (2015)

Cell: A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors (2015) | Plant-Microbe Interaction | Scoop.it

Defense against pathogens in multicellular eukaryotes depends on intracellular immune receptors, yet surveillance by these receptors is poorly understood. Several plant nucleotide-binding, leucine-rich repeat (NB-LRR) immune receptors carry fusions with other protein domains. The Arabidopsis RRS1-R NB-LRR protein carries a C-terminal WRKY DNA binding domain and forms a receptor complex with RPS4, another NB-LRR protein. This complex detects the bacterial effectors AvrRps4 or PopP2 and then activates defense. Both bacterial proteins interact with the RRS1 WRKY domain, and PopP2 acetylates lysines to block DNA binding. PopP2 and AvrRps4 interact with other WRKY domain-containing proteins, suggesting these effectors interfere with WRKY transcription factor-dependent defense, and RPS4/RRS1 has integrated a “decoy” domain that enables detection of effectors that target WRKY proteins. We propose that NB-LRR receptor pairs, one member of which carries an additional protein domain, enable perception of pathogen effectors whose function is to target that domain.

 

Panagiotis F. Sarris, Zane Duxbury, Sung Un Huh, Yan Ma, Cécile Segonzac, Jan Sklenar, Paul Derbyshire, Volkan Cevik, Ghanasyam Rallapalli, Simon B. Saucet, Lennart Wirthmueller, Frank L.H. Menke, Kee Hoon Sohn, Jonathan D.G. Jones


Via Nicolas Denancé
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Rescooped by Guogen Yang from Virology and Bioinformatics from Virology.ca
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Biostars - Bioinformatics Explained

Biostars - Bioinformatics Explained | Plant-Microbe Interaction | Scoop.it

Tutorials and Q+A Forum for bioinformatic tools. 17 000 + users!


Via Kathleen McLeod
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Kathleen McLeod's curator insight, May 21, 7:08 PM

Could be an interesting resource!

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Treasure Your Exceptions: Unusual Domains in Immune Receptors Reveal Host Virulence Targets: Cell

Treasure Your Exceptions: Unusual Domains in Immune Receptors Reveal Host Virulence Targets: Cell | Plant-Microbe Interaction | Scoop.it

Summary:

A mechanistic understanding of how plant pathogens modulate their hosts is critical for rationally engineered disease resistance in agricultural systems. Two new studies show that genomically paired plant immune receptors have incorporated decoy domains that structurally mimic pathogen virulence targets to monitor attempted host immunosuppression.


Via Freddy Monteiro, Elsa Ballini
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Freddy Monteiro's curator insight, May 21, 1:02 PM

This is a short introduction to the back-to-back pieces:

 

1. A Plant Immune Receptor Detects Pathogen Effectors that Target WRKY Transcription Factors www.cell.com/cell/abstract/S0092-8674(15)00441-9

 

2. A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity http://www.cell.com/cell/abstract/S0092-8674%2815%2900442-0

 

Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Uncovering hidden worlds of ocean biodiversity

Uncovering hidden worlds of ocean biodiversity | Plant-Microbe Interaction | Scoop.it
A bewildering swirl of tiny creatures dominates life in the oceans. More numerous than the stars in the universe, these organisms serve as the foundation of all marine food webs, recycling major elements and producing and consuming about half the organic matter generated on Earth each year (1). In this issue, five research articles from the Tara Oceans expedition (2–6) provide a vivid, potentially transformative view of the genetic diversity and interconnectivity of these unseen marine communities of viruses, bacteria, archaea, single-celled eukaryotes, and small planktonic animals (see the figure). Together, these studies deliver compelling evidence for extensive networks of previously hidden biological interactions in the sea.

The Tara Oceans expedition harkens back to 18th-century sailing voyages that explored uncharted worlds, including Darwin's voyage aboard the HMS Beagle and the Challenger expedition that heralded the beginning of modern oceanography. The 36-m schooner Tara departed Lorient, France, in 2008 and sailed through the Mediterranean Sea and into the Indian, South Atlantic, and Southern oceans (see the map). Tara visited coral reefs in the South Pacific Ocean and then sailed through the Panama Canal and back across the North Atlantic Ocean, arriving at her homeport nearly 3 years later. At hundreds of locations along the way, scientists and crew collected thousands of samples from surface waters, from the deep chlorophyll maximum layers where microscopic photosynthetic organisms accumulate, and from deeper waters.

