PYR/PYL/RCAR蛋白介导植物ABA的信号转导

脱落酸(ABA)在各个植物生长发育阶段以及植物对生物与非生物胁迫的响应过程中都发挥着重要的作用。最近研究表明,在ABA信号转导途径中有3种核心组份:ABA受体PYR/PYL/RCAR蛋白、负调控因子2C类蛋白磷酸酶(PP2C)和正调控因子SNF1相关的蛋白激酶2(SnRK2),它们共同组成了一个双重负调控系统——PYR/PYL/RCAR—|PP2C—|SnRK2来调控ABA信号转导及其下游反应,且3种核心组份在植物体内的结合方式受时空和生化等因素的影响,通过特定组合形成的ABA信号转导复合体介导特定的ABA信号反应。文章就PYR/PYL/RCAR蛋白介导的植物ABA信号识别与转导途径的分子基础及其调控机制,以及PYR/PYL/RCAR—PP2C—SnRK2参与的ABA信号调控网络等研究进展做一概述,并对该领域今后的研究进行了展望。     

PYR/PYL/RCAR蛋白介导植物ABA的信号转导

脱落酸(ABA)在各个植物生长发育阶段以及植物对生物与非生物胁迫的响应过程中都发挥着重要的作用。最近研究表明, 在ABA信号转导途径中有3种核心组份：ABA受体PYR/PYL/RCAR蛋白、负调控因子2C类蛋白磷酸酶(PP2C)和正调控因子SNF1相关的蛋白激酶2(SnRK2), 它们共同组成了一个双重负调控系统-- PYR/PYL/RCAR-| PP2C-| SnRK2来调控ABA信号转导及其下游反应, 且3种核心组份在植物体内的结合方式受时空和生化等因素的影响, 通过特定组合形成的ABA信号转导复合体介导特定的ABA信号反应。文章就PYR/PYL/RCAR蛋白介导的植物ABA信号识别与转导途径的分子基础及其调控机制, 以及PYR/PYL/RCAR-PP2C-SnRK2参与的ABA信号调控网络等研究进展做一概述, 并对该领域今后的研究进行了展望。     

保卫细胞中ABA信号调控机制研究进展

脱落酸(ABA)具有调节植物快速响应逆境的重要功能。植物细胞中ABA核心信号通路由ABA受体PYR1/PYLs/ RCARs、A类碱性蛋白磷酸酶PP2Cs和Snf1相关蛋白激酶SnRK2s组成。活性氧(ROS)和Ca²⁺是保卫细胞中的重要第二信使, 调控ABA诱导的气孔关闭。该文对保卫细胞中核心ABA信号蛋白的调控以及ROS和Ca²⁺介导的ABA信号转导等最新研究成果进行综述, 旨在阐明保卫细胞中ABA信号调控机制。     

PP2C相关基因在砂梨休眠进程中的表达分析

对植物蛋白磷酸酶2C(PP2C)相关基因在砂梨Pyrus pyrifolia品系休眠进程中的表达进行分析。结果表明,砂梨PP2C相关基因与李属PP2C基因高度同源。在梨花芽休眠过程中不同PP2C基因调控的作用不同, PP2C-37-1、PP2C-37-2、PP2C-51-1、PP2C-24四个基因与内休眠调控有关,而PP2C-78对于内休眠的解除则有明显作用。PP2C蛋白磷酸酶相关基因注释到植物激素信号转导途径显示,ABA受体PYR/PYL蛋白与PP2C蛋白以及SnRK2(蛋白激酶)蛋白形成ABA信号转导的复合物可以作用于转录因子ABF从而调控梨花芽的休眠。     

植物脱落酸PYR/PYL/RCAR受体

脱落酸(abscisic acid,ABA)对植物生长发育、生物与非生物胁迫的应答具有重要作用。近年研究发现ABA在植物体中引起的信号通路源于其受体的参与,以ABA受体及ABA信号通路为基础的研究成为新的研究热点。本文简略介绍了ABA受体的研究进展概况,重点介绍细胞内ABA受体PYR/PYL/RCAR蛋白对ABA信号感知和下游转导的研究进展,最后总结了PYR/PYL/RCAR介导的ABA信号通路。     

植物ABA受体及其介导的信号转导通路

ABA是调控植物体生长发育和响应外界应激的重要植物激素之一。近年来, ABA受体的筛选和鉴定取得了突破性进展, 为植物中ABA信号转导通路的阐明奠定了重要基础。该文主要综述了ABA-binding protein/H subunit of Mgchelatase (ABAR/CHLH)、G protein-coupled receptor 2 (GCR2)、GPCR-type G protein 1/2 (GTG1/2)和pyrabactin resistant/PYR-like/regulatory component of ABA (PYR/PYL/RCAR)被报道为ABA受体的研究历程, 重点介绍了以ABAR/CHLH PYR/PYL/RCAR为受体的ABA信号转导通路模型的构建, 旨在为ABA受体及其信号转导通路的相关研究提供参考。     

