Emerging Research in Plant Cell Biology
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An Arbor Embolism? Why Trees Die In Drought : NPR

An Arbor Embolism? Why Trees Die In Drought : NPR | Emerging Research in Plant Cell Biology | Scoop.it
Scientists who study forests say they've discovered something disturbing about the way prolonged drought affects trees. When drought dries out the soil, a tree has to suck harder to draw in water.
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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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Rescooped by Jennifer Mach from Plant immunity and legume symbiosis
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Post-translational regulation of plant immunity

Post-translational regulation of plant immunity | Emerging Research in Plant Cell Biology | Scoop.it

Highlights

•Phosphorylation is a rapid and transient switch for PTI.
• PTM links metabolic pathways important for defense.
• PTM of TSB1 counters pathogen virulence strategies.
• PTM at the host–pathogen interface during ETI.
• NPRs are regulators of both ETI and SAR.

Plants have evolved multi-layered molecular defense strategies to protect against pathogens. Plant immune signaling largely relies on post-translational modifications (PTMs) to induce rapid alterations of signaling pathways to achieve a response that is appropriate to the type of pathogen and infection pressure. In host cells, dynamic PTMs have emerged as powerful regulatory mechanisms that cells use to adjust their immune response. PTM is also a virulence strategy used by pathogens to subvert host immunity through the activities of effector proteins secreted into the host cell. Recent studies focusing on deciphering post-translational mechanisms underlying plant immunity have offered an in-depth view of how PTMs facilitate efficient immune responses and have provided a more dynamic and holistic view of plant immunity.


Via Christophe Jacquet
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CONSTANS imparts DNA sequence-specificity to the histone-fold NF-YB/NF-YC dimer

CONSTANS imparts DNA sequence-specificity to the histone-fold NF-YB/NF-YC dimer | Emerging Research in Plant Cell Biology | Scoop.it

CONSTANS imparts DNA sequence-specificity to the histone-fold NF-YB/NF-YC dimer

Nerina Gnesutta, Roderick W Kumimoto, Swadhin Swain, Matteo Chiara, Chamindika Siriwardana, David Stephen Horner, Ben F Holt, and Roberto Mantovani

Plant Cell 2017 tpc.16.00864; Advance Publication May 19, 2017; doi:10.1105/tpc.16.00864 OPEN


Via Mary Williams
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Wild tobacco genomes reveal the evolution of nicotine biosynthesis

Wild tobacco genomes reveal the evolution of nicotine biosynthesis | Emerging Research in Plant Cell Biology | Scoop.it

Nicotine, the signature alkaloid of Nicotiana species responsible for the addictive properties of human tobacco smoking, functions as a defensive neurotoxin against attacking herbivores. However, the evolution of the genetic features that contributed to the assembly of the nicotine biosynthetic pathway remains unknown. We sequenced and assembled genomes of two wild tobaccos, Nicotiana attenuata (2.5 Gb) and Nicotiana obtusifolia (1.5 Gb), two ecological models for investigating adaptive traits in nature. We show that after the Solanaceae whole-genome triplication event, a repertoire of rapidly expanding transposable elements (TEs) bloated these Nicotiana genomes, promoted expression divergences among duplicated genes, and contributed to the evolution of herbivory-induced signaling and defenses, including nicotine biosynthesis. The biosynthetic machinery that allows for nicotine synthesis in the roots evolved from the stepwise duplications of two ancient primary metabolic pathways: the polyamine and nicotinamide adenine dinucleotide (NAD) pathways. In contrast to the duplication of the polyamine pathway that is shared among several solanaceous genera producing polyamine-derived tropane alkaloids, we found that lineage-specific duplications within the NAD pathway and the evolution of root-specific expression of the duplicated Solanaceae-specific ethylene response factor that activates the expression of all nicotine biosynthetic genes resulted in the innovative and efficient production of nicotine in the genus Nicotiana. Transcription factor binding motifs derived from TEs may have contributed to the coexpression of nicotine biosynthetic pathway genes and coordinated the metabolic flux. Together, these results provide evidence that TEs and gene duplications facilitated the emergence of a key metabolic innovation relevant to plant fitness.