Via Francis Martin
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Rescooped by Guogen Yang from MycorWeb Plant-Microbe Interactions
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Molecular mechanisms underlying the close association between soil Burkholderia and fungi

Molecular mechanisms underlying the close association between soil Burkholderia and fungi | Plant-Microbe Interaction | Scoop.it

Bacterial species belonging to the genus Burkholderia have been repeatedly reported to be associated with fungi but the extent and specificity of these associations in soils remain undetermined. To assess whether associations between Burkholderia and fungi are widespread in soils, we performed a co-occurrence analysis in an intercontinental soil sample collection. This revealed that Burkholderia significantly co-occurred with a wide range of fungi. To analyse the molecular basis of the interaction, we selected two model fungi frequently co-occurring with Burkholderia, Alternaria alternata and Fusarium solani, and analysed the proteome changes caused by cultivation with either fungus in the widespread soil inhabitant B. glathei, whose genome we sequenced. Co-cultivation with both fungi led to very similar changes in the B. glatheiproteome. Our results indicate that B. glathei significantly benefits from the interaction, which is exemplified by a lower abundance of several starvation factors that were highly expressed in pure culture. However, co-cultivation also gave rise to stress factors, as indicated by the increased expression of multidrug efflux pumps and proteins involved in oxidative stress response. Our data suggest that the ability of Burkholderia to establish a close association with fungi mainly lies in the capacities to utilize fungal-secreted metabolites and to overcome fungal defense mechanisms. This work indicates that beneficial interactions with fungi might contribute to the survival strategy of Burkholderia species in environments with sub-optimal conditions, including acidic soils.


Via Francis Martin
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Rescooped by Guogen Yang from Plant immunity and legume symbiosis
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RACK1, scaffolding heterotrimeric G protein and MAPK cascade: Trends in Plant Science

RACK1, scaffolding heterotrimeric G protein and MAPK cascade: Trends in Plant Science | Plant-Microbe Interaction | Scoop.it
Scaffold proteins of mitogen-activated protein kinase (MAPK) cascades play crucial roles in determining signal specificity, amplitude, and duration in yeast and mammals. Recently, RACK1 was identified as the first plant MAPK scaffold protein that connects heterotrimeric G protein with a MAPK cascade to form a unique signaling pathway in plant immunity.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant-Microbe Symbioses
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A review: Quorum sensing in Bradyrhizobium

A review: Quorum sensing in Bradyrhizobium | Plant-Microbe Interaction | Scoop.it
Quorum sensing (QS) systems are an important form of cellular communication in bacteria. QS systems are based on the synthesis and secretion of a chemical signal (autoinducer) that accumulates as a function of population growth until reaching a threshold concentration that permits coordinated expression of certain genes that regulate bacterial physiology and behavior. A wide variety of soil bacteria (rhizobia) capable of establishing symbiotic associations with plants produces small chemical signaling molecules to communicate among themselves for physiological adaptation to environmental changes. Most species of rhizobia associated with legume plants have QS systems that regulate their behavior in a variety of soil microhabitats, including the establishment of symbiosis with the host plant. Species of the large, complex genus Bradyrhizobium are ecologically and agriculturally important, but present knowledge is limited and fragmentary regarding their QS communication systems, types of autoinducer produced, and biological processes regulated by QS. Therefore, the objective was to review findings to date on QS mechanisms in Bradyrhizobium, and the role of these mechanisms in symbiosis development and bacterial survival strategies. Bacteria of genus Bradyrhizobium produce a variety of QS signaling molecules, some of which are not found in any other bacterial genus. Of particular interest are the synthesis of bradyoxetin by Bradyrhizobium japonicum and its role in symbiosis regulation, and the synthesis of various branched homoserine lactones (HSLs) by other Bradyrhizobium species. In peanut-nodulating strains, these HSLs are associated with the processes of biofilm formation, motility, and autoaggregation. A proposed model is presented of QS mechanisms in Bradyrhizobium strains and the physiological processes regulated. The findings reviewed here provide a basis for future studies of QS communication systems in rhizobia and of regulatory mechanisms in bacterial behavior and ecophysiology.

Via Jean-Michel Ané
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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From pond slime to rain forest: the evolution of ABA signalling and the acquisition of dehydration tolerance - Cuming - 2015 - New Phytologist - Wiley Online Library

From pond slime to rain forest: the evolution of ABA signalling and the acquisition of dehydration tolerance - Cuming - 2015 - New Phytologist - Wiley Online Library | Plant-Microbe Interaction | Scoop.it
Let us cast our minds back half a billion years and look around us. We do not see a green and pleasant land. Instead, we see a barren wasteland. We see a land without plants, the landscape comprising bare rock and its erosion products – at best a mineral sludge. But it was around this time that the first land plants emerged, evolving from pond slime – an aquatic algal ancestor most likely left on the banks of a receding body of water. Unlike today's climax vegetation, the first land plants were simple. They lacked the complex anatomical adaptations characteristic of the modern flora –ramifying root systems scavenging water from deep below the surface, vascular tissues to deliver this to aerial parts of the plant, whence it evaporates via the stomatal apertures of the leaves.