低聚壳聚糖诱导的毛白杨抗病反应与ABA信号通路的关系

脱落酸(ABA)信号通路核心组分有ABA受体(PYR/PYL/RCARs)、2C型蛋白磷酸酶家族中的A亚族成员(PP2Cs)以及蔗糖非酵解型蛋白激酶2家族成员(SnRK2s)。运用BLASTP序列比对方法,在毛果杨中获得14条PtPYR、7条PtPP2C和4条PtSnRK2基因,它们分别与拟南芥AtPYR、AtPP2C和AtSnRK2基因同源。根据系统进化树分析结果,选取基因PtPYRL7、PtPYRL9、PtHAB2、PtPP2CA、PtSnRK2.3和PtSnRK2.6,设计合适的引物。以85号无性系毛白杨组培苗为材料,分别对其根部进行外源ABA和低聚壳聚糖处理,于处理3h、6h、12h和24h4个时间点取样,提取样本叶片总RNA,反转录成cDNA,进行实时荧光定量PCR分析。结果显示:ABA处理和低聚壳聚糖处理均能使PtPYRL7和PtPYRL9基因表达下调,使PtHAB2和PtPP2CA基因表达上调,使PtSnRK2.3和PtSnRK2.6基因表达先上调后下调。研究表明,ABA处理和低聚壳聚糖处理诱导毛白杨叶片中与ABA信号通路相关的基因的表达变化趋势几乎一致,说明ABA信号通路是低聚壳聚糖诱导毛白杨抗病的信号传递途径之一。     

陆地棉GhPYR1基因的克隆和功能分析

植物激素脱落酸(Abscisic acid,ABA)在植物应对干旱、盐碱等逆境胁迫以及植物种子萌发、根伸长、芽休眠等阶段发挥重要作用。PYR/PYL/RCAR蛋白家族是ABA受体,与ABA结合后能够启动ABA信号传导通路,诱导ABA应答基因的表达。利用电子克隆和RT-PCR技术从陆地棉中克隆了Gh PYR1基因,其编码的Gh PYR1蛋白与拟南芥中At PYR1蛋白相似度为73%。将Gh PYR1蛋白序列与拟南芥14个PYR/PYL/RCAR家族成员蛋白序列进行比对并构建进化树,发现它与拟南芥PYR/PYL/RCAR蛋白亚家族III亲缘关系最近。过表达Gh PYR1基因的T3代拟南芥在外源ABA处理下,其种子萌发和初期根生长均滞后于野生型,表现出对ABA更加敏感;高盐和干旱胁迫对转基因种子的萌发抑制更强烈,但苗期胁迫处理下转基因拟南芥的长势却明显优于野生型;同时在外源ABA诱导条件下ABA应答基因RD29A、RAB18的表达量较野生型有明显提高。以上结果说明Gh PYR1基因编码的蛋白是ABA的受体,过表达该基因能够提高植物对ABA的敏感性和增强应对逆境胁迫的能力。     

蛋白质翻译后修饰在ABA信号转导中的作用

脱落酸(ABA)是植物生长发育和逆境适应过程中非常关键的植物激素。植物响应ABA信号转导过程由信号识别、转导及响应级联完成, 其中心转导途径由ABA受体RCAR/PYR/PYLs、磷酸酶PP2Cs、激酶SnRK2s、转录因子和离子通道蛋白构成。蛋白磷酸化、泛素化、类泛素化和氧化还原等翻译后修饰在ABA转导途径中起重要作用。该文综述了翻译后修饰在ABA信号转导中的作用。     

蛋白质翻译后修饰在ABA信号转导中的作用

脱落酸(ABA)是植物生长发育和逆境适应过程中非常关键的植物激素。植物响应ABA信号转导过程由信号识别、转导及响应级联完成, 其中心转导途径由ABA受体RCAR/PYR/PYLs、磷酸酶PP2Cs、激酶SnRK2s、转录因子和离子通道蛋白构成。蛋白磷酸化、泛素化、类泛素化和氧化还原等翻译后修饰在ABA转导途径中起重要作用。该文综述了翻译后修饰在ABA信号转导中的作用。     

PYR/PYL/RCAR family members are major in‐vivo ABI1 protein phosphatase 2C‐interacting proteins in Arabidopsis