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Bypassing Negative Epistasis on Yield in Tomato Imposed by a Domestication Gene

Bypassing Negative Epistasis on Yield in Tomato Imposed by a Domestication Gene | Emerging Research in Plant Cell Biology | Scoop.it

Selection for inflorescence architecture with improved flower production and yield is common to many domesticated crops. However, tomato inflorescences resemble wild ancestors, and breeders avoided excessive branching because of low fertility. We found branched variants carry mutations in two related transcription factors that were selected independently. One founder mutation enlarged the leaf-like organs on fruits and was selected as fruit size increased during domestication. The other mutation eliminated the flower abscission zone, providing “jointless” fruit stems that reduced fruit dropping and facilitated mechanical harvesting. Stacking both beneficial traits caused undesirable branching and sterility due to epistasis, which breeders overcame with suppressors. However, this suppression restricted the opportunity for productivity gains from weak branching. Exploiting natural and engineered alleles for multiple family members, we achieved a continuum of inflorescence complexity that allowed breeding of higher-yielding hybrids. Characterizing and neutralizing similar cases of negative epistasis could improve productivity in many agricultural organisms.

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Rescooped by Jennifer Mach from Plant pathogenic fungi
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Exocytosis for endosymbiosis: membrane trafficking pathways for development of symbiotic membrane compartments

Exocytosis for endosymbiosis: membrane trafficking pathways for development of symbiotic membrane compartments | Emerging Research in Plant Cell Biology | Scoop.it
Highlights 
• SNARES and EXOCYST components conserved for AM symbiosis. 
• An exocytotic pathway shared by AM symbiosis and rhizobium-legume symbiosis. 
• EXO70i is essential for polarized exocytosis of membrane during AM symbiosis. 
• Multiple exocytosis pathways operate during endosymbiosis.

During endosymbiosis with arbuscular mycorrhizal fungi or rhizobial bacteria, the microbial symbionts are housed within membrane-bound compartments in root cortex or nodule cells respectively. Their development involves polarized deposition of membrane around the symbionts as they enter the cells and the membranes show functional specialization, including transporters that mediate nutrient transfer between host and symbiont. The cellular changes associated with development of these compartments point to membrane deposition via exocytosis and over the past few years, researchers have uncovered several proteins within the exocytotic pathway that are required for development of endosymbiotic membrane compartments. The emerging theme is that unique membrane trafficking homologs or splice variants have evolved to enable exocytosis during endosymbiosis.

Via Pierre-Marc Delaux, Francis Martin, Steve Marek
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Hybrid incompatibility caused by an epiallele

Hybrid incompatibility caused by an epiallele | Emerging Research in Plant Cell Biology | Scoop.it

Hybrid incompatibility resulting from deleterious gene combinations is thought to be an important step toward reproductive isolation and speciation. Here, we demonstrate involvement of a silent epiallele in hybrid incompatibility. In Arabidopsis thaliana accession Cvi-0, one of the two copies of a duplicated histidine biosynthesis gene, HISN6A, is mutated, making HISN6B essential. In contrast, in accession Col-0, HISN6A is essential because HISN6B is not expressed. Owing to these differences, Cvi-0 × Col-0 hybrid progeny that are homozygous for both Cvi-0 HISN6A and Col-0 HISN6B do not survive. We show that HISN6B of Col-0 is not a defective pseudogene, but a stably silenced epiallele. Mutating HISTONE DEACETYLASE 6 (HDA6), or the cytosine methyltransferase genes MET1 or CMT3, erases HISN6B's silent locus identity, reanimating the gene to circumvent hisn6a lethality and hybrid incompatibility. These results show that HISN6-dependent hybrid lethality is a revertible epigenetic phenomenon and provide additional evidence that epigenetic variation has the potential to limit gene flow between diverging populations of a species.

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Rescooped by Jennifer Mach from Phytophthora biology
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Millions of California oak trees are dying

Millions of California oak trees are dying | Emerging Research in Plant Cell Biology | Scoop.it
A pathogen causing a phenomenon known as ‘sudden oak death’ has killed millions of oak and tanoak trees in California’s coastal forests since 1995.

