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The HEM Lines: A New Library of Homozygous Arabidopsis thaliana EMS Mutants and its Potential to Detect Meiotic Phenotypes. - Front Plant Sci. 2018 Sep 19

The HEM Lines: A New Library of Homozygous Arabidopsis thaliana EMS Mutants and its Potential to Detect Meiotic Phenotypes. - Front Plant Sci. 2018 Sep 19 | Publications @IJPB | Scoop.it

Genetic screens have been crucial for deciphering many important biological processes, including meiosis. In Arabidopsis thaliana, previous forward screens have likely identified almost all the meiotic genes that when mutated lead to a pronounced decrease in fertility. However, the increasing number of genes identified in reverse genetics studies that play crucial roles in meiosis, but do not exhibit strong phenotypes when mutated, suggests that there are still many genes with meiotic function waiting to be discovered. In this study, we produced 897 A. thaliana homozygous mutant lines using Ethyl Methyl Sulfonate (EMS) mutagenesis followed by either single seed descent or haploid doubling. Whole genome sequencing of a subset of lines showed an average of 696 homozygous mutations per line, 195 of which (28%) modify a protein sequence. To test the power of this library, we carried out a forward screen looking for meiotic defects by observing chromosomes at metaphase I of male meiosis. Among the 649 lines analyzed, we identified 43 lines with meiotic defects. Of these, 21 lines had an obvious candidate causal mutation, namely a STOP or splicing site mutation in a gene previously shown to play a role in meiosis (ATM, MLH3, MLH1, MER3, HEI10, FLIP, ASY4, FLIP, PRD2, REC8, FANCL, and PSS1). Interestingly, this was the first time that six of these genes were identified in a forward screen in Arabidopsis (MLH3, MLH1, SGO1, PSS1, FANCL, and ASY4). These results illustrate the potential of this mutant population for screening for any qualitative or quantitative phenotype. Thus, this new mutant library is a powerful tool for functional genomics in A. thaliana. The HEM (Homozygote EMS Mutants) lines are available at the Versailles Arabidopsis stock center.

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MEIOME IJPB team

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NPR1 mediates a novel regulatory pathway in cold acclimation by interacting with HSFA1 factors. Nature Plants. 24 sept. 2018 

NPR1 mediates a novel regulatory pathway in cold acclimation by interacting with HSFA1 factors. Nature Plants. 24 sept. 2018  | Publications @IJPB | Scoop.it

NON-EXPRESSER OF PATHOGENESIS-RELATED GENES 1 (NPR1) is a master regulator of plant response to pathogens that confers immunity through a transcriptional cascade mediated by salicylic acid and TGA transcription factors. Little is known, however, about its implication in plant response to abiotic stress. Here, we provide genetic and molecular evidence supporting the fact that Arabidopsis NPR1 plays an essential role in cold acclimation by regulating cold-induced gene expression independently of salicylic acid and TGA factors. Our results demonstrate that, in response to low temperature, cytoplasmic NPR1 oligomers release monomers that translocate to the nucleus where they interact with heat shock transcription factor 1 (HSFA1) to promote the induction of HSFA1-regulated genes and cold acclimation. These findings unveil an unexpected function for NPR1 in plant response to low temperature, reveal a new regulatory pathway for cold acclimation mediated by NPR1 and HSFA1 factors, and place NPR1 as a central hub integrating cold and pathogen signalling for a better adaptation of plants to an ever-changing environment.

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AGG IJPB team

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Evidence for the control of Arabidopsis gynoecium morphogenesis by ETTIN via cell wall dynamics - Plant Physiol. - 2018 Sep 20

Evidence for the control of Arabidopsis gynoecium morphogenesis by ETTIN via cell wall dynamics - Plant Physiol. - 2018 Sep 20 | Publications @IJPB | Scoop.it
ETTIN is an atypical member of the AUXIN RESPONSE FACTOR family of transcription factors, which plays a crucial role in tissue patterning in the Arabidopsis thaliana gynoecium. Though recent insights have provided valuable information on ETT's interactions with other components of auxin signaling, the biophysical mechanisms linking ETT to its ultimate effects on gynoecium morphology were until now unknown. Here, using techniques to assess cell-wall dynamics during gynoecium growth and development, we provide a coherent body of evidence to support a model in which ETT controls the elongation of the valves tissues of the gynoecium through the positive regulation of pectin methylesterase (PME) activity in the cell wall. This increase in PME activity results in an increase in the level of demethylesterified pectins and a consequent reduction in cell wall stiffness, leading to elongation of the valves. Though similar biophysical mechanisms have been shown to act in the stem apical meristem, leading to the expansion of organ primordia, our findings represent a new case in which the regulation of cell-wall stiffness through the covalent modification of pectin has been shown to contribute to tissue patterning within a developing plant organ.
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ACCI IJPB team

