植物学人|20171017-陈晓亚院士发现调控棉花棉纤维新机制（推荐）

致谢：感谢中科院上海生科院的马同学提供了信息。

iNature：在植物学主流专刊中，主要有Plant Cell，Molecular Plant，Plant Journal，PLANT PHYSIOLOGY，NEW PHYTOLOGIST，Plant Biotech J，Plant Cell &Environ，Nature Plants等8种期刊。现在经过前期的测试，iNature决定每天遴选8大植物学主刊各1篇（福利版），共8篇文章，推送给大家，使大家能及时的了解植物学领域的动态：

Plant Cell:密歇根大学Thomashow等人揭示CAMTA介导的SA（茉莉酸）途径涉及低温及病原体感染的应答作用；

Nature Plants:剑桥大学Dupree等人揭示木质素与纤维素的相互作用对于植物的细胞壁合成至关重要；

Molecular Plant:乔治大学Schmitz发表综述揭示植物异染色质靶向特异性（尤其是DNA甲基化）；

Plant Journal:法国斯特拉斯堡大学Duchene等人揭示细胞核中的mRNA与细胞核的关系；

PLANT PHYSIOLOGY:日本理化研究所Seki揭示组蛋白去乙酰化酶在SA（茉莉酸）途径应答中的作用；

NEW PHYTOLOGIST:中科院上海生科院植生所陈晓亚等发现调控棉花棉纤维的MIXTA基因的遗传与进化机理；

Plant Biotech J:罗格斯大学Leustek等人揭示丝氨酸乙酰转移酶在玉米叶中的过表达增加了种子特异性甲硫氨酸富集的玉米素；

Plant Cell &Environ:悉尼技术大学Eamus等人揭示干旱期间渗透调节差异，叶面ABA动力学和异位和异羟基木本被子植物之间的气孔调节。

1Plant Cell：密歇根大学Thomashow等人揭示CAMTA介导的SA（茉莉酸）途径涉及低温及病原体感染的应答作用

Abstract

Arabidopsis thaliana Calmodulin-binding Transcription Activation (CAMTA) factors repress the expression of genes involved in salicylic acid (SA) biosynthesis and SA-mediated immunity in healthy plants grown at warm temperature (22°C). This repression is overcome in plants exposed to low temperature (4°C) for more than a week and in plants infected by biotrophic and hemibiotrophic pathogens. Here we present evidence that CAMTA3-mediated repression of SA pathway genes in non-stressed plants involves the action of an N-terminal repression module (NRM) that acts independently of calmodulin (CaM) binding to the IQ and CaM-binding (CaMB) domain, a finding that is contrary to current thinking that CAMTA3 repression activity requires binding of CaM to the CaMB domain. Induction of SA-pathway genes in response to low temperature did not occur in plants expressing only the CAMTA3-NRM region of the protein. Mutational analysis provided evidence that the repression activity of the NRM was suppressed by action of the IQ and CaMB domains responding to signals generated in response to low temperature. Plants expressing the CAMTA3-NRM region were also impaired in defense against the bacterial hemibiotrophic pathogen Pseudomonas syringae pv. tomato DC3000. Our results indicate that the regulation of CAMTA3 repression activity by low temperature and pathogen infection involves related mechanisms, but with distinct differences.

原文链接：

http://www.plantcell.org/content/early/2017/10/05/tpc.16.00865

2Nature Plants：剑桥大学Dupree等人揭示木质素与纤维素的相互作用对于植物的细胞壁合成至关重要

Abstract

Xylan and cellulose are abundant polysaccharides in vascular plants and essential for secondary cell wall strength. Acetate or glucuronic acid decorations are exclusively found on even-numbered residues in most of the glucuronoxylan polymer. It has been proposed that this even-specific positioning of the decorations might permit docking of xylan onto the hydrophilic face of a cellulose microfibril. Consequently, xylan adopts a flattened ribbon-like twofold screw conformation when bound to cellulose in the cell wall. Here we show that ESKIMO1/XOAT1/TBL29, a xylan-specific O-acetyltransferase, is necessary for generation of the even pattern of acetyl esters on xylan in Arabidopsis. The reduced acetylation in the esk1 mutant deregulates the position-specific activity of the xylan glucuronosyltransferase GUX1, and so the even pattern of glucuronic acid on the xylan is lost. Solid-state NMR of intact cell walls shows that, without the even-patterned xylan decorations, xylan does not interact normally with cellulose fibrils. We conclude that the even pattern of xylan substitutions seen across vascular plants enables the interaction of xylan with hydrophilic faces of cellulose fibrils, and is essential for development of normal plant secondary cell walls.