Via Niklaus Grunwald
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Rescooped by Jennifer Mach from Plants and Microbes
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Molecular Plant: Effector–Decoy Pairs: Another Countermeasure Emerging during Host–Microbe Co-evolutionary Arms Races? (2017)

Molecular Plant: Effector–Decoy Pairs: Another Countermeasure Emerging during Host–Microbe Co-evolutionary Arms Races? (2017) | Emerging Research in Plant Cell Biology | Scoop.it
Plant pathogenic microbes pose a significant threat to food production, collectively affecting all cultivated crops. Given the impact of these pathogens on food security, there continues to be an urgent need to understand and exploit the biology of pathogenesis, plant susceptibility, and immunity in crop systems. Consequently, intense research efforts have helped define the molecular and evolutionary events that underpin plant-microbe interactions.

Via Nicolas Denancé, Kamoun Lab @ TSL
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Rescooped by Jennifer Mach from MycorWeb Plant-Microbe Interactions
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Ustilago maydis effectors and their impact on virulence : Nature Reviews Microbiology

Ustilago maydis effectors and their impact on virulence : Nature Reviews Microbiology | Emerging Research in Plant Cell Biology | Scoop.it
Biotrophic fungal plant pathogens establish an intimate relationship with their host to support the infection process. Central to this strategy is the secretion of a range of protein effectors that enable the pathogen to evade plant immune defences and modulate host metabolism to meet its needs. In this Review, using the smut fungus Ustilago maydis as an example, we discuss new insights into the effector repertoire of smut fungi that have been gained from comparative genomics and discuss the molecular mechanisms by which U. maydis effectors change processes in the plant host. Finally, we examine how the expression of effector genes and effector secretion are coordinated with fungal development in the host.

Via Francis Martin
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Rescooped by Jennifer Mach from Plant immunity and legume symbiosis
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O-Acyl Sugars Protect a Wild Tobacco from Both Native Fungal Pathogens and a Specialist Herbivore

O-Acyl Sugars Protect a Wild Tobacco from Both Native Fungal Pathogens and a Specialist Herbivore | Emerging Research in Plant Cell Biology | Scoop.it
O-Acyl sugars (O-AS) are abundant trichome-specific metabolites that function as indirect defenses against herbivores of the wild tobacco Nicotiana attenuata; whether they also function as generalized direct defenses against herbivores and pathogens remains unknown. We characterized natural variation in O-AS among 26 accessions and examined their influence on two native fungal pathogens, Fusarium brachygibbosum U4 and Alternaria sp. U10, and the specialist herbivore Manduca sexta. At least 15 different O-AS structures belonging to three classes were found in N. attenuata leaves. A 3-fold quantitative variation in total leaf O-AS was found among the natural accessions. Experiments with natural accessions and crosses between high- and low-O-AS accessions revealed that total O-AS levels were associated with resistance against herbivores and pathogens. Removing O-AS from the leaf surface increased M. sexta growth rate and plant fungal susceptibility. O-AS supplementation in artificial diets and germination medium reduced M. sexta growth and fungal spore germination, respectively. Finally, silencing the expression of a putative branched-chain α-ketoacid dehydrogenase E1 β-subunit-encoding gene (NaBCKDE1B) in the trichomes reduced total leaf O-AS by 20% to 30% and increased susceptibility to Fusarium pathogens. We conclude that O-AS function as direct defenses to protect plants from attack by both native pathogenic fungi and a specialist herbivore and infer that their diversification is likely shaped by the functional interactions among these biotic stresses.

Via Christophe Jacquet
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Rescooped by Jennifer Mach from Plant-Microbe Symbiosis
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Communication in the Phytobiome

Communication in the Phytobiome | Emerging Research in Plant Cell Biology | Scoop.it
The phytobiome is composed of plants, their environment, and diverse interacting microscopic and macroscopic organisms, which together influence plant health and productivity. These organisms form complex networks that are established and regulated through nutrient cycling, competition, antagonism, and chemical communication mediated by a diverse array of signaling molecules. Integration of knowledge of signaling mechanisms with that of phytobiome members and their networks will lead to a new understanding of the fate and significance of these signals at the ecosystem level. Such an understanding could lead to new biological, chemical, and breeding strategies to improve crop health and productivity.