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Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids - New Phytologist - 16 September 2018

Parental transposable element loads influence their dynamics in young Nicotiana hybrids and allotetraploids - New Phytologist - 16 September 2018 | Publications @IJPB | Scoop.it

The genomic shock hypothesis suggests that allopolyploidy is associated with genome changes driven by transposable elements, as a response to imbalances between parental insertion loads. To explore this hypothesis, we compared three allotetraploids Nicotiana arentsii, N. rustica and N. tabacum, which arose over comparable time frames from hybridization between increasingly divergent diploid species.

We used sequence‐specific amplification polymorphism (SSAP) to compare the dynamics of six transposable elements in these allopolyploids, their diploid progenitors, and in corresponding synthetic hybrids.

We show that element‐specific dynamics in young Nicotiana allopolyploids reflect their dynamics in diploid progenitors. Transposable element mobilization is not concomitant with immediate genome merger, but occurs within the first generations of allopolyploid formation. In natural allopolyploids, such mobilizations correlate with imbalances in the repeat profile of the parental species, which increases with their genetic divergence. Other restructuring leading to locus loss is immediate, non‐random, and targeted at specific subgenomes, independently of cross orientation.

The correlation between transposable element mobilization in allopolyploids and quantitative imbalances in parental transposable element loads supports the genome shock hypothesis proposed by McClintock.

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RETROS IJPB team

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Labeling Maize (Zea mays L.) Leaves with 15 NH4+ and Monitoring Nitrogen Incorporation into Amino Acids by GC/MS Analysis - Curr Protoc Plant Biol. 2018 Sep 3

www.ncbi.nlm.nih.gov/pubmed/30198634

The human body contains approximately 3.2% nitrogen (N), mainly present as protein and amino acids. Although N exists at a high concentration (78%) in the air, it is not readily available to animals and most plants. Plants are however able to take up both nitrate (NO3- ) and ammonium (NH4+ ) ions from the soil and convert them to amino acids and proteins, which are excellent sources for all animals. Most N is available as the stable isotope 14 N, but a second form, 15 N, is present in very low concentrations. 15 N can be detected in extracts of plants by gas chromatography followed by mass spectrometry (GC/MS). In this protocol, the methods are described for tracing the pathway by which plants are able to take up 15 N-labeled nitrate and ammonium and convert them into amino acids and proteins. A protocol for extracting and quantifying amino acids and 15 N enrichment in maize (Zea mays L.) leaves labeled with 15 NH4+ is described. Following amino acid extraction, purification, and separation by GC/MS, a calculation of the 15 N enrichment of each amino acid is carried out on a relative basis to identify any differences in the dynamics of amino acid accumulation. This will allow a study of the impact of genetic modifications or mutations on key reactions involved in primary nitrogen and carbon metabolism.

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GAPV IJPB team

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RNAi‐suppression of barley caffeic acid O‐methyltransferase modifies lignin despite redundancy in the gene family - Plant Biotechnology Journal - 2018 Aug 22

RNAi‐suppression of barley caffeic acid O‐methyltransferase modifies lignin despite redundancy in the gene family - Plant Biotechnology Journal - 2018 Aug 22 | Publications @IJPB | Scoop.it

Caffeic acid O-methyltransferase (COMT), the lignin biosynthesis gene modified in many brown-midrib high-digestibility mutants of maize and sorghum, was targeted for downregulation in the small grain temperate cereal, barley (Hordeum vulgare), to improve straw properties. Phylogenetic and expression analyses identified the barley COMT orthologue(s) expressed in stems, defining a larger gene family than in brachypodium or rice with three COMT genes expressed in lignifying tissues. RNAi significantly reduced stem COMT protein and enzyme activity, and modestly reduced stem lignin content while dramatically changing lignin structure. Lignin syringyl-to-guaiacyl ratio was reduced by ~50%, the 5-hydroxyguaiacyl (5-OH-G) unit incorporated into lignin at 10-15-fold higher levels than normal, and the amount of p-coumaric acid ester-linked to cell walls was reduced by ~50%. No brown-midrib phenotype was observed in any RNAi line despite significant COMT suppression and altered lignin. The novel COMT gene family structure in barley highlights the dynamic nature of grass genomes. Redundancy in barley COMTs may explain the absence of brown-midrib mutants in barley and wheat. The barley COMT RNAi lines nevertheless have the potential to be exploited for bioenergy applications and as animal feed.

