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Rescooped by Jennifer Mach from Plant Biology Teaching Resources (Higher Education)
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Video: Leavitt's Lichens! (We like lichens too)

2 min video from the Field Museum, Chicago. "Steve Leavitt studies one of the world's most common but overlooked symbiotic systems, lichens. Using DNA analysis he explores the hidden world of lichen evolution..."

 

I like this bit: "There's a bit of evangelical passion as I try to share the knowledge and beauty of these lichens." Yea!


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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
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Silencing the mob: disrupting quorum sensing as a means to fight plant disease

Silencing the mob: disrupting quorum sensing as a means to fight plant disease | Emerging Research in Plant Cell Biology | Scoop.it

Bacteria are able to sense their population's density through a cell–cell communication system, termed ‘quorum sensing’ (QS). This system regulates gene expression in response to cell density through the constant production and detection of signalling molecules. These molecules commonly act as auto-inducers through the up-regulation of their own synthesis. Many pathogenic bacteria, including those of plants, rely on this communication system for infection of their hosts. The finding that the countering of QS-disrupting mechanisms exists in many prokaryotic and eukaryotic organisms offers a promising novel method to fight disease. During the last decade, several approaches have been proposed to disrupt QS pathways of phytopathogens, and hence to reduce their virulence. Such studies have had varied success in vivo, but most lend promising support to the idea that QS manipulation could be a potentially effective method to reduce bacterial-mediated plant disease. This review discusses the various QS-disrupting mechanisms found in both bacteria and plants, as well as the different approaches applied artificially to interfere with QS pathways and thus protect plant health.

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Niche and host-associated functional signatures of the root surface microbiome

Niche and host-associated functional signatures of the root surface microbiome | Emerging Research in Plant Cell Biology | Scoop.it

Plant microbiomes are critical to host adaptation and impact plant productivity and health. Root-associated microbiomes vary by soil and host genotype, but the contribution of these factors to community structure and metabolic potential has not been fully addressed. Here we characterize root microbial communities of two disparate agricultural crops grown in the same natural soil in a controlled and replicated experimental system. Metagenomic (genetic potential) analysis identifies a core set of functional genes associated with root colonization in both plant hosts, and metatranscriptomic (functional expression) analysis revealed that most genes enriched in the root zones are expressed. Root colonization requires multiple functional capabilities, and these capabilities are enriched at the community level. Differences between the root-associated microbial communities from different plants are observed at the genus or species level, and are related to root-zone environmental factors.


Via Stéphane Hacquard, Francis Martin, Ali Taheri
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Rescooped by Jennifer Mach from Plant roots and rhizosphere
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Transcription factors involved in controlling the expression of nitrate reductase genes in higher plants

Transcription factors involved in controlling the expression of nitrate reductase genes in higher plants | Emerging Research in Plant Cell Biology | Scoop.it

Nitrate reductase is a key enzyme in nitrogen assimilation, and it catalyzes the nitrate-to-nitrite reduction process in plants. A variety of factors, including nitrate, light, metabolites, phytohormones, low temperature, and drought, modulate the expression levels of nitrate reductase genes as well as nitrate reductase activity, which is consistent with its physiological role. Recently, several transcription factors involved in controlling the expression of nitrate reductase genes have been identified in Arabidopsis. NODULE-INCEPTION-like proteins (NLPs) are transcription factors responsible for nitrate-inducible expression of nitrate reductase genes. Since NLPs also control nitrate-inducible expression of genes encoding nitrate transporter, nitrite transporter, and nitrite reductase, the expression levels of nitrate reduction pathway-associated genes are coordinately modulated by NLPs in response to nitrate. LATERAL ORGAN BOUNDARIES DOMAIN (LBD) transcription factors (LBD37-LBD39) are strong candidates for transcription factors mediating negative feedback regulation in response to increases in the contents of nitrogen-containing metabolites, whereas LONG HYPOCOTYL 5 (HY5) that promotes photomorphogenesis in light may be a transcription factor involved in light-induced expression of a nitrate reductase gene. Furthermore, unidentified transcription factors likely mediate other signals and regulate the expression of nitrate reductase genes. This review presents a summary of our current knowledge of such transcription factors.