Via Jean-Michel Ané
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Rescooped by Jennifer Mach from Plant immunity and legume symbiosis
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The highly buffered Arabidopsis immune signaling network conceals the functions of its components

The highly buffered Arabidopsis immune signaling network conceals the functions of its components | Emerging Research in Plant Cell Biology | Scoop.it
Plant immunity protects plants from numerous potentially pathogenic microbes. The biological network that controls plant inducible immunity must function effectively even when network components are targeted and disabled by pathogen effectors. Network buffering could confer this resilience by allowing different parts of the network to compensate for loss of one another’s functions. Networks rich in buffering rely on interactions within the network, but these mechanisms are difficult to study by simple genetic means. Through a network reconstitution strategy, in which we disassemble and stepwise reassemble the plant immune network that mediates Pattern-Triggered-Immunity, we have resolved systems-level regulatory mechanisms underlying the Arabidopsis transcriptome response to the immune stimulant flagellin-22 (flg22). These mechanisms show widespread evidence of interactions among major sub-networks—we call these sectors—in the flg22-responsive transcriptome. Many of these interactions result in network buffering. Resolved regulatory mechanisms show unexpected patterns for how the jasmonate (JA), ethylene (ET), phytoalexin-deficient 4 (PAD4), and salicylate (SA) signaling sectors control the transcriptional response to flg22. We demonstrate that many of the regulatory mechanisms we resolved are not detectable by the traditional genetic approach of single-gene null-mutant analysis. Similar to potential pathogenic perturbations, null-mutant effects on immune signaling can be buffered by the network.

Via Christophe Jacquet
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Rescooped by Jennifer Mach from Microbes, plant immunity, and crop science
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Mol. Plant.: Emerging Jasmonate Transporters (2017)

Mol. Plant.: Emerging Jasmonate Transporters (2017) | Emerging Research in Plant Cell Biology | Scoop.it
Empty descriJasmonic acid (JA) and methyl jasmonate (MeJA) are highly mobile and, when applied to intact plants, these compounds powerfully modulate gene expression. Moreover, activation of jasmonate-responsive genes usually occurs in tissues distal to the treatments. It therefore comes as no surprise that there are jasmonate transporters; these proteins are only now emerging and their discovery is important for a number of reasons. Firstly, biologically active jasmonates such as jasmonoyl-isoleucine (JA-Ile) are potent regulators that are made in small quantities and that need to be delivered to the correct cellular and subcellular sites. Secondly, jasmonates act to redirect resources from growth to defense. For example, when shoots are wounded, jasmonates help to coordinate the appropriate growth of roots so that organ growth rates are balanced even when a distal part of the plant is damaged. Moreover, some plants (Arabidopsis is an example) produce large quantities of the JA-Ile precursor JA upon wounding. JA and/or its immediate precursor can be transported from cell to cell and even from shoot to root (Gasperini et al., 2015; Figure 1A–1C ). The mechanisms underlying this transport need to be identified. However, a difficulty for the jasmonate field is that many studies of JA/JA-Ile transport have used exogenous jasmonates applied at sometimes non-physiological levels to plant tissues. These studies can be difficult to interpret, so the discovery of jasmonate transporter mutants represents a welcome breakthrough. Among these is the newly reported jasmonate transporter (JAT1) from Arabidopsis (Li et al., 2017).ption

Via Nicolas Denancé
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Autophagy as an emerging arena for plant–pathogen interactions

Autophagy as an emerging arena for plant–pathogen interactions | Emerging Research in Plant Cell Biology | Scoop.it

Highlights

• Autophagy is an integral part of plant–pathogen interactions.
• A large variety of microbial pathogens target or are targeted by plant autophagy.
• Autophagy in eukaryotic microbial pathogens is essential for pathogenesis.
• Plant autophagy participates in defense responses against invading microbes.
• Successful pathogens have evolved strategies to manipulate plant autophagy.



Autophagy is a highly conserved degradation and recycling process that controls cellular homeostasis, stress adaptation, and programmed cell death in eukaryotes. Emerging evidence indicates that autophagy is a key regulator of plant innate immunity and contributes with both pro-death and pro-survival functions to antimicrobial defences, depending on the pathogenic lifestyle. In turn, several pathogens have co-opted and evolved strategies to manipulate host autophagy pathways to the benefit of infection, while some eukaryotic microbes require their own autophagy machinery for successful pathogenesis. In this review, we present and discuss recent advances that exemplify the important role of pro- and antimicrobial autophagy in plant–pathogen interactions.