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IJPB team

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PUX10 associates with CDC48A and regulates the dislocation of ubiquitinated oleosins from seed lipid droplets - Plant Cell, 2018 Aug 7

PUX10 associates with CDC48A and regulates the dislocation of ubiquitinated oleosins from seed lipid droplets - Plant Cell, 2018 Aug 7 | Publications @IJPB | Scoop.it
Post-germinative mobilization of neutral lipids stored in seed lipid droplets (LDs) is preceded by the degradation of oleosins, the major structural LD proteins that stabilize LDs in dry seeds. We previously showed that Arabidopsis thaliana oleosins are marked for degradation by ubiquitination, and extracted from LDs before proteolysis. However, the mechanisms underlying the dislocation of these LD-anchored proteins from the LD monolayer are yet unknown. Here, we report that PUX10, a member of the plant UBX-domain containing (PUX) protein family, is an integral LD protein that associates with a subpopulation of LDs during seed germination. In pux10 mutant seedlings, PUX10 deficiency impaired the degradation of ubiquitinated oleosins, and prevented the extraction of ubiquitinated oleosins from LDs. We also showed that PUX10 interacts with ubiquitin and CDC48A, the AAA ATPase Cell Division Cycle 48, through its UBA and UBX domains, respectively. Collectively, these results strongly suggest that PUX10 is an adaptor recruiting CDC48A to ubiquitinated oleosins, thus facilitating the dislocation of oleosins from LDs by the segregase activity of CDC48A. We propose that PUX10 and CDC48A are core components of a LD-associated degradation machinery, which we named the LD-associated degradation (LDAD) system. Importantly, PUX10 is also the first determinant of a LD subpopulation described in plants, suggesting functional differentiation of LDs in Arabidopsis seedlings.
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SPACE & DIPOL & DYSCOL IJPB teams

 

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A spatiotemporal DNA endoploidy map of the Arabidopsis root reveals roles for the endocycle in root development and stress adaptation - Plant Cell. 2018 Aug 16

A spatiotemporal DNA endoploidy map of the Arabidopsis root reveals roles for the endocycle in root development and stress adaptation - Plant Cell. 2018 Aug 16 | Publications @IJPB | Scoop.it
Somatic polyploidy caused by endoreplication is observed in arthropods, molluscs, and vertebrates, but is especially prominent in higher plants where it has been postulated to be essential for cell growth and fate maintenance. However, a comprehensive understanding of the physiological significance of plant endopolyploidy has remained elusive. Here, we modeled and experimentally verified a high-resolution DNA endoploidy map of the developing Arabidopsis thaliana root, revealing a remarkable spatiotemporal control of DNA endoploidy levels across tissues. Fitting of a simplified model to publicly available datasets profiling root gene expression under various environmental stress conditions suggested that this root endoploidy patterning may be stress-responsive. Furthermore, cellular and transcriptomic analyses revealed that inhibition of endoreplication onset alters the nuclear-to-cellular volume ratio and the expression of cell wall modifying genes, in correlation with the appearance of cell structural changes. Our data indicate that endopolyploidy might serve to coordinate cell expansion with structural stability, and that spatiotemporal endoreplication pattern changes may buffer for stress conditions, which may explain the widespread occurrence of the endocycle in plant species growing in extreme or variable environments.
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PAR IJPB team -

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The wheat TdRL1 is the functional homolog of the rice RSS1 and promotes plant salt stress tolerance - Plant Cell Rep. 2018 Aug 11

The wheat TdRL1 is the functional homolog of the rice RSS1 and promotes plant salt stress tolerance - Plant Cell Rep. 2018 Aug 11 | Publications @IJPB | Scoop.it

Key message Rice rss1 complementation assays show that wheat TdRL1 and RSS1 are true functional homologs. TdRL1 over-expression in Arabidopsisconferred salt stress tolerance and alleviated ROS

www.ncbi.nlm.nih.gov/pubmed/30099611/

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BCR IJPB Team

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Seed coats as an alternative molecular factory: thinking outside the box. Plant Reprod. 2018 Jul 28

