生长素通过MAPK介导的超长链脂肪酸合成调控侧根发育

促分裂原活化蛋白激酶(MAPK)信号级联通路是真核生物中高度保守的重要信号系统, 通过激酶逐级磷酸化传递并放大上游信号, 进而调控细胞反应。MAPK信号通路不仅介导植物响应环境变化, 而且在调节植物生长发育过程中发挥重要作用。近期, 山东大学丁兆军课题组研究发现, 植物重要激素生长素能够通过激活MPK14调控下游ERF13的磷酸化, 进而影响超长链脂肪酸的合成并调控侧根发育。该研究从全新的角度解析了侧根起始的新机制, 并进一步证实生长素和古老的信号转导模块MAPKs相偶联的分子机制。侧根作为植物响应环境最重要的器官之一, MAPK信号通路在侧根发育过程中的功能解析可为阐明植物如何整合发育和环境信号提供新思路。     

植物富含亮氨酸重复序列型类受体蛋白激酶的生物学功能

介绍了植物富含亮氨酸重复序列(leucine-rich repeat,LRR)型类受体蛋白激酶概念、最近发现的这类蛋白激酶的亚结构域特征;总结了目前已确定其功能的LRR型类受体蛋白激酶,并分别阐述了它们在参与植物抗逆性反应、发育调控及激素的信号转导等过程中的生物学功能;着重介绍和讨论了LRR型类受体蛋白激酶复合物之间及其与下游成分KAPP之间互作而产生信号传递的分子机理.最后展望了LRR型类受体蛋白激酶生物学功能、信号转导机制、以及应用于生产实践的研究前景.     

植物非经典生长素信号转导通路解析

植物激素生长素参与调控植物生长发育的各个过程,包括胚胎发育、器官发生和向性运动等。植物通过协调生长素的合成代谢、极性运输以及信号转导来实现对不同生长发育过程的精准调控。生长素的功能依赖于其信号被感知后经由信号转导通路转换为下游复杂多样的反应。经典的生长素信号转导通路阐明了细胞核内从SCF~(TIR1/AFB)受体到Aux/IAA蛋白的泛素化降解最终通过ARF转录因子调控基因转录的完整生长素响应过程。该核内信号通路揭示了生长素转录调控生长发育的诸多分子机制,但植物生长发育调控过程中仍有许多生长素响应过程无法通过该经典信号通路解析。重点阐述生长素非经典信号通路的调控机制及其对植物生长发育的重要作用,并讨论和展望生长素非经典信号通路研究目前所面临的挑战以及研究前景。     

非TIR1受体依赖型激活生长素信号的新机制

依赖于受体TIR1以及下游Aux/IAAs-ARFs介导的信号通路是目前研究最为深入的生长素信号转导途径。徐通达课题组最新研究发现, 高浓度生长素能够诱导质膜定位的TMK1激酶发生剪切, 导致其羧基(C-)端部分转入细胞核并磷酸化修饰细胞核内的非经典IAA32/34, 后者通过与生长素响应转录因子ARFs互作, 调控下游基因表达, 从而解析了生长素通过TMK1-IAA32/34-ARFs通路调控植物顶端弯钩内外侧差异性生长的分子机制。该研究发现了一条新的生长素TMK1- IAA32/34-ARFs信号途径, 此信号通路独立于经典生长素受体TIR1介导的生长素信号转导通路。     

非TIR1受体依赖型激活生长素信号的新机制

依赖于受体TIR1以及下游Aux/IAAs-ARFs介导的信号通路是目前研究最为深入的生长素信号转导途径。徐通达课题组最新研究发现, 高浓度生长素能够诱导质膜定位的TMK1激酶发生剪切, 导致其羧基(C-)端部分转入细胞核并磷酸化修饰细胞核内的非经典IAA32/34, 后者通过与生长素响应转录因子ARFs互作, 调控下游基因表达, 从而解析了生长素通过TMK1-IAA32/34-ARFs通路调控植物顶端弯钩内外侧差异性生长的分子机制。该研究发现了一条新的生长素TMK1- IAA32/34-ARFs信号途径, 此信号通路独立于经典生长素受体TIR1介导的生长素信号转导通路。     

类受体激酶调控根生长发育的研究进展

类受体激酶是一类具有激酶活性的单次跨膜受体,通过接收和传递胞外信号调控细胞的生理反应,参与植物生长发育过程。植物根在生长发育过程中受到大量的外部刺激和内源性发育信号的影响,植物必须通过整合这些信号并转化为细胞反应,才能适应不断变化的环境条件;植物类受体激酶作为细胞膜上的信息监测者,通过与外源和内源信号的通讯调控根的生长发育。该文对近年来国内外有关类受体激酶的结构、分类及其作用机制,特别是植物类受体激酶在根发育信号转导途径中的功能和作用等方面的研究进展进行综述,为进一步揭示植物类受体激酶在根生长发育中的功能及其作用机制提供参考。     