Via Christophe Jacquet, Suayib Üstün
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Monoterpenes support systemic acquired resistance within and between plants

Monoterpenes support systemic acquired resistance within and between plants | Emerging Research in Plant Cell Biology | Scoop.it

Via Mary Williams
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uORF-mediated translation allows engineered plant disease resistance without fitness costs

uORF-mediated translation allows engineered plant disease resistance without fitness costs | Emerging Research in Plant Cell Biology | Scoop.it
Controlling plant disease has been a struggle for humankind since the advent of agriculture. Studies of plant immune mechanisms have led to strategies of engineering resistant crops through ectopic transcription of plants’ own defence genes, such as the master immune regulatory gene NPR1 (ref. 1). However, enhanced resistance obtained through such strategies is often associated with substantial penalties to fitness2, making the resulting products undesirable for agricultural applications. To remedy this problem, we sought more stringent mechanisms of expressing defence proteins. On the basis of our latest finding that translation of key immune regulators, such as TBF1 (ref. 3), is rapidly and transiently induced upon pathogen challenge (see accompanying paper4), we developed a ‘TBF1-cassette’ consisting of not only the immune-inducible promoter but also two pathogen-responsive upstream open reading frames (uORFsTBF1) of the TBF1 gene. Here we demonstrate that inclusion of uORFsTBF1-mediated translational control over the production of snc1-1 (an autoactivated immune receptor) in Arabidopsis thaliana and AtNPR1 in rice enables us to engineer broad-spectrum disease resistance without compromising plant fitness in the laboratory or in the field. This broadly applicable strategy may lead to decreased pesticide use and reduce the selective pressure for resistant pathogens.

Via Francis Martin, Christophe Jacquet
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The evolutionary significance of polyploidy : Nature Reviews Genetics : Nature Research

The evolutionary significance of polyploidy : Nature Reviews Genetics : Nature Research | Emerging Research in Plant Cell Biology | Scoop.it
Polyploidy, or the duplication of entire genomes, has been observed in prokaryotic and eukaryotic organisms, and in somatic and germ cells. The consequences of polyploidization are complex and variable, and they differ greatly between systems (clonal or non-clonal) and species, but the process has often been considered to be an evolutionary 'dead end'. Here, we review the accumulating evidence that correlates polyploidization with environmental change or stress, and that has led to an increased recognition of its short-term adaptive potential. In addition, we discuss how, once polyploidy has been established, the unique retention profile of duplicated genes following whole-genome duplication might explain key longer-term evolutionary transitions and a general increase in biological complexity.

Via Francis Martin, Steve Marek
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Long-read sequencing uncovers the adaptive topography of a carnivorous plant genome

Long-read sequencing uncovers the adaptive topography of a carnivorous plant genome | Emerging Research in Plant Cell Biology | Scoop.it

Utricularia gibba, the humped bladderwort, is a carnivorous plant that retains a tiny nuclear genome despite at least two rounds of whole genome duplication (WGD) since common ancestry with grapevine and other species. We used a third-generation genome assembly with several complete chromosomes to reconstruct the two most recent lineage-specific ancestral genomes that led to the modern U. gibba genome structure. Patterns of subgenome dominance in the most recent WGD, both architectural and transcriptional, are suggestive of allopolyploidization, which may have generated genomic novelty and led to instantaneous speciation. Syntenic duplicates retained in polyploid blocks are enriched for transcription factor functions, whereas gene copies derived from ongoing tandem duplication events are enriched in metabolic functions potentially important for a carnivorous plant. Among these are tandem arrays of cysteine protease genes with trap-specific expression that evolved within a protein family known to be useful in the digestion of animal prey. Further enriched functions among tandem duplicates (also with trap-enhanced expression) include peptide transport (intercellular movement of broken-down prey proteins), ATPase activities (bladder-trap acidification and transmembrane nutrient transport), hydrolase and chitinase activities (breakdown of prey polysaccharides), and cell-wall dynamic components possibly associated with active bladder movements. Whereas independently polyploid Arabidopsis syntenic gene duplicates are similarly enriched for transcriptional regulatory activities, Arabidopsis tandems are distinct from those of U. gibba, while still metabolic and likely reflecting unique adaptations of that species. Taken together, these findings highlight the special importance of tandem duplications in the adaptive landscapes of a carnivorous plant genome.