原文链接：

https://www.nature.com/articles/s41477-017-0030-8

3Molecular Plant：乔治大学Schmitz发表综述揭示植物异染色质靶向特异性（尤其是DNA甲基化）

Abstract

Plants encode a diverse repertoire of DNA methyltransferases that have specialized to target cytosines for methylation in specific sequence contexts. These include the de novo methyltransferase, DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM2), which methylates cytosines in all sequence contexts through an RNA guided process, the CHROMOMETHYLASES (CMTs), which methylate CHH and CHG cytosines (where H is A, T, or C), and the maintenance methyltransferase, METHYLTRANSFERASE 1 (MET1), which maintains methylation of symmetrical CG contexts. In this review, we discuss the sequence specificities and targeting of each of these pathways. In particular, we highlight recent studies that indicate CMTs preferentially target CWG or CWA/CAW motifs (where W is A or T), and summarize how self-reinforcing feedback loops between DNA methyltransferases and histone modifications characteristic of heterochromatin specify targeting. Finally, the initiating events that lead to gene body methylation are discussed as a model for how interdependent targeting of different silencing pathways can potentiate the establishment of off-target epialleles.

原文链接：

http://www.cell.com/molecular-plant/abstract/S1674-2052(17)30301-5

4Plant Journal：法国斯特拉斯堡大学Duchene等人揭示细胞核中的mRNA与细胞核的关系

Abstract

Intracellular sorting of mRNAs is an essential process to regulate gene expression and protein localization. Most of mitochondrial proteins are nuclear-encoded and imported into mitochondria, through post-translational or co-translational processes. In the latter case, mRNAs are found enriched in the vicinity of mitochondria. A genome-scale analysis of mRNAs associated with mitochondria has been performed to determine plant cytosolic mRNAs targeted to the mitochondrial surface. Many messengers encoding mitochondrial proteins were found associated with mitochondria. These mRNAs correspond to particular functions and complexes such as respiration or mitoribosomes, which indicates a coordinated control of mRNAs localization within metabolic pathways. In addition, upstream AUGs in 5′-UTR, which modulate translation efficiency of downstream sequences, were found to negatively affect mRNAs association with mitochondria. A mutational approach coupled with in vivo mRNA visualization confirmed this observation. Moreover, this technic allowed the identification of 3′-UTR as another essential element for mRNA localization at the mitochondrial surface. Therefore, this work offers new insights into the mechanism, function and regulation of cytosolic mRNAs association with plant mitochondria.

原文链接：

http://onlinelibrary.wiley.com/doi/10.1111/tpj.13749/full

5PLANT PHYSIOLOGY：日本理化研究所Seki揭示组蛋白去乙酰化酶在SA（茉莉酸）途径应答中的作用

Abstract

Histone acetylation is an essential process in the epigenetic regulation of diverse biological processes including environmental stress responses in plants. Previously, our research group identified a histone deacetylase (HDAC) inhibitor (HDI) that confers salt tolerance in Arabidopsis. In the present study, we demonstrate that class I HDAC (HDA19) and class II HDACs (HDA5/14/15/18) control responses to salt stress through different pathways. The screening of 12 different selective HDIs indicated that seven newly reported HDIs enhance salt tolerance. Genetic analysis, based on a pharmacological study, identified which HDACs function in salinity stress tolerance. In the wild-type Col-0 background, hda19 plants exhibit tolerance to high salinity stress, while hda5/14/15/18 plants exhibit hyper-sensitivity to salt stress. Transcriptome analysis revealed that the effect of HDA19-deficiency on the response to salinity stress is distinct from that of HDA5/14/15/18-deficiencies. In hda19 plants, the expression levels of stress-tolerance related genes; late embryogenesis abundant (LEA) proteins which prevent protein aggregation, and positive regulators such as ABI5 and NAC019 in ABA signaling, were strongly induced, relative to the wild-type. Neither of these elements were up-regulated in the hda5/14/15/18 plants. The mutagenesis of HDA19 by genome editing in the hda5/14/15/18 plants enhanced salt tolerance, suggesting that suppression of HDA19 masks the phenotype caused by that of class II HDACs in salinity stress response. Collectively, our results demonstrate that HDIs which inhibit class I HDACs allow the rescue of plants from salinity stress regardless of their selectivity, and provide insight into the hierarchal regulation of environmental stress responses through HDAC isoforms.