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Myosin VIII associates with microtubule ends and together with actin plays a role in guiding plant cell division

Myosin VIII associates with microtubule ends and together with actin plays a role in guiding plant cell division | Emerging Research in Plant Cell Biology | Scoop.it

Plant cells divide using the phragmoplast, a microtubule-based structure that directs vesicles secretion to the nascent cell plate. The phragmoplast forms at the cell center and expands to reach a specified site at the cell periphery, tens or hundreds of microns distant. The mechanism responsible for guiding the phragmoplast remains largely unknown. Here, using both moss and tobacco, we show that myosin VIII associates with the ends of phragmoplast microtubules and together with actin plays a role in guiding phragmoplast expansion to the cortical division site. Our data lead to a model whereby myosin VIII links phragmoplast microtubules to the cortical division site via actin filaments. Myosin VIII's motor activity along actin provides a molecular mechanism for steering phragmoplast expansion.

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De novo assembly of soybean wild relatives for pan-genome analysis of diversity and agronomic traits

De novo assembly of soybean wild relatives for pan-genome analysis of diversity and agronomic traits | Emerging Research in Plant Cell Biology | Scoop.it
Sequencing and de novo assembly of seven wild relatives of soybean yields insights relevant to crop domestication and improvement.

Via Ali Taheri
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Phenomic networks reveal largely independent root and shoot adjustment in waterlogged plants of Lotus japonicus

Phenomic networks reveal largely independent root and shoot adjustment in waterlogged plants of Lotus japonicus | Emerging Research in Plant Cell Biology | Scoop.it

Waterlogging imposes severe stress to the plant, and the interplay between root and aerial organs in the adjustment to this stress is poorly understood. A set of recombinant inbred lines (RILs) of Lotus japonicus (Gifu B-129 × Miyakojima MG-20) was subjected to control and waterlogging conditions for 21 d, and 12 traits related to leaf physiological functioning, root aerenchyma formation, shoot and root morphology, and dry mass accumulation were assessed to generate phenomic networks. The phenomic network became more complex under waterlogging as a result of the incorporation of root aerenchyma and dark-adapted Fv/Fm. Significant waterlogging-induced variation was found for stomatal conductance, dark-adapted Fv/Fm and aerenchyma. The RILs with stronger induction of aerenchyma in response to waterlogging tended to show reduced negative impact of this stress on root growth but suffered average impact on shoot growth. The RILs that retained higher stomatal conductance under waterlogging tended to retain higher dark-adapted Fv/Fm and shoot growth under waterlogging conditions but showed average impact on root traits. We propose a model where, although the stress experienced by the roots during waterlogging is transmitted to the shoot, shoots and roots deal with waterlogging in a less interdependent manner than often assumed.


Via Christophe Jacquet
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A Genome-Wide Association Study of the Maize Hypersensitive Defense Response Identifies Genes That Cluster in Related Pathways

A Genome-Wide Association Study of the Maize Hypersensitive Defense Response Identifies Genes That Cluster in Related Pathways | Emerging Research in Plant Cell Biology | Scoop.it

Much remains unknown of molecular events controlling the plant hypersensitive defense response (HR), a rapid localized cell death that limits pathogen spread and is mediated by resistance (R-) genes. Genetic control of the HR is hard to quantify due to its microscopic and rapid nature. Natural modifiers of the ectopic HR phenotype induced by an aberrant auto-active R-gene (Rp1-D21), were mapped in a population of 3,381 recombinant inbred lines from the maize nested association mapping population. Joint linkage analysis was conducted to identify 32 additive but no epistatic quantitative trait loci (QTL) using a linkage map based on more than 7000 single nucleotide polymorphisms (SNPs). Genome-wide association (GWA) analysis of 26.5 million SNPs was conducted after adjusting for background QTL. GWA identified associated SNPs that colocalized with 44 candidate genes. Thirty-six of these genes colocalized within 23 of the 32 QTL identified by joint linkage analysis. The candidate genes included genes predicted to be in involved programmed cell death, defense response, ubiquitination, redox homeostasis, autophagy, calcium signalling, lignin biosynthesis and cell wall modification. Twelve of the candidate genes showed significant differential expression between isogenic lines differing for the presence of Rp1-D21. Low but significant correlations between HR-related traits and several previously-measured disease resistance traits suggested that the genetic control of these traits was substantially, though not entirely, independent. This study provides the first system-wide analysis of natural variation that modulates the HR response in plants.