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Rescooped by Jennifer Mach from Plant immunity and legume symbiosis
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NLR diversity, helpers and integrated domains: making sense of the NLR IDentity

NLR diversity, helpers and integrated domains: making sense of the NLR IDentity | Emerging Research in Plant Cell Biology | Scoop.it
Plant innate immunity relies on genetically predetermined repertoires of immune receptors to detect pathogens and trigger an effective immune response. A large proportion of these receptors are from the Nucletoide Binding Leucine Rich Repeat (NLR) gene family. As plants live longer than most pathogens, maintaining diversity of NLRs and deploying efficient ‘pathogen traps’ is necessary to withstand the evolutionary battle. In this review, we summarize the sources of diversity in NLR plant immune receptors giving an overview of genomic, regulatory as well as functional studies, including the latest concepts of NLR helpers and NLRs with integrated domains.

Via Christophe Jacquet
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From Pine Cones to Read Clouds: Rescaffolding the Megagenome of Sugar Pine (Pinus lambertiana)

From Pine Cones to Read Clouds: Rescaffolding the Megagenome of Sugar Pine (Pinus lambertiana) | Emerging Research in Plant Cell Biology | Scoop.it
We investigate the utility and scalability of new read cloud technologies to improve the draft genome assemblies of the colossal, and largely repetitive, genomes of conifers. Synthetic long read technologies have existed in various forms as a means of reducing complexity and resolving repeats since the outset of genome assembly. Recently, technologies that combine subhaploid pools of high molecular weight DNA with barcoding on a massive scale have brought new efficiencies to sample preparation and data generation. When combined with inexpensive light shotgun sequencing, the resulting data can be used to scaffold large genomes. The protocol is efficient enough to consider routinely for even the largest genomes. Conifers represent the largest reference genome projects executed to date. The largest of these is that of the conifer Pinus lambertiana (sugar pine), with a genome size of 31 billion bp. In this paper, we report on the molecular and computational protocols for scaffolding the P. lambertiana genome using the library technology from 10× Genomics. At 247,000 bp, the NG50 of the existing reference sequence is the highest scaffold contiguity among the currently published conifer assemblies; this new assembly’s NG50 is 1.94 million bp, an eightfold increase.
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Current Biology: Plant Autoimmunity: When Good Things Go Bad (2017)

Current Biology: Plant Autoimmunity: When Good Things Go Bad (2017) | Emerging Research in Plant Cell Biology | Scoop.it

A recent study finds that the Arabidopsis DM1 and DM2d proteins physically interact and trigger autoimmunity in plants. The DM1–DM2d interaction pattern differs from that of known immune receptor pairs, portraying the versatility in NLR functioning.

 

See Tran et al. Activation of a Plant NLR Complex through Heteromeric Association with an Autoimmune Risk Variant of Another NLR http://www.cell.com/current-biology/abstract/S0960-9822(17)30287-7


Via Kamoun Lab @ TSL
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A new proteinaceous pathogen‐associated molecular pattern (PAMP) identified in Ascomycete fungi induces cell death in Solanaceae