Abscisic acid (ABA) mediates resistance to abiotic stress and controls developmental processes in plants. The group‐A PP2Cs, of which ABI1 is the prototypical member, are protein phosphatases that play critical roles as negative regulators very early in ABA signal transduction. Because redundancy is thought to limit the genetic dissection of early ABA signalling, to identify redundant and early ABA signalling proteins, we pursued a proteomics approach. We generated YFP‐tagged ABI1 Arabidopsis expression lines and identified in vivo ABI1‐interacting proteins by mass‐spectrometric analyses of ABI1 complexes. Known ABA signalling components were isolated including SnRK2 protein kinases. We confirm previous studies in yeast and now show that ABI1 interacts with the ABA‐signalling kinases OST1, SnRK2.2 and SnRK2.3 in plants. Interestingly, the most robust in planta ABI1‐interacting proteins in all LC‐MS/MS experiments were nine of the 14 PYR/PYL/RCAR proteins, which were recently reported as ABA‐binding signal transduction proteins, providing evidence for in vivo PYR/PYL/RCAR interactions with ABI1 in Arabidopsis. ABI1–PYR1 interaction was stimulated within 5 min of ABA treatment in Arabidopsis. Interestingly, in contrast, PYR1 and SnRK2.3 co‐immunoprecipitated equally well in the presence and absence of ABA. To investigate the biological relevance of the PYR/PYLs, we analysed pyr1/pyl1/pyl2/pyl4 quadruple mutant plants and found strong insensitivities in ABA‐induced stomatal closure and ABA‐inhibition of stomatal opening. These findings demonstrate that ABI1 can interact with several PYR/PYL/RCAR family members in Arabidopsis, that PYR1–ABI1 interaction is rapidly stimulated by ABA in Arabidopsis and indicate new SnRK2 kinase‐PYR/PYL/RCAR interactions in an emerging model for PYR/PYL/RCAR‐mediated ABA signalling.     

The PP2C-SnRK2 complex: The central regulator of an abscisic acid signaling pathway

The phytohormone abscisic acid (ABA), an important bioactive compound in plants, is implicated in several essential processes such as development and the abiotic stress response. Many components have been reported to have roles in these processes. Although 2C-type protein phosphatases (PP2C) and SNF1-related protein kinases2 (SnRK2) family are known to be important signal mediators, the molecular mechanisms by which these components regulate the ABA signaling pathway have not been elucidated. Recent identification of soluble ABA receptors, PYR/PYL/RCAR, has provided a major breakthrough in understanding the signaling mechanisms of ABA and revealed the importance of PP2Cs. In addition, the physical, biochemical and physiological connections between PP2C and SnRK2 have been clearly demonstrated. Taken together, the molecular basis of the major ABA signaling pathway has been established, from perception to gene expression. In this addendum, we discuss this emerging ABA signaling pathway, which has a conventional protein phosphorylation/dephosphorylation regulatory circuit and consider its physiological and functional relevance.Key words: ABA receptor, abscisic acid, PP2C, signal transduction, SnRK2, plant hormone, phosphoarylation     

ABA signal transduction from ABA receptors to ion channels

The plant hormone abscisic acid (ABA) is involved in regulating a number of major processes such as seed dormancy, seedling development, and biotic and abiotic stress responses. The function and effect of ABA on pathogens are still unclear, but the roles of ABA in seed germination and abiotic stress responses have been well characterized. Abiotic stresses elevate ABA levels and activate ABA signaling; thus, inducing a variety of responses, including the expression of stress-related genes and stomatal closure. The past decade has witnessed many significant advances in our understanding of ABA signal transduction due to application of a combination of approaches including genetics, biochemistry, electrophysiology, and chemical genetics. A number of proteins associated with the ABA signal transduction pathway such as PYR/PYL/RCAR family of START proteins, have been identified. These ABA receptors bind to ABA and positively regulate ABA signaling via inactivation of PP2C phosphatase activity, which inhibits SnRK2-type kinases by direct interaction and dephosphorylation. Additionally, SnRK2-type kinases and PP2Cs interact with one another and with other components of ABA signaling and function as positive and negative ABA regulators, respectively. In this review, we focus on ABA function to abiotic stresses and highlight each component in relation to ABA and its interactions.     

The ABA signal transduction mechanism in commercial crops: learning from Arabidopsis

The phytohormone abscisic acid (ABA) affects a wide range of stages of plant development as well as the plant's response to biotic and abiotic stresses. Manipulation of ABA signaling in commercial crops holds promising potential for improving crop yields. Several decades of research have been invested in attempts to identify the first components of the ABA signaling cascade. It was only in 2009, that two independent groups identified the PYR/PYL/RCAR protein family as the plant ABA receptor. This finding was followed by a surge of studies on ABA signal transduction, many of them using Arabidopsis as their model. The ABA signaling cascade was found to consist of a double-negative regulatory mechanism assembled from three protein families. These include the ABA receptors, the PP2C family of inhibitors, and the kinase family, SnRK2. It was found that ABA-bound PYR/RCARs inhibit PP2C activity, and that PP2Cs inactivate SnRK2s. Researchers today are examining how the elucidation of the ABA signaling cascade in Arabidopsis can be applied to improvements in commercial agriculture. In this article, we have attempted to review recent studies which address this issue. In it, we discuss various approaches useful in identifying the genetic and protein components involved. Finally, we suggest possible commercial applications of genetic manipulation of ABA signaling to improve crop yields.