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New Phytologist: Different shades of JAZ during plant growth and defines (2014)

New Phytologist: Different shades of JAZ during plant growth and defines (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Ever since their discovery as key regulators of the jasmonate (JA) signaling pathway (Chini et al., 2007; Thines et al., 2007; Yan et al., 2007), repressor proteins of the JASMONATE ZIM-domain (JAZ) family have been rising stars in research on hormonal regulation of plant growth and defense. In plant cells, JAZ repressor proteins interact with an E3 ubiquitin ligase complex (SCFCOI1) that together function as a JA receptor. In resting cells, JAZs block the activity of transcriptional regulators of JA responses by physically binding to them. Upon perception of bioactive JAs, JAZ proteins are rapidly degraded via the ubiquitin/26S proteasome-dependent proteolytic pathway. This releases the JAZ-bound transcription factors, resulting in the activation of downstream JA responses (Fig. 1a). JAs play a dominant role in regulating defense responses against herbivorous insects and necrotrophic pathogens, and in adaptive responses to beneficial soilborne microbes (Wasternack & Hause, 2013; Pieterse et al., 2014). In addition, JAs have a signal function in a myriad other processes, including abiotic stress reactions and plant growth responses to environmental cues (Wasternack & Hause, 2013). The JA pathway functions in the context of a complex network of hormone-regulated signaling pathways that, depending on the environmental or developmental condition, can act antagonistically or synergistically on each other to finely balance resource allocation between growth and defense and minimize fitness tradeoffs (Pieterse et al., 2012; Vos et al., 2013). In the process of balancing plant growth and defense, gibberellins (GAs) have emerged as dominant antagonists of the JA signaling output (Hou et al., 2013).


Via Francis Martin, Kamoun Lab @ TSL
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David Kuykendall's curator insight, September 20, 4:30 PM

This is something I was interested in studying.

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Epigenetic reprogramming that prevents transgenerational inheritance of the vernalized state

Epigenetic reprogramming that prevents transgenerational inheritance of the vernalized state | Emerging Research in Plant Cell Biology | Scoop.it

The reprogramming of epigenetic states in gametes and embryos is essential for correct development in plants and mammals1. In plants, the germ line arises from somatic tissues of the flower, necessitating the erasure of chromatin modifications that have accumulated at specific loci during development or in response to external stimuli. If this process occurs inefficiently, it can lead to epigenetic states being inherited from one generation to the next2, 3, 4. However, in most cases, accumulated epigenetic modifications are efficiently erased before the next generation. An important example of epigenetic reprogramming in plants is the resetting of the expression of the floral repressor locusFLC in Arabidopsis thaliana. FLC is epigenetically silenced by prolonged cold in a process called vernalization. However, the locus is reactivated before the completion of seed development, ensuring the requirement for vernalization in every generation. In contrast to our detailed understanding of the polycomb-mediated epigenetic silencing induced by vernalization, little is known about the mechanism involved in the reactivation of FLC. Here we show that a hypomorphic mutation in the jumonji-domain-containing protein ELF6 impaired the reactivation of FLC in reproductive tissues, leading to the inheritance of a partially vernalized state. ELF6 has H3K27me3 demethylase activity, and the mutation reduced this enzymatic activity in planta. Consistent with this, in the next generation of mutant plants, H3K27me3 levels at the FLC locus stayed higher, and FLC expression remained lower, than in the wild type. Our data reveal an ancient role for H3K27 demethylation in the reprogramming of epigenetic states in plant and mammalian embryos5, 6, 7.

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Cross-bred crops get fit faster

Cross-bred crops get fit faster | Emerging Research in Plant Cell Biology | Scoop.it
Genetic engineering lags behind conventional breeding in efforts to create drought-resistant maize.
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Cell Host Microbes: Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life (2014)

Cell Host Microbes: Convergent Targeting of a Common Host Protein-Network by Pathogen Effectors from Three Kingdoms of Life (2014) | Emerging Research in Plant Cell Biology | Scoop.it

While conceptual principles governing plant immunity are becoming clear, its systems-level organization and the evolutionary dynamic of the host-pathogen interface are still obscure. We generated a systematic protein-protein interaction network of virulence effectors from the ascomycete pathogen Golovinomyces orontii and Arabidopsis thaliana host proteins. We combined this data set with corresponding data for the eubacterial pathogen Pseudomonas syringae and the oomycete pathogen Hyaloperonospora arabidopsidis. The resulting network identifies host proteins onto which intraspecies and interspecies pathogen effectors converge. Phenotyping of 124 Arabidopsis effector-interactor mutants revealed a correlation between intraspecies and interspecies convergence and several altered immune response phenotypes. Several effectors and the most heavily targeted host protein colocalized in subnuclear foci. Products of adaptively selected Arabidopsis genes are enriched for interactions with effector targets. Our data suggest the existence of a molecular host-pathogen interface that is conserved across Arabidopsis accessions, while evolutionary adaptation occurs in the immediate network neighborhood of effector targets.