Seed coats as an alternative molecular factory: thinking outside the box. Plant Reprod. 2018 Jul 28 | Publications @IJPB | Scoop.it

Seed coats as commodities. Seed coats play important roles in the protection of the embryo from biological attack and physical damage by the environment as well as dispersion strategies. A significant part of the energy devoted by the mother plant to seed production is channeled into the production of the cell layers and metabolites that surround the embryo. Nevertheless, in crop species these are often discarded post-harvest and are a wasted resource that could be processed to yield co-products. The production of novel compounds from existing metabolites is also a possibility. A number of macromolecules are already accumulated in these maternal layers that could be exploited in industrial applications either directly or via green chemistry, notably flavonoids, lignin, lignan, polysaccharides, lipid polyesters and waxes. Here, we summarize our knowledge of the in planta biosynthesis pathways of these macromolecules and their molecular regulation as well as potential applications. We also outline recent work aimed at providing further tools for increasing yields of existing molecules or the development of novel biotech approaches, as well as trial studies aimed at exploiting this underused resource.

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PHYGERM-IJPB team

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Identification of ASYNAPTIC4, a component of the meiotic chromosome axis. Plant Physiol. 2018 Jul 12

Identification of ASYNAPTIC4, a component of the meiotic chromosome axis. Plant Physiol. 2018 Jul 12 | Publications @IJPB | Scoop.it

During the leptotene stage of prophase I of meiosis, chromatids become organized into a linear looped array via a protein axis that forms along the loop bases. Establishment of the axis is essential for the subsequent synapsis of the homologous chromosome pairs and the progression of recombination to form genetic crossovers. Here, we describe ASYNAPTIC4 (ASY4), a meiotic axis protein in Arabidopsis thaliana. ASY4 is a small coiled-coil protein that exhibits limited sequence similarity with the C-terminal region of the axis protein ASY3. We used enhanced yellow fluorescent protein (eYFP)-tagged ASY4 to show that ASY4 localizes to the chromosome axis throughout prophase I. Bi-molecular fluorescence complementation revealed that ASY4 interacts with ASY1 and ASY3, and yeast two-hybrid analysis confirmed a direct interaction between ASY4 and ASY3. Mutants lacking full-length ASY4 exhibited defective axis formation and were unable to complete synapsis. Although initiation of recombination appeared to be unaffected in the asy4 mutant, the number of crossovers was significantly reduced and crossovers tended to group in the distal parts of the chromosomes. We conclude that ASY4 is required for normal axis and crossover formation. Furthermore, our data suggest that ASY3/ASY4 are the functional homologues of the mammalian SYCP2/SYCP3 axial components.

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SAG12, a major cysteine protease involved in nitrogen mobilization during senescence for seed production in Arabidopsis thaliana. - Plant Cell Physiol. 2018 Jul 3.

SAG12, a major cysteine protease involved in nitrogen mobilization during senescence for seed production in Arabidopsis thaliana. - Plant Cell Physiol. 2018 Jul 3. | Publications @IJPB | Scoop.it

SAG12 is the most widely used senescence-associated reference gene for characterizing leaf senescence, and the increase in SAG12 protein during leaf senescence is remarkable. However, the role of this cysteine protease in N remobilization and the leaf senescence process remains unclear. The role of SAG12 has been poorly investigated and the few reports dealing with this are somewhat controversial. Indeed, sag12 Arabidopsis mutants have not shown any phenotype while OsSAG12-1 and OsSAG12-2 overexpression in rice moderates senescence progression. Therefore, this study aims at clarifying the role of the SAG12 cysteine protease during the entire plant lifespan and during leaf senescence. Arabidopsis thaliana plants knocked-out for the SAG12 gene (sag12) did not exhibit any special phenotypic traits when grown under optimal nitrogen supply (HN), suggesting that other cysteine proteases could provide compensatory effects. Moreover, for the first time, this study shows that aspartate protease activity is significantly increased in sag12. Among the putative aspartate proteases involved, a CND41-like aspartate protease has been identified. Under low nitrogen (LN) availability, when inducible proteolytic systems are not sufficient to cope with SAG12 depletion, a decrease in yield is observed. Altogether, these results show that SAG12 (and perhaps also aspartate proteases) could be involved in RuBisCO degradation during the leaf senescence associated with seed filling.