Via Mary Williams
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Mary Williams's curator insight, May 24, 3:34 AM

Great job drawing the reader into this topic, nice writing!

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The thioredoxin/peroxiredoxin/sulfiredoxin system: current overview on its redox function in plants and regulation by reactive oxygen and nitrogen species

The thioredoxin/peroxiredoxin/sulfiredoxin system: current overview on its redox function in plants and regulation by reactive oxygen and nitrogen species | Plant-Microbe Interaction | Scoop.it
In plants, the presence of thioredoxin (Trx), peroxiredoxin (Prx), and sulfiredoxin (Srx) has been reported as a component of a redox system involved in the control of dithiol–disulfide exchanges of target proteins, which modulate redox signalling during development and stress adaptation. Plant thiols, and specifically redox state and regulation of thiol groups of cysteinyl residues in proteins and transcription factors, are emerging as key components in the plant response to almost all stress conditions. They function in both redox sensing and signal transduction pathways. Scarce information exists on the transcriptional regulation of genes encoding Trx/Prx and on the transcriptional and post-transcriptional control exercised by these proteins on their putative targets. As another point of control, post-translational regulation of the proteins, such as S-nitrosylation and S-oxidation, is of increasing interest for its effect on protein structure and function. Special attention is given to the involvement of the Trx/Prx/Srx system and its redox state in plant signalling under stress, more specifically under abiotic stress conditions, as an important cue that influences plant yield and growth. This review focuses on the regulation of Trx and Prx through cysteine S-oxidation and/or S-nitrosylation, which affects their functionality. Some examples of redox regulation of transcription factors and Trx- and Prx-related genes are also presented.

Via Christophe Jacquet
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Rescooped by Guogen Yang from Plant Biology Teaching Resources (Higher Education)
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Traffic Lines: New Tools for Genetic Analysis in Arabidopsis thaliana

Traffic Lines: New Tools for Genetic Analysis in Arabidopsis thaliana | Plant-Microbe Interaction | Scoop.it

This paper summary is contributed by Dr. Clint Springer @clintspringer (http://www.sju.edu/about-sju/faculty-staff/faculty-experts/clint-springer-phd).

Scott Poethig’s group at the University of Pennsylvania has created an excellent new tool for use in genetic analysis studies of Arabidopsis thaliana. Using the “traffic lines” they have created, one can use a pair of seed-expressed green and red fluorescent transgenes that flank the mutation of interest to identify the genotype of mutants without the need for phenotypic analysis. This powerful tool cuts mutant analysis time substantially in all mutant genotypes and provides a way of determining genotype if a visible phenotype is not present. Because of the coverage of the “traffic line” insertions across the genome, one could make use of this resource in classroom studies of plant genetics to examine segregating populations as well mutant analysis. The “traffic lines” are available in both the Columbia and Landsberg erecta genetic backgrounds and can be ordered from the The Arabidopsis Information Resource center.

http://www.genetics.org/content/200/1/35.abstract


Via Mary Williams
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Mary Williams's curator insight, May 22, 3:06 PM

Thanks Clint for sharing that. If any of you see a paper you want to share with others interested in plant biology education like this, drop me a line and I can share here. Also, when the new platform for plant science launches later this year we can get a nice "journal club" going with contributions and discussions.

Rescooped by Guogen Yang from Plants and Microbes
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Nature: Phylogenetic structure and host abundance drive disease pressure in communities (2015)

Nature: Phylogenetic structure and host abundance drive disease pressure in communities (2015) | Plant-Microbe Interaction | Scoop.it

 