 

Ralf Weßling, Petra Epple, Stefan Altmann,Yijian He, Li Yang, Stefan R. Henz, Nathan McDonald, Kristin Wiley, Kai Christian Bader, Christine Glaßer, M. Shahid Mukhtar, Sabine Haigis, Lila Ghamsari, Amber E. Stephens, Joseph R. Ecker, Marc Vidal, Jonathan D.G. Jones,Klaus F.X. Mayer, Emiel Ver Loren van Themaat, Detlef Weigel, Paul Schulze-Lefert, Jeffery L. Dangl, Ralph Panstruga, and Pascal Braun


Via Nicolas Denancé, Suayib Üstün
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CP's curator insight, September 12, 4:04 AM

add your insight...

Suayib Üstün's comment, September 12, 4:45 AM
HopBF1 is HopZ4!
Suayib Üstün's curator insight, September 12, 5:14 AM

HopBF1 is HopZ4...

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Climate refugia: joint inference from fossil records, species distribution models and phylogeography - Tansley Review

Climate refugia: joint inference from fossil records, species distribution models and phylogeography - Tansley Review | Emerging Research in Plant Cell Biology | Scoop.it

Climate refugia, locations where taxa survive periods of regionally adverse climate, are thought to be critical for maintaining biodiversity through the glacial–interglacial climate changes of the Quaternary. A critical research need is to better integrate and reconcile the three major lines of evidence used to infer the existence of past refugia – fossil records, species distribution models and phylogeographic surveys – in order to characterize the complex spatiotemporal trajectories of species and populations in and out of refugia. Here we review the complementary strengths, limitations and new advances for these three approaches. We provide case studies to illustrate their combined application, and point the way towards new opportunities for synthesizing these disparate lines of evidence. Case studies with European beech, Qinghai spruce and Douglas-fir illustrate how the combination of these three approaches successfully resolves complex species histories not attainable from any one approach. Promising new statistical techniques can capitalize on the strengths of each method and provide a robust quantitative reconstruction of species history. Studying past refugia can help identify contemporary refugia and clarify their conservation significance, in particular by elucidating the fine-scale processes and the particular geographic locations that buffer species against rapidly changing climate.

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Vitamin A Super Banana in human trials

Vitamin A Super Banana in human trials | Emerging Research in Plant Cell Biology | Scoop.it

The first human trial to test the efficacy of a genetically modified (GM) nutritionally enhanced banana is starting in the US. Conceived by researchers at the Queensland University of Technology (QUT) in Brisbane, Australia, to provide a good source...

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Characterization of novel wheat NBS domain-containing sequences and their utilization, in silico, for genome-scale R-gene mining

Characterization of novel wheat NBS domain-containing sequences and their utilization, in silico, for genome-scale R-gene mining | Emerging Research in Plant Cell Biology | Scoop.it

In crop improvement, the isolation, cloning and transfer of disease resistance genes (R-genes) is an ultimate goal usually starting from tentative R-gene analogs (RGAs) that are identified on the basis of their structure. For bread wheat, recent advances in genome sequencing are supporting the efforts of wheat geneticists worldwide. Among wheat R-genes, nucleotide-binding site (NBS)-encoding ones represent a major class. In this study, we have used a polymerase chain reaction-based approach to amplify and clone NBS-type RGAs from a bread wheat cultivar, ‘Salambo 80.’ Four novel complete ORF sequences showing similarities to previously reported R-genes/RGAs were used for in silico analyses. In a first step, where analyses were focused on the NBS domain, these sequences were phylogenetically assigned to two distinct groups: a first group close to leaf rust Lr21 resistance proteins; and a second one similar to cyst nematode resistance proteins. In a second step, sequences were used as initial seeds to walk up and downstream the NBS domain. This procedure enabled identifying 8 loci ranging in size between 2,115 and 7,653 bp. Ab initio gene prediction identified 8 gene models, among which two had complete ORFs. While GenBank survey confirmed the belonging of sequences to two groups, subsequent characterization using IWGSC genomic and proteomic data showed that the 8 gene models, reported in this study, were unique and their loci matched scaffolds on chromosome arms 1AS, 1BS, 4BS and 1DS. The gene model located on 1DS is a pseudo-Lr21 that was shown to have an NBS-LRR domain structure, while the potential association of the RGAs, here reported, is discussed. This study has produced novel R-gene-like loci and models in the wheat genome and provides the first steps toward further elucidation of their role in wheat disease resistance.