Plant Cell Physiol. 2018 Jul 3. doi: 10.1093/pcp/pcy125.

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IJPB SATURNE team

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Seed Evolution, A 'Simpler' Story. - Trends Plant Sci. 2018 Jun 27

Seed Evolution, A 'Simpler' Story. - Trends Plant Sci. 2018 Jun 27 | Publications @IJPB | Scoop.it

Seed evolution is often presented as the evolution of morphological complexity. Following the steps of Wilhelm Hofmeister, I argue that changes in the development of one tissue, the megasporangium/nucellus, can explain the origin of the seed habit. Here, I lay down a 'simpler' story that correlates seed evolution to nucellus cell fate.

Trends Plant Sci. 2018 Jun 27. pii: S1360-1385(18)30131-6. doi: 10.1016/j.tplants.2018.06.002.

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Natural variation at XND1 impacts root hydraulics and trade-off for stress responses in Arabidopsis. Nat Commun. 2018 Sep

Natural variation at XND1 impacts root hydraulics and trade-off for stress responses in Arabidopsis. Nat Commun. 2018 Sep | Publications @IJPB | Scoop.it

Soil water uptake by roots is a key component of plant performance and adaptation to adverse environments. Here, we use a genome-wide association analysis to identify the XYLEM NAC DOMAIN 1 (XND1) transcription factor as a negative regulator of Arabidopsis root hydraulic conductivity (Lpr). The distinct functionalities of a series of natural XND1 variants and a single nucleotide polymorphism that determines XND1 translation efficiency demonstrate the significance of XND1 natural variation at species-wide level. Phenotyping of xnd1 mutants and natural XND1 variants show that XND1 modulates Lpr through action on xylem formation and potential indirect effects on aquaporin function and that it diminishes drought stress tolerance. XND1 also mediates the inhibition of xylem formation by the bacterial elicitor flagellin and counteracts plant infection by the root pathogen Ralstonia solanacearum. Thus, genetic variation at XND1, and xylem differentiation contribute to resolving the major trade-off between abiotic and biotic stress resistance in Arabidopsis

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VAST IJPB team

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Emerging Functions for Cell Wall Polysaccharides Accumulated during Eudicot Seed Development. - Plants (Basel) 2018 Sep 29

Emerging Functions for Cell Wall Polysaccharides Accumulated during Eudicot Seed Development. - Plants (Basel) 2018 Sep 29 | Publications @IJPB | Scoop.it

The formation of seeds is a reproductive strategy in higher plants that enables the dispersal of offspring through time and space. Eudicot seeds comprise three main components, the embryo, the endosperm and the seed coat, where the coordinated development of each is important for the correct formation of the mature seed. In addition, the seed coat protects the quiescent progeny and can provide transport mechanisms. A key underlying process in the production of seed tissues is the formation of an extracellular matrix termed the cell wall, which is well known for its essential function in cytokinesis, directional growth and morphogenesis. The cell wall is composed of a macromolecular network of polymers where the major component is polysaccharides. The attributes of polysaccharides differ with their composition and charge, which enables dynamic remodeling of the mechanical and physical properties of the matrix by adjusting their production, modification or turnover. Accordingly, the importance of specific polysaccharides or modifications is increasingly being associated with specialized functions within seed tissues, often through the spatio-temporal accumulation or remodeling of particular polymers. Here, we review the evolution and accumulation of polysaccharides during eudicot seed development, what is known of their impact on wall architecture and the diverse roles associated with these in different seed tissues.

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PHYGERM IJPB team

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Sphingobacterium sp. T2 manganese superoxide dismutase catalyses the oxidative demethylation of polymeric lignin via generation of hydroxyl radical - ACS Chemical Biology - September 24, 2018