原文链接：

http://www.plantphysiol.org/content/early/2017/10/10/pp.17.01332

6NEW PHYTOLOGIST：中科院上海生科院植生所陈晓亚等发现调控棉花棉纤维的MIXTA基因的遗传与进化机理

Abstract

Cotton, withcellulose-enriched mature fibers, is the largest source of natural textiles. Througha map-based cloning strategy, we isolated an industrially important lint fiberdevelopment gene (Li3) that encodes an MYB-MIXTA-like transcription factor(MML) on chromosome D12 (GhMML4_D12). Virus-induced gene silencing ordecreasing the expression of the GhMML4_D12 gene in n2NSM plants resulted in asignificant reduction in epidermal cell prominence and lint fiber production.GhMML4_D12 is arranged in tandem with GhMML3, another MIXTA gene responsiblefor fuzz fiber development. These two very closely related MIXTA genes direct fiberinitiation production in two specialized cell forms: lint and fuzz fibers. Theymay control the same metabolic pathways in different cell types. The MIXTAsexpanded in Malvaceae during their evolution and produced a Malvaceaespecificfamily that regulates epidermal cell differentiation, different from the genefamily that regulates leaf hair trichome development. Cotton has developed aunique transcriptional regulatory network for fiber development.Characterization of target genes regulating fiber production has providedinsights into the molecular mechanisms underlying cotton fiber development andhas allowed the use of genetic engineering to increase lint yield by inducingmore epidermal cells to develop into lint rather than fuzz fibers.

原文链接：

http://onlinelibrary.wiley.com/doi/10.1111/nph.14844/full

7Plant Biotech J：罗格斯大学Leustek等人揭示丝氨酸乙酰转移酶在玉米叶中的过表达增加了种子特异性甲硫氨酸富集的玉米素

Abstract

Maize kernels do not contain enough of the essential sulfur-amino acid methionine (Met) to serve as a complete diet for animals, even though maize has the genetic capacity to store Met in kernels. Prior studies indicated that the availability of the sulfur (S)-amino acids may limit their incorporation into seed storage proteins. Serine acetyltransferase (SAT) is a key control point for S-assimilation leading to Cys and Met biosynthesis and SAT overexpression is known to enhance S-assimilation without negative impact on plant growth. Therefore, we overexpressed Arabidopsis thaliana AtSAT1 in maize under control of the leaf bundle-sheath-cell-specific rbcS1 promoter to determine the impact on seed storage protein expression. The transgenic events exhibited up to 12-fold higher SAT activity without negative impact on growth. S-assimilation was increased in the leaves of SAT overexpressing plants, followed by higher levels of storage protein mRNA and storage proteins, particularly the 10-kDa δ-zein, during endosperm development. This zein is known to impact the level of Met stored in kernels. The elite event with the highest expression of  AtSAT1  showed 1.40 fold increase in kernel Met. When fed to chickens, transgenic  AtSAT1 kernels significantly increased growth rate compared with the parent maize line. The result demonstrates the efficacy of increasing maize nutritional value by SAT overexpression without apparent yield loss. Maternal overexpression of SAT in vegetative tissues was necessary for high-Met zein accumulation. Moreover, SAT overcomes the shortage of S-amino acids that limits the expression and accumulation of high Met-zeins during kernel development.

原文链接：

http://onlinelibrary.wiley.com/doi/10.1111/pbi.12851/full

8Plant Cell &Environ：悉尼技术大学Eamus等人揭示干旱期间渗透调节差异，叶面ABA动力学和异位和异羟基木本被子植物之间的气孔调节

Abstract

Species are often classified along a continuum from isohydric to anisohydric, with isohydric species exhibiting tighter regulation of leaf water potential through stomatal closure in response to drought. We investigated plasticity in stomatal regulation in an isohydric (Eucalyptus camaldulensis) and an anisohydric (Acacia aptaneura) angiosperm species subject to repeated drying cycles. We also assessed foliar abscisic acid (ABA) content dynamics, aboveground/belowground biomass allocation and non-structural carbohydrates. The anisohydric species exhibited large plasticity in the turgor loss point (ΨTLP), with plants subject to repeated drying exhibiting lower ΨTLP and correspondingly larger stomatal conductance at low water potential, compared to plants not previously exposed to drought. The anisohydric species exhibited a switch from ABA to water potential-driven stomatal closure during drought, a response previously only reported for anisohydric gymnosperms. The isohydric species showed little osmotic adjustment, with no evidence of switching to water potential-driven stomatal closure, but did exhibit increased root : shoot ratios. There were no differences in carbohydrate depletion between species. We conclude that a large range in ΨTLP and biphasic ABA dynamics are indicative of anisohydric species, and these traits are associated with exposure to low minimum foliar water potential, dense sapwood and large resistance to xylem embolism.

原文链接：

http://onlinelibrary.wiley.com/doi/10.1111/pce.13077/full

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