Via Christophe Jacquet, Guogen Yang, Ali Taheri
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Receptor kinase mediated control of primary active proton pumping at the plasma membrane

Receptor kinase mediated control of primary active proton pumping at the plasma membrane | Emerging Research in Plant Cell Biology | Scoop.it

Acidification of the cell wall space outside the plasma membrane is required for plant growth and is the result of proton extrusion by the plasma membrane-localized H+-ATPases. Here we show that the major plasma membrane proton pumps in Arabidopsis, AHA1 and AHA2, interact directly in vitro and in planta with PSY1R, a receptor kinase of the plasma membrane that serves as a receptor for the peptide growth hormone PSY1. The intracellular protein kinase domain of PSY1R phosphorylates AHA2/AHA1 at Thr-881, situated in the autoinhibitory Region I of the C-terminal domain. When expressed in a yeast heterologous expression system, the introduction of a negative charge at this position caused pump activation. Application of PSY1 to plant seedlings induced rapid in planta phosphorylation at Thr-881, concomitant with an instantaneous increase in proton efflux from roots. The direct interaction between AHA2 and PSY1R observed might provide a general paradigm for regulation of plasma membrane proton transport by receptor kinases.


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Genome-Wide Analysis of Alternative Splicing in Zea mays: Landscape and Genetic Regulation

Genome-Wide Analysis of Alternative Splicing in Zea mays: Landscape and Genetic Regulation | Emerging Research in Plant Cell Biology | Scoop.it

Alternative splicing enhances transcriptome diversity in all eukaryotes and plays a role in plant tissue identity and stress adaptation. To catalog new maize (Zea mays) transcripts and identify genomic loci that regulate alternative splicing, we analyzed over 90 RNA-seq libraries from maize inbred lines B73 and Mo17, as well as Syn10 doubled haploid lines (progenies from B73 × Mo17). Transcript discovery was augmented with publicly available data from 14 maize tissues, expanding the maize transcriptome by more than 30,000 and increasing the percentage of intron-containing genes that undergo alternative splicing to 40%. These newly identified transcripts greatly increase the diversity of the maize proteome, sometimes coding for entirely different proteins compared with their most similar annotated isoform. In addition to increasing proteome diversity, many genes encoding novel transcripts gained an additional layer of regulation by microRNAs, often in a tissue-specific manner. We also demonstrate that the majority of genotype-specific alternative splicing can be genetically mapped, with cis-acting quantitative trait loci (QTLs) predominating. A large number of trans-acting QTLswere also apparent, with nearly half located in regions not shown to contain genes associated with splicing. Taken together, these results highlight the currently underappreciated role that alternative splicing plays in tissue identity and genotypic variation in maize.

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Arabidopsis RRP6L1 and RRP6L2 Function in FLOWERING LOCUS C Silencing via Regulation of Antisense RNA Synthesis

Arabidopsis RRP6L1 and RRP6L2 Function in FLOWERING LOCUS C Silencing via Regulation of Antisense RNA Synthesis | Emerging Research in Plant Cell Biology | Scoop.it