Sphingobacterium sp. T2 contains two extracellular manganese superoxide dismutase enzymes which exhibit unprecedented activity for lignin oxidation, but via an unknown mechanism. Enzymatic treatment of lignin model compounds gave products whose structures were indicative of aryl-C oxidative cleavage and demethylation, as well as alkene dihydroxylation and alcohol oxidation. 18O labelling studies on the SpMnSOD-catalysed oxidation of lignin model compound guiaiacylglycerol--guaiacyl ether indicated that the oxygen atom inserted by the enzyme is derived from superoxide or peroxide. Analysis of an alkali lignin treated by SpMnSOD1 by quantitative 31P NMR spectroscopy demonstrated 20-40% increases in phenolic and aliphatic OH content, consistent with lignin demethylation and some internal oxidative cleavage reactions. Assay for hydroxyl radical generation using a fluorometric hydroxyphenylfluorescein assay revealed the release of approximately 1 molar equivalent of hydroxyl radical by SpMnSOD1. Four amino acid replacements in SpMnSOD1 were investigated, and A31H or Y27H site-directed mutant enzymes were found to show no lignin demethylation activity according to 31P NMR analysis. Structure determination of the A31H and Y27H mutant enzymes reveals the repositioning of an N-terminal protein loop, leading to widening of a solvent channel at the dimer interface, which would provide increased solvent access to the Mn centre for hydroxyl radical generation.

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IJPB team Apsynth

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Increasing medium chain fatty acids production in Yarrowia lipolytica by metabolic engineering - Microbial Cell Factories - 2018 Sep 10

Increasing medium chain fatty acids production in Yarrowia lipolytica by metabolic engineering - Microbial Cell Factories - 2018 Sep 10 | Publications @IJPB | Scoop.it

Oleaginous yeast Yarrowia lipolytica is an organism of choice for the development of biofuel and oleochemicals. It has become a chassis for metabolic engineering in order to produce targeted lipids. Understanding the function of key-enzymes involved in lipid metabolism is essential to design better routes for enhanced lipid production and for strains producing lipids of interest. Because medium chain fatty acids (MCFA) are valuable compounds for biokerosene production, we previously generated strains capable of producing MCFA up to 12% of total lipid content (Rigouin et al. in ACS Synth Biol 6:1870–1879, 2017). In order to improve accumulation and content of C14 fatty acid (FA), the elongation, degradation and accumulation of these MCFA in Yarrowia lipolytica were studied. We brought evidence of the role of YALI0F0654 (YlELO1) protein in the elongation of exogenous or de novo synthesized C14 FA into C16 FA and C18 FA. YlELO1 deletion into a αFAS_I1220W expressing strain leads to the sole production of C14 FA. However, because this strain does not provide the FA essential for its growth, it requires being cultivated with essential fatty acids and C14 FA yield is limited. To promote MCFA accumulation in Y. lipolytica without compromising the growth, we overexpressed a plant diglyceride acyltransferase specific for MCFA and reached an accumulation of MCFA up to 45% of total lipid content. We characterized the role of YlELO1 in Y. lipolytica by proving its involvement in Medium chain fatty acids elongation. We showed that MCFA content can be increased in Yarrowia lipolytica by promoting their accumulation into a stable storage form (triacylglycerides) to limit their elongation and their degradation.

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Control of adventitious root formation: Insights into synergistic and antagonistic hormonal interactions - Physiologia Plantarum - 2018 Aug 29

Control of adventitious root formation: Insights into synergistic and antagonistic hormonal interactions - Physiologia Plantarum - 2018 Aug 29 | Publications @IJPB | Scoop.it

Plants have evolved sophisticated root systems that help them to cope with harsh environmental conditions. They are typically composed of a primary root (PR) and lateral roots (LRs), but may also include adventitious roots (ARs). Unlike LRs, ARs may be initiated not only from pericycle cells, but from various cell types and tissues depending on the species. Phytohormones, together with many other internal and external stimuli, coordinate and guide every step of AR formation from the first event of cell reprogramming until emergence and outgrowth. In this review we summarize recent advances in the molecular mechanisms controlling AR formation and highlight the main hormonal cross‐talk involved in its regulation under different conditions and in different model systems.

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PATS IJPB team

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A regulatory role of autophagy for resetting the memory of heat stress in plants - Plant, Cell & Environment - 2018 Aug 22