A new proteinaceous pathogen‐associated molecular pattern (PAMP) identified in Ascomycete fungi induces cell death in Solanaceae | Emerging Research in Plant Cell Biology | Scoop.it
Pathogen-associated molecular patterns (PAMPs) are detected by plant pattern recognition receptors (PRRs), which gives rise to PAMP-triggered immunity (PTI). We characterized a novel fungal PAMP, Cell Death Inducing 1 (RcCDI1), identified in the Rhynchosporium commune transcriptome sampled at an early stage of barley (Hordeum vulgare) infection.
The ability of RcCDI1 and its homologues from different fungal species to induce cell death in Nicotiana benthamiana was tested following agroinfiltration or infiltration of recombinant proteins produced by Pichia pastoris. Virus-induced gene silencing (VIGS) and transient expression of Phytophthora infestans effectors PiAVR3a and PexRD2 were used to assess the involvement of known components of PTI in N. benthamiana responses to RcCDI1.
RcCDI1 was highly upregulated early during barley colonization with R. commune. RcCDI1 and its homologues from different fungal species, including Zymoseptoria tritici, Magnaporthe oryzae and Neurospora crassa, exhibited PAMP activity, inducing cell death in Solanaceae but not in other families of dicots or monocots. RcCDI1-triggered cell death was shown to require N. benthamiana Brassinosteroid insensitive 1-Associated Kinase 1 (NbBAK1), N. benthamiana suppressor of BIR1-1 (NbSOBIR1) and N. benthamiana SGT1 (NbSGT1), but was not suppressed by PiAVR3a or PexRD2.
We report the identification of a novel Ascomycete PAMP, RcCDI1, recognized by Solanaceae but not by monocots, which activates cell death through a pathway that is distinct from that triggered by the oomycete PAMP INF1.

Via Steve Marek
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Nodule cysteine-rich peptides maintain a working balance during nitrogen-fixing symbiosis

Nodule cysteine-rich peptides maintain a working balance during nitrogen-fixing symbiosis | Emerging Research in Plant Cell Biology | Scoop.it
The nitrogen-fixing symbiosis between legumes and rhizobia is highly relevant to human society and global ecology. One recent breakthrough in understanding the molecular interplay between the plant and the prokaryotic partner is that, at least in certain legumes, the host deploys a number of antimicrobial peptides, called nodule cysteine-rich (NCR) peptides, to control the outcome of this symbiosis. Under this plant dominance, the bacteria are subject to the sub-lethal toxicity of these antimicrobial peptides, resulting in limited reproductive potential. However, recent genetic studies have added unexpected twists to this mechanism: certain NCR peptides are essential for the bacteria to adapt to the intracellular environment needed for a successful symbiosis, and the absence of these peptides can break down the mutualism. Meanwhile, some rhizobial strains have evolved a peptidase to specifically degrade these antimicrobial peptides, allowing the bacteria to escape host control. These findings challenge the preconceptions about ‘antimicrobial’ peptides, supporting the notion that their role in biotic interactions extends beyond toxicity to the microbial partners.

Via Christophe Jacquet
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The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis

The Tea Tree Genome Provides Insights into Tea Flavor and Independent Evolution of Caffeine Biosynthesis | Emerging Research in Plant Cell Biology | Scoop.it
Tea is the oldest and most popular caffeine-containing beverage in the world, being
consumed by more than 3 billion people across 160 countries. We report the first high-quality
genome of the tea tree Camellia sinensis var. assamica. Our comparative genomic, transcriptomic,
and phytochemical analyses gain novel insights into tea tree biology with an emphasis
on flavor and processing suitability of tea, and global adaptation of tea tree.
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African genomes illuminate the early history and transition to selfing in Arabidopsis thaliana

African genomes illuminate the early history and transition to selfing in Arabidopsis thaliana | Emerging Research in Plant Cell Biology | Scoop.it

Over the past 20 y, many studies have examined the history of the plant ecological and molecular model, Arabidopsis thaliana, in Europe and North America. Although these studies informed us about the recent history of the species, the early history has remained elusive. In a large-scale genomic analysis of African A. thaliana, we sequenced the genomes of 78 modern and herbarium samples from Africa and analyzed these together with over 1,000 previously sequenced Eurasian samples. In striking contrast to expectations, we find that all African individuals sampled are native to this continent, including those from sub-Saharan Africa. Moreover, we show that Africa harbors the greatest variation and represents the deepest history in the A. thaliana lineage. Our results also reveal evidence that selfing, a major defining characteristic of the species, evolved in a single geographic region, best represented today within Africa. Demographic inference supports a model in which the ancestral A. thaliana population began to split by 120–90 kya, during the last interglacial and Abbassia pluvial, and Eurasian populations subsequently separated from one another at around 40 kya. This bears striking similarities to the patterns observed for diverse species, including humans, implying a key role for climatic events during interglacial and pluvial periods in shaping the histories and current distributions of a wide range of species.

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