The exosome complex functions in RNA metabolism and transcriptional gene silencing. Here, we report that mutations of two Arabidopsis genes encoding nuclear exosome componentsAtRRP6L1 and AtRRP6L2, cause de-repression of the main flowering repressor FLOWERING LOCUS C (FLC) and thus delay flowering in early-flowering Arabidopsis ecotypes. AtRRP6Lmutations affect the expression of known FLC regulatory antisense (AS) RNAs AS I and II, and cause an increase in Histone3 K4 trimethylation (H3K4me3) at FLC. AtRRP6L1 and AtRRP6L2 function redundantly in regulation of FLC and also act independently of the exosome core complex. Moreover, we discovered a novel, long non-coding, non-polyadenylated antisense transcript (ASL, for Antisense Long) originating from the FLC locus in wild type plants. The AtRRP6L proteins function as the main regulators of ASL synthesis, as these mutants show little or no ASL transcript. Unlike ASI/II, ASL associates with H3K27me3 regions of FLC, suggesting that it could function in the maintenance of H3K27 trimethylation during vegetative growth. AtRRP6L mutations also affect H3K27me3 levels and nucleosome density at the FLClocus. Furthermore, AtRRP6L1 physically associates with the ASL transcript and directly interacts with the FLC locus. We propose that AtRRP6L proteins participate in the maintenance of H3K27me3 at FLC via regulating ASL. Furthermore, AtRRP6Ls might participate in multipleFLC silencing pathways by regulating diverse antisense RNAs derived from the FLC locus.

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Membrane transporters mediating root signalling and adaptive responses to oxygen deprivation and soil flooding -

Membrane transporters mediating root signalling and adaptive responses to oxygen deprivation and soil flooding - | Emerging Research in Plant Cell Biology | Scoop.it

This review provides a comprehensive assessment of a previously unexplored topic: elucidating the role that plasma- and organelle-based membrane transporters play in plant-adaptive responses to flooding. We show that energy availability and metabolic shifts under hypoxia and anoxia are critical in regulating membrane-transport activity. We illustrate the high tissue and time dependence of this regulation, reveal the molecular identity of transporters involved and discuss the modes of their regulation. We show that both reduced oxygen availability and accumulation of transition metals in flooded roots result in a reduction in the cytosolic K+ pool, ultimately determining the cell's fate and transition to programmed cell death (PCD). This process can be strongly affected by hypoxia-induced changes in the amino acid pool profile and, specifically, ϒ-amino butyric acid (GABA) accumulation. It is suggested that GABA plays an important regulatory role, allowing plants to proceed with H2O2 signalling to activate a cascade of genes that mediate plant adaptation to flooding while at the same time, preventing the cell from entering a ‘suicide program’. We conclude that progress in crop breeding for flooding tolerance can only be achieved by pyramiding the numerous physiological traits that confer efficient energy maintenance, cytosolic ion homeostasis, and reactive oxygen species (ROS) control and detoxification.


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Arabidopsis RRP6L1 and RRP6L2 Function in FLOWERING LOCUS C Silencing via Regulation of Antisense RNA Synthesis

Arabidopsis RRP6L1 and RRP6L2 Function in FLOWERING LOCUS C Silencing via Regulation of Antisense RNA Synthesis | Emerging Research in Plant Cell Biology | Scoop.it

The exosome complex functions in RNA metabolism and transcriptional gene silencing. Here, we report that mutations of two Arabidopsis genes encoding nuclear exosome componentsAtRRP6L1 and AtRRP6L2, cause de-repression of the main flowering repressor FLOWERING LOCUS C (FLC) and thus delay flowering in early-flowering Arabidopsis ecotypes. AtRRP6Lmutations affect the expression of known FLC regulatory antisense (AS) RNAs AS I and II, and cause an increase in Histone3 K4 trimethylation (H3K4me3) at FLC. AtRRP6L1 and AtRRP6L2 function redundantly in regulation of FLC and also act independently of the exosome core complex. Moreover, we discovered a novel, long non-coding, non-polyadenylated antisense transcript (ASL, for Antisense Long) originating from the FLC locus in wild type plants. The AtRRP6L proteins function as the main regulators of ASL synthesis, as these mutants show little or no ASL transcript. Unlike ASI/II, ASL associates with H3K27me3 regions of FLC, suggesting that it could function in the maintenance of H3K27 trimethylation during vegetative growth. AtRRP6L mutations also affect H3K27me3 levels and nucleosome density at the FLClocus. Furthermore, AtRRP6L1 physically associates with the ASL transcript and directly interacts with the FLC locus. We propose that AtRRP6L proteins participate in the maintenance of H3K27me3 at FLC via regulating ASL. Furthermore, AtRRP6Ls might participate in multipleFLC silencing pathways by regulating diverse antisense RNAs derived from the FLC locus.