A regulatory role of autophagy for resetting the memory of heat stress in plants - Plant, Cell & Environment - 2018 Aug 22 | Publications @IJPB | Scoop.it
As sessile life forms, plants are repeatedly confronted with adverse environmental conditions, which can impair development, growth and reproduction. During evolution, plants have established mechanisms to orchestrate the delicate balance between growth and stress tolerance, to reset cellular biochemistry once stress vanishes, or to keep a molecular memory, which enables survival of a harsher stress that may arise later. Although there are several examples of memory in diverse plants species, the molecular machinery underlying the formation, duration and resetting of stress memories is largely unknown so far. We report here that autophagy, a central self-degradative process, assists in resetting cellular memory of heat stress (HS) in Arabidopsis thaliana. Autophagy is induced by thermopriming (moderate HS) and, intriguingly, remains high long after stress termination. We demonstrate that autophagy mediates the specific degradation of heat shock proteins (HSPs) at later stages of the thermorecovery phase leading to the accumulation of protein aggregates after the second HS and a compromised heat tolerance. Autophagy mutants retain HSPs longer than wild type and concomitantly display improved thermomemory. Our findings reveal a novel regulatory mechanism for HS memory in plants.
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One Way to Achieve Germination: Common Molecular Mechanism Induced by Ethylene and After-Ripening in Sunflower Seeds - Int J Mol Sci. 2018 Aug 20

One Way to Achieve Germination: Common Molecular Mechanism Induced by Ethylene and After-Ripening in Sunflower Seeds - Int J Mol Sci. 2018 Aug 20 | Publications @IJPB | Scoop.it
Dormancy is an adaptive trait that blocks seed germination until the environmental conditions become favorable for subsequent vegetative plant growth. Seed dormancy is defined as the inability to germinate in favorable conditions. Dormancy is alleviated during after-ripening, a dry storage period, during which dormant (D) seeds unable to germinate become non-dormant (ND), able to germinate in a wide range of environmental conditions. The treatment of dormant seeds with ethylene (D/ET) promotes seed germination, and abscisic acid (ABA) treatment reduces non-dormant (ND/ABA) seed germination in sunflowers (Helianthus annuus). Metabolomic and transcriptomic studies have been performed during imbibition to compare germinating seeds (ND and D/ET) and low-germinating seeds (D and ND/ABA). A PCA analysis of the metabolites content showed that imbibition did not trigger a significant change during the first hours (3 and 15 h). The metabolic changes associated with germination capacity occurred at 24 h and were related to hexoses, as their content was higher in ND and D/ET and was reduced by ABA treatment. At the transcriptional level, a large number of genes were altered oppositely in germinating, compared to the low-germinating seeds. The metabolomic and transcriptomic results were integrated in the interpretation of the processes involved in germination. Our results show that ethylene treatment triggers molecular changes comparable to that of after-ripening treatment, concerning sugar metabolism and ABA signaling inhibition.
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PHYGERM - IJPB team

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Allele specific expression and genetic determinants of transcriptomic variations in response to mild water deficit in tomato - Plant J. 2018 Aug 6

Allele specific expression and genetic determinants of transcriptomic variations in response to mild water deficit in tomato - Plant J. 2018 Aug 6 | Publications @IJPB | Scoop.it

Characterizing the natural diversity of gene expression across environments is an important step in understanding how genotype by environment interactions shape phenotypes. Here, we analyzed the impact of water deficit onto gene expression levels in tomato at the genome-wide scale. We sequenced the transcriptome of growing leaves and fruit pericarps at cell expansion stage in a cherry and a large fruited accession and their F1 hybrid grown under two watering regimes. Gene expression levels were steadily affected by the genotype and the watering regime. Whereas phenotypes showed mostly additive inheritance, ~80% of the genes displayed non-additive inheritance. By comparing allele specific expression in the F1 hybrid to the allelic expression in both parental lines, respectively, 3,005 genes in leaf and 2,857 genes in fruit deviated from 1:1 ratio independently of the watering regime. Among these genes, ~55% were controlled by cis factors, ~25% by trans factors and ~20% by a combination of both types. A total of 328 genes in leaf and 113 in fruit exhibited significant allele specific expression by watering regime interaction, among which ~80% presented trans by watering regime interaction suggesting a response to water deficit mediated through a majority of trans acting loci in tomato. We cross-validated the expression levels of 274 transcripts in fruit and leaves of 124 RILs and identified 163 eQTLs mostly confirming the divergences identified by allele specific expression. Combining phenotypic and expression data, we observed a complex network of variation between genes encoding enzymes involved in the sugar metabolism.

www.ncbi.nlm.nih.gov/pubmed/30079488

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AGG IJPB Team

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Three New Pentatricopeptide Repeat Proteins Involved in Splicing of Mitochondrial transcripts and Complex I Biogenesis in Arabidopsis thaliana. J Exp Bot. 2018 Jul 25.

