ABA signal transduction at the crossroad of biotic and abiotic stress responses

Abscisic acid (ABA) regulates key processes relevant to seed germination, plant development, and biotic and abiotic stress responses. Abiotic stress conditions such as drought induce ABA biosynthesis initiating the signalling pathways that lead to a number of molecular and cellular responses, among which the best known are the expression of stress-related genes and stomatal closure. Stomatal closure also serves as a mechanism for pathogen defence, thereby acting as a platform for crosstalk between biotic and abiotic stress responses involving ABA action. Significant advances in our understanding of ABA signal transduction have been made with combination of approaches including genetics, biochemistry, electrophysiology and chemical genetics. Molecular components associated with the ABA signalling have been identified, and their relationship in the complex network of interactions is being dissected. We focused on the recent progress in ABA signal transduction, especially those studies related to identification of ABA receptors and downstream components that lead ABA signal to cellular response. In particular, we will describe a pathway model that starts with ABA binding to the PYR/PYL/RCAR family of receptors, followed by inactivation of 2C-type protein phosphatases and activation of SnRK2-type kinases, and eventually lead to activation of ion channels in guard cells and stomatal closure.     

Global gene expression responses to waterlogging in roots of sesame (Sesamum indicum L.)

Waterlogging stress lowers yields in sesame (Sesamum indicum L.). A major component of waterlogging stress is the lack of oxygen available to submerged tissues. Although the morphology and physiology of plants grown under anaerobic conditions have been studied in detail, limited work has been done to elucidate adaptations at the molecular level. To gain comprehensive insight into how sesame responds to hypoxia at the genome level, we performed gene expression profiling at two time points during a 36-h period following hypoxic treatment using a whole-genome RNA-Seq analysis. We identified sets of significantly positively and negatively expressed genes (induced and repressed, respectively) in response to hypoxia with distinct temporal profiles. The genes that were affected were associated with glycolysis, nitrogen metabolism, starch and sucrose metabolism and plant hormone signal transduction and indicated the upregulation of particular pathways (glycolysis/glycogenesis) in the Kyoto Encyclopedia of Genes and Genomes. Moreover, significant changes in the expression of genes were found for pathways, including flavone and flavonol biosynthesis, steroid biosynthesis, photosynthesis, cysteine and methionine metabolism, glutathione metabolism, as well as phenylpropanoid biosynthesis, spliceosome, circadian rhythm. This study helps in elucidating the molecular mechanisms of waterlogging tolerance and provides a basis for the genetic engineering of sesame.     

水稻穗发育功能基因对穗期氮肥的响应

为探讨氮肥对水稻(Oryza sativa)穗发育的调控作用, 使用高通量测序技术检测氮肥处理前后水稻叶片和幼穗组织中转录组的变化, 并从中筛选到大量差异表达基因。这些基因的功能涉及转录调控、激素代谢和信号转导、物质代谢和转运、胁迫响应、信号转导(受体)和蛋白质降解等。同时对目前克隆得到的穗发育相关基因进行分析, 发现在氮素穗肥的作用下, 部分重要功能基因的表达量发生了明显变化, 其中一些基因还参与调控水稻株高、抽穗期、分蘖和结实率等性状。对这些差异表达基因的功能研究有助于揭示氮素穗肥调控水稻每穗颖花数的分子机制。     

油菜素内酯调控作物农艺性状和非生物胁迫响应的研究进展

植物对不利环境的适应依赖于将外部胁迫信号传递到内部信号通路中,在进化过程中形成一系列的胁迫响应机制。其中,油菜素内酯(brassinosteroids, BRs)是一种类固醇激素,广泛参与植物生长发育和逆境响应过程。BRs被包括受体BRI1和共受体BAK1在内的细胞表面受体感知,继而触发信号级联,导致蛋白激酶BIN2的抑制和转录因子BES1/BZR1的激活,BES1/BZR1可直接调控数千个下游响应基因的表达。在模式植物拟南芥中的研究表明,BR的生物合成和信号转导通路成员,特别是BIN2和其下游的转录因子BES1/BZR1,可以被各种环境因子广泛地调节。本文系统总结了BR相关的最新研究进展,对BR的生物合成和信号转导是如何被复杂的环境因子所调节,以及BR与环境因子如何协同调控作物重要农艺性状、冷胁迫和盐胁迫的响应进行了综述。     

干旱胁迫下茶树基因表达的AFLP分析

利用cDNA-AFLP技术分析了茶树在干旱胁迫诱导下的基因表达差异,通过256对引物组合共获得27个差异表达片段（TDF）,通过BLAST比对分析,按其功能分为转录因子、基础代谢相关蛋白、抗逆蛋白、信号转导蛋白,此外还有一些假设蛋白、未知蛋白和没有比对的基因片段。同时利用RT-PCR对片段GH2和GH15进行验证,表明GH2和GH15片段均受到干旱胁迫诱导表达。这些研究结果显示茶树在干旱胁迫下的逆境反应非常复杂,涉及多种代谢过程中的众多基因。