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PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014)

PLOS Pathogens: The Ins and Outs of Rust Haustoria (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Rust diseases caused by fungi of the order Pucciniales afflict a wide range of plants, including cereals, legumes, ornamentals, and fruit trees, and pose a serious threat to cropping systems and global food security. The obligate parasitic lifestyle of these fungi and their complex life cycles, often involving alternate hosts for the sexual and asexual stages, also make this group of pathogens of great biological interest. One of the most remarkable adaptations of rust fungi is the specialized infection structure that underpins the sustained biotrophic association with hosts; the haustorium (Figure 1A and C). This organ forms after penetration of the wall of a live host cell, expanding on the inner side of the cell wall while invaginating the surrounding host plasma membrane (Figure 1C). Through haustoria, the pathogen derives nutrients from the host and secretes virulence proteins called effectors, which are believed to be the key players that manipulate the physiological and immune responses of host cells [1]–[4]. Analogous terminal feeding structures have independently evolved in other organisms such as the haustorium in powdery mildews (ascomycetes) and downy mildews (oomycetes, not true fungi), and the arbuscules in arbuscular mycorrhizae, suggesting that such architecture represents a successful adaptation of these organisms to interact with their respective host plants [5], [6].


Via Kamoun Lab @ TSL
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Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014)

Scientific Reports: Secret lifestyles of Neurospora crassa: can it be a plant pathogen? (2014) | Emerging Research in Plant Cell Biology | Scoop.it

Neurospora crassa has a long history as an excellent model for genetic, cellular, and biochemical research. Although this fungus is known as a saprotroph, it normally appears on burned vegetations or trees after forest fires. However, due to a lack of experimental evidence, the nature of its association with living plants remains enigmatic. Here we report that Scots pine (Pinus sylvestris) is a host plant for N. crassa. The endophytic lifestyle of N. crassa was found in its interaction with Scots pine. Moreover, the fungus can switch to a pathogenic state when its balanced interaction with the host is disrupted. Our data reveal previously unknown lifestyles of N. crassa, which are likely controlled by both environmental and host factors. Switching among the endophytic, pathogenic, and saprotrophic lifestyles confers upon fungi phenotypic plasticity in adapting to changing environments and drives the evolution of fungi and associated plants.


Via Kamoun Lab @ TSL
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A faster Rubisco with potential to increase photosynthesis in crops

A faster Rubisco with potential to increase photosynthesis in crops | Emerging Research in Plant Cell Biology | Scoop.it

In photosynthetic organisms, D-ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is the major enzyme assimilating atmospheric CO2 into the biosphere1. Owing to the wasteful oxygenase activity and slow turnover of Rubisco, the enzyme is among the most important targets for improving the photosynthetic efficiency of vascular plants2, 3. It has been anticipated that introducing the CO2-concentrating mechanism (CCM) from cyanobacteria into plants could enhance crop yield4, 5, 6. However, the complex nature of Rubisco’s assembly has made manipulation of the enzyme extremely challenging, and attempts to replace it in plants with the enzymes from cyanobacteria and red algae have not been successful7, 8. Here we report two transplastomic tobacco lines with functional Rubisco from the cyanobacterium Synechococcus elongatus PCC7942 (Se7942). We knocked out the native tobacco gene encoding the large subunit of Rubisco by inserting the large and small subunit genes of the Se7942 enzyme, in combination with either the corresponding Se7942 assembly chaperone, RbcX, or an internal carboxysomal protein, CcmM35, which incorporates three small subunit-like domains9, 10. Se7942 Rubisco and CcmM35 formed macromolecular complexes within the chloroplast stroma, mirroring an early step in the biogenesis of cyanobacterial β-carboxysomes11, 12. Both transformed lines were photosynthetically competent, supporting autotrophic growth, and their respective forms of Rubisco had higher rates of CO2 fixation per unit of enzyme than the tobacco control. These transplastomic tobacco lines represent an important step towards improved photosynthesis in plants and will be valuable hosts for future addition of the remaining components of the cyanobacterial CCM, such as inorganic carbon transporters and the β-carboxysome shell proteins

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Plant Physiology: Efficient gene editing in tomato in the first generation using the CRISPR/Cas9 system (2014)

Plant Physiology: Efficient gene editing in tomato in the first generation using the CRISPR/Cas9 system (2014) | Emerging Research in Plant Cell Biology | Scoop.it