Three New Pentatricopeptide Repeat Proteins Involved in Splicing of Mitochondrial transcripts and Complex I Biogenesis in Arabidopsis thaliana. J Exp Bot. 2018 Jul 25. | Publications @IJPB | Scoop.it

Group Ⅱ introns are common features of most angiosperm mitochondrial genomes. Intron splicing is thus essential for the expression of mitochondrial genes and is facilitated by numerous nuclear-encoded proteins. However, the molecular mechanism and the protein cofactors involved in this complex process have not been fully elucidated. In this study, we characterized three new pentatricopeptide repeat (PPR) genes, called MISF26, MISF68 and MISF74, of Arabidopsis thaliana and showed they all function in group II intron splicing and plant development. The three PPR genes encode P-type PPR proteins that localize in the mitochondrion. Transcript analysis revealed that the splicing of a single intron is altered in misf26 mutants, while several mitochondrial intron splicing defects were detected in misf68 and misf74 mutants. To our knowledge, MISF68 and MISF74 are the first two PPR proteins implicated in the splicing of more than one intron in plant mitochondria, suggesting that they may facilitate splicing differently than other previously identified PPR splicing factors. The splicing defects in the misf mutants induce a significant decrease in complex I assembly and activity, and an over-expression of mRNAs of the alternative respiratory pathway. These results therefore reveal that nuclear encoded proteins MISF26, MISF68 and MISF74 are involved in splicing of a cohort of mitochondrial group II introns and thereby required for complex I biogenesis.

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ORGAREPRO - IJPB team

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Receptor Kinase THESEUS1 Is a Rapid Alkalinization Factor 34 Receptor in Arabidopsis. Current Biology; August 6, 2018

Receptor Kinase THESEUS1 Is a Rapid Alkalinization Factor 34 Receptor in Arabidopsis. Current Biology; August  6,  2018 | Publications @IJPB | Scoop.it

The growth of plants, like that of other walled organisms, depends on the ability of the cell wall to yield without losing its integrity. In this context, plant cells can sense the perturbation of their walls and trigger adaptive modifications in cell wall polymer interactions. Catharanthus roseus receptor-like kinase 1-like (CrRLK1L) THESEUS1 (THE1) was previously shown in Arabidopsis to trigger growth inhibition and defense responses upon perturbation of the cell wall, but so far, neither the ligand nor the role of the receptor in normal development was known. Here, we report that THE1 is a receptor for the peptide rapid alkalinization factor (RALF) 34 and that this signaling module has a role in the fine-tuning of lateral root initiation. We also show that RALF34-THE1 signaling depends, at least for some responses, on FERONIA (FER), another RALF receptor involved in a variety of processes, including immune signaling, mechanosensing, and reproduction. Together, the results show that RALF34 and THE1 are part of a signaling network that integrates information on the integrity of the cell wall with the coordination of normal morphogenesis.

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PAR-IJPB team

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Heterogeneity and its multiscale integration in plant morphogenesis. Curr Opin Plant Biol. 2018 Jul 13

Heterogeneity and its multiscale integration in plant morphogenesis. Curr Opin Plant Biol. 2018 Jul 13 | Publications @IJPB | Scoop.it

Heterogeneity is observed at all levels in living organisms, but its role during the development of an individual is not well understood. Heterogeneity has either to be limited to ensure robust development or can be an actor of the biological processes leading to reproducible development. Here we review the sources of heterogeneity in plants, stress the interplay between noise in elementary processes and regulated biological mechanisms, and highlight how heterogeneity is integrated at multiple scales during plant morphogenesis.

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FTA-IJPB team

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Getting leaves into shape: a molecular, cellular, environmental and evolutionary view, Development 10 July 2018

Getting leaves into shape: a molecular, cellular, environmental and evolutionary view, Development 10 July 2018 | Publications @IJPB | Scoop.it
Leaves arise from groups of undifferentiated cells as small primordia that go through overlapping phases of morphogenesis, growth and differentiation. These phases are genetically controlled and modulated by environmental cues to generate a stereotyped, yet plastic, mature organ. Over the past couple of decades, studies have revealed that hormonal signals, transcription factors and miRNAs play major roles during leaf development, and more recent findings have highlighted the contribution of mechanical signals to leaf growth. In this Review, we discuss how modulating the activity of some of these regulators can generate diverse leaf shapes during development, in response to a varying environment, or between species during evolution.

dev.biologists.org/content/145/13/dev161646

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FTA IJPB team

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