Pathogens play an important part in shaping the structure and dynamics of natural communities, because species are not affected by them equally1, 2. A shared goal of ecology and epidemiology is to predict when a species is most vulnerable to disease. A leading hypothesis asserts that the impact of disease should increase with host abundance, producing a ‘rare-species advantage’3, 4, 5. However, the impact of a pathogen may be decoupled from host abundance, because most pathogens infect more than one species, leading to pathogen spillover onto closely related species6, 7. Here we show that the phylogenetic and ecological structure of the surrounding community can be important predictors of disease pressure. We found that the amount of tissue lost to disease increased with the relative abundance of a species across a grassland plant community, and that this rare-species advantage had an additional phylogenetic component: disease pressure was stronger on species with many close relatives. We used a global model of pathogen sharing as a function of relatedness between hosts, which provided a robust predictor of relative disease pressure at the local scale. In our grassland, the total amount of disease was most accurately explained not by the abundance of the focal host alone, but by the abundance of all species in the community weighted by their phylogenetic distance to the host. Furthermore, the model strongly predicted observed disease pressure for 44 novel host species we introduced experimentally to our study site, providing evidence for a mechanism to explain why phylogenetically rare species are more likely to become invasive when introduced8, 9. Our results demonstrate how the phylogenetic and ecological structure of communities can have a key role in disease dynamics, with implications for the maintenance of biodiversity, biotic resistance against introduced weeds, and the success of managed plants in agriculture and forestry.


Se also News & Views 

http://www.nature.com/nature/journal/v520/n7548/full/520446a.html


Via Kamoun Lab @ TSL
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An Autophosphorylation Site Database for Leucine-Rich Repeat Receptor-Like Kinases in Arabidopsis thaliana

An Autophosphorylation Site Database for Leucine-Rich Repeat Receptor-Like Kinases in Arabidopsis thaliana | Plant-Microbe Interaction | Scoop.it
Leucine-rich repeat receptor-like kinases (LRR RLKs) form a large family of plant signaling proteins consisting of an extracellular domain connected by a single-pass transmembrane sequence to a cytoplasmic kinase domain. Autophosphorylation on specific Ser and/or Thr residues in the cytoplasmic domain is often critical for the activation of several LRR RLK family members with proven functional roles in plant growth regulation, morphogenesis, disease resistance, and stress responses. While identification and functional characterization of in vivo phosphorylation sites is ultimately required for full understanding of LRR RLK biology and function, bacterial expression of recombinant LRR RLK cytoplasmic catalytic domains for identification of in vitro autophosphorylation sites provides a useful resource for further targeted identification and functional analysis of in vivo sites. In this study we employed high-throughput cloning and a variety of mass spectrometry approaches to generate an autophosphorylation site database representative of more than 30% of the approximately 223 LRR RLKs in Arabidopsis thaliana. His-tagged constructs of complete cytoplasmic domains were used to identify a total of 591 phosphorylation events across 73 LRR RLKs, with 496 sites uniquely assigned to specific Ser (268 sites) or Thr (228 sites) residues in 68 LRR RLKs. Multiple autophosphorylation sites per LRR RLK were the norm, with an average of seven sites per cytoplasmic domain, while some proteins showed more than 20 unique autophosphorylation sites. The database was used to analyze trends in the localization of phosphorylation sites across cytoplasmic kinase subdomains, and to derive a statistically significant sequence motif for phosphoSer autophosphorylation.

Via Jean-Michel Ané
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Jean-Michel Ané's curator insight, May 21, 1:02 PM

That should be super useful but... where is this database??

Rescooped by Guogen Yang from Host Cell & Pathogen Interactions
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Secretion systems in Gram-negative bacteria: structural and mechanistic insights : Nature Reviews Microbiology : Nature Publishing Group

Secretion systems in Gram-negative bacteria: structural and mechanistic insights : Nature Reviews Microbiology : Nature Publishing Group | Plant-Microbe Interaction | Scoop.it

Via Kenzibit
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Rakesh Yashroy's curator insight, May 23, 8:33 PM

Type III secretory system of gram negative microbes is not found in gram +ive microbes. Thus the two membrane system (outer & inner membranes) of gram negative microbes may have some role in this secretory process e.g.

Rescooped by Guogen Yang from Plant-Microbe Symbioses
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Tall fescue cultivar and fungal endophyte combinations influence plant growth and root exudate composition