To test the efficacy of CRISPR/Cas9 in tomato, we chose to target a gene that, when function was disrupted, would result in a distinctive, immediately recognizable phenotype early in the plant tissue culture phase of Agrobacterium-mediated transformation. A CRISPR/Cas9 construct was designed to target neighboring sequences in the second exon of the tomato homolog of Arabidopsis ARGONAUTE7 (SlAGO7), because loss-of-function mutations are recessive and result in plants whose typical compound flat leaves become needle-like, or “wiry” (Fig. 1) (Lesley, 1928; Yifhar et al., 2012). SlAGO7 is required for the biogenesis of a class of small RNAs known as trans-acting short interfering RNAs (ta-siRNAs), which regulate organ polarity through post-transcriptional silencing of AUXIN RESPONSE FACTOR (ARF) genes (Husbands et al., 2009). Strong alleles of slago7 thus produce lower levels of ta-siRNAs and reduced ARF mRNA degradation, resulting in the first leaves of mutant plants having leaflets without petioles, and later formed leaves lacking laminae (Fig. 1C). These distinctive phenotypes allowed us to immediately identify first generation transformed (T0) plants in which both alleles of SlAGO7 might be mutated.


Via Kamoun Lab @ TSL
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Rescooped by Jennifer Mach from Plant-microbe interaction
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Autophagy as initiator or executioner of cell death: Trends in Plant Science

Autophagy as initiator or executioner of cell death: Trends in Plant Science | Emerging Research in Plant Cell Biology | Scoop.it

•Autophagy can suppress, initiate, or execute cell death depending on the biological context.

•Autophagy is an initiator of localized, hypersensitive response-associated cell death upon pathogen infection.

•Autophagy executes ‘formative’ vacuolar cell death and prevents ‘destructive’ necrosis in terminally differentiated cells.

•Homeostatic and anti-aging functions of autophagy complicate the dissection of its distinct roles in cell death.

Autophagy plays multiple, often antagonistic roles in plants. In particular, cytoprotective functions of autophagy are well balanced by cell death functions to compensate for the absence of apoptosis culminating in phagocytic clearance of dead cells. If autophagy is indeed required for plant programmed cell death (PCD), then what place does it occupy in the PCD pathways? Recent studies have examined the effects of impaired autophagy on pathogen-induced hypersensitive response (HR) and developmental PCD. While HR death was efficiently suppressed, inhibition of autophagy induced a switch from vacuolar PCD essential for development to necrosis. We therefore propose a dual role for autophagy in plant PCD: as an effector of HR PCD lying upstream of the ‘point-of-no-return’, and also as a downstream mechanism for clearance of terminally differentiated cells during developmental PCD.


Via Suayib Üstün
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Non-equivalent contributions of maternal and paternal genomes to early plant embryogenesis

Non-equivalent contributions of maternal and paternal genomes to early plant embryogenesis | Emerging Research in Plant Cell Biology | Scoop.it

Zygotic genome activation in metazoans typically occurs several hours to a day after fertilization, and thus maternal RNAs and proteins drive early animal embryo development1. In plants, despite several molecular studies of post-fertilization transcriptional activation, the timing of zygotic genome activation remains a matter of debate. For example, two recent reports that used different hybrid ecotype combinations for RNA sequence profiling of early Arabidopsis embryo transcriptomes came to divergent conclusions. One identified paternal contributions that varied by gene, but with overall maternal dominance2, while the other found that the maternal and paternal genomes are transcriptionally equivalent3. Here we assess paternal gene activation functionally in an isogenic background, by performing a large-scale genetic analysis of 49 EMBRYO DEFECTIVE genes and testing the ability of wild-type paternal alleles to complement phenotypes conditioned by mutant maternal alleles. Our results demonstrate that wild-type paternal alleles for nine of these genes are completely functional 2 days after pollination, with the remaining 40 genes showing partial activity beginning at 2, 3 or 5 days after pollination. Using our functional assay, we also demonstrate that different hybrid combinations exhibit significant variation in paternal allele activation, reconciling the apparently contradictory results of previous transcriptional studies2, 3. The variation in timing of gene function that we observe confirms that paternal genome activation does not occur in one early discrete step, provides large-scale functional evidence that maternal and paternal genomes make non-equivalent contributions to early plant embryogenesis, and uncovers an unexpectedly profound effect of hybrid genetic backgrounds on paternal gene activity.

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