Tall fescue cultivar and fungal endophyte combinations influence plant growth and root exudate composition | Plant-Microbe Interaction | Scoop.it
Tall fescue [Lolium arundinaceum (Schreb.)] is a cool-season perennial grass used in pastures throughout the Southeastern United States. The grass can harbor a shoot-specific fungal endophyte (Epichloë coenophiala) thought to provide the plant with enhanced resistance to biotic and abiotic stresses. Because alkaloids produced by the common variety of the endophyte cause severe animal health issues, focus has been on replacing the common-toxic strain with novel varieties that do not produce the mammal-toxic alkaloids but maintain abiotic and biotic stress tolerance benefits. Little attention has been given to the influence of the plant-fungal symbiosis on rhizosphere processes. Therefore, our objective was to study the influence of this relationship on plant biomass production and root exudate composition in tall fescue cultivars PDF and 97TF1, which were either not infected with the endophyte (E-), infected with the common toxic endophyte (CTE+) strain or with one of two novel endophytes (AR542E+, AR584E+). Plants were grown sterile for 3 weeks after which plant biomass, total organic carbon, total phenolic content and detailed chemical composition of root exudates were determined. Plant biomass production and exudate phenolic and organic carbon content were influenced by endophyte status, tall fescue cultivar, and their interaction. GC-TOF MS identified 132 compounds, including lipids, carbohydrates and carboxylic acids. Cluster analysis showed that the interaction between endophyte and cultivar resulted in unique exudate profiles. This is the first detailed study to assess how endophyte infection, notably with novel endophytes, and tall fescue cultivar interact to influence root exudate composition. Our results illustrate that tall fescue cultivar and endophyte status can influence plant growth and root exudate composition, which may help explain the observed influence of this symbiosis on rhizosphere biogeochemical processes.

Via Jean-Michel Ané
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Rescooped by Guogen Yang from Rice Blast
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The small GTPase MoYpt7 is required for membrane fusion in autophagy and pathogenicity of Magnaporthe oryzae

The small GTPase MoYpt7 is required for membrane fusion in autophagy and pathogenicity of Magnaporthe oryzae | Plant-Microbe Interaction | Scoop.it
Rab GTPases are required for vesicle-vacuolar fusion during vacuolar biogenesis in fungi. To date, little is known about the biological functions of the Rab small GTPase components in Magnaporthe oryzae. In this study, we investigated MoYpt7 of M. oryzae, a homologue of the small Ras-like GTPase Ypt7 in Saccharomyces cerevisiae. Cellular localization assays showed that MoYpt7 was predominantly localized to vacuolar membranes. Using a targeted gene disruption strategy, a ΔMoYPT7 mutant was generated that exhibited defects in mycelial growth and production of conidia. The conidia of the ΔMoYPT7 mutant were malformed and defective in the formation of appressoria. Consequently, the ΔMoYPT7 mutant failed to cause disease in rice and barley. Furthermore, the ΔMoYPT7 mutant showed impairment in autophagy, breached cell wall integrity, and higher sensitivity to both calcium and heavy metal stress. Transformants constitutively expressing an active MoYPT7 allele (MoYPT7-CA, Gln67Leu) exhibited distinct phenotypes from the ΔMoYPT7 mutant. Expression of MoYPT7-CA in MoYpt7 reduced pathogenicity and produced more appressoria-forming single-septum conidia. These results indicate that MoYPT7 is required for fungal morphogenesis, vacuole fusion, autophagy, stress resistance, and pathogenicity in M. oryzae.

Via Elsa Ballini
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Rescooped by Guogen Yang from Plant-microbe interaction
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Cell: A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity (2015)

Cell: A Receptor Pair with an Integrated Decoy Converts Pathogen Disabling of Transcription Factors to Immunity (2015) | Plant-Microbe Interaction | Scoop.it

Microbial pathogens infect host cells by delivering virulence factors (effectors) that interfere with defenses. In plants, intracellular nucleotide-binding/leucine-rich repeat receptors (NLRs) detect specific effector interference and trigger immunity by an unknown mechanism. The Arabidopsis-interacting NLR pair, RRS1-R with RPS4, confers resistance to different pathogens, including Ralstonia solanacearum bacteria expressing the acetyltransferase effector PopP2. We show that PopP2 directly acetylates a key lysine within an additional C-terminal WRKY transcription factor domain of RRS1-R that binds DNA. This disrupts RRS1-R DNA association and activates RPS4-dependent immunity. PopP2 uses the same lysine acetylation strategy to target multiple defense-promoting WRKY transcription factors, causing loss of WRKY-DNA binding and transactivating functions needed for defense gene expression and disease resistance. Thus, RRS1-R integrates an effector target with an NLR complex at the DNA to switch a potent bacterial virulence activity into defense gene activation.

 

Clémentine Le Roux, Gaëlle Huet, Alain Jauneau, Laurent Camborde, Dominique Trémousaygue, Alexandra Kraut, Binbin Zhou, Marie Levaillant, Hiroaki Adachi, Hirofumi Yoshioka, Sylvain Raffaele, Richard Berthomé, Yohann Couté, Jane E. Parker, Laurent Deslandes


Via Nicolas Denancé, Jim Alfano, Suayib Üstün
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