植物凝集素类受体蛋白激酶研究进展

自然界中植物的生长发育受到各种环境变化的影响。为了响应外界各种环境条件,植物演化出一系列识别和传递环境信号的蛋白分子,其中比较典型的是植物细胞质膜上的类受体蛋白激酶(RLKs)。凝集素类受体蛋白激酶(LecRLKs)是类受体蛋白激酶家族中的一个亚族,它主要包含3个结构域:细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域。根据细胞外凝集素结构域的不同,LecRLKs可分为3种不同类型:L、G和C型。近年来,研究表明LecRLKs在植物生物/非生物胁迫和发育调控中发挥非常重要的作用。该文综述了植物凝集素类受体蛋白激酶的研究历史、结构特点、分类以及生物学功能,并重点阐述凝集素类受体蛋白激酶在植物生物/非生物胁迫响应和调控发育方面的功能。对不同类型和不同功能的植物凝集素类受体蛋白激酶进行阐述将有利于对该类蛋白开展功能研究,并为作物改良提供有益借鉴。     

植物凝集素类受体蛋白激酶研究进展

自然界中植物的生长发育受到各种环境变化的影响。为了响应外界各种环境条件,植物演化出一系列识别和传递环境信号的蛋白分子,其中比较典型的是植物细胞质膜上的类受体蛋白激酶(RLKs)。凝集素类受体蛋白激酶(LecRLKs)是类受体蛋白激酶家族中的一个亚族,它主要包含3个结构域:细胞外凝集素结构域、跨膜结构域和细胞内激酶结构域。根据细胞外凝集素结构域的不同, LecRLKs可分为3种不同类型:L、G和C型。近年来,研究表明LecRLKs在植物生物/非生物胁迫和发育调控中发挥非常重要的作用。该文综述了植物凝集素类受体蛋白激酶的研究历史、结构特点、分类以及生物学功能,并重点阐述凝集素类受体蛋白激酶在植物生物/非生物胁迫响应和调控发育方面的功能。对不同类型和不同功能的植物凝集素类受体蛋白激酶进行阐述将有利于对该类蛋白开展功能研究,并为作物改良提供有益借鉴。     

生长素信号转导研究进展

植物激素生长素影响植物生长中几乎所有的方面,包括植物细胞的生长、分裂和分化,以及植物从胚胎发育到生殖发育的各个过程中。生长素的研究主要围绕合成与代谢、运输和信号转导而展开。植物细胞对生长素的响应和信号转导主要通过细胞核内的TIR1/AFB-Aux/IAA-ARF信号通路来完成。另外,细胞表面起始的信号通路主要调控生长素的快速响应,而SKP2A通路介导了生长素对细胞周期的调控。概述了三条生长素信号转导通路目前的研究进展,并介绍了生长素信号转导中具体的研究工具。基于该领域的研究现状,提出了生长素信号转导方面有待进一步研究的方向,包括TIR1/AFB-Aux/IAA-ARF复合体的调控机制研究、生长素调控冠部和根部生长的差异性研究、以及对细胞表面起始信号途径的进一步探索。     

生长素在微生物调控根发育过程中的作用

很多微生物通过分泌生长素和生长素前体与植物建立了有益的关系并改变植物根系的形态结构,此外,微生物分泌的其他代谢产物也能改变植物生长素信号通路。因此,生长素和生长素信号通路在微生物调控植物根系发育的过程中起着至关重要的作用。该文从生长素合成、生长素信号和生长素极性运输3个方面总结了生长素在微生物调控植物根系发育过程中的作用,主要包括微生物增加了植物内源生长素的含量、增强了生长素的信号和调控PIN蛋白的表达水平,进而如何调控植物生理和分子水平来适应微生物对其根系的改变,为进一步开展该方面的研究奠定了基础。     

Cryptochromes,Phytochromes, and COP1 Regulate Light-Controlled Stomatal Development in Arabidopsis

In Arabidopsis thaliana, the cryptochrome (CRY) blue light photoreceptors and the phytochrome (phy) red/far-red light photoreceptors mediate a variety of light responses. COP1, a RING motif–containing E3 ubiquitin ligase, acts as a key repressor of photomorphogenesis. Production of stomata, which mediate gas and water vapor exchange between plants and their environment, is regulated by light and involves phyB and COP1. Here, we show that, in the loss-of-function mutants of CRY and phyB, stomatal development is inhibited under blue and red light, respectively. In the loss-of-function mutant of phyA, stomata are barely developed under far-red light. Strikingly, in the loss-of-function mutant of either COP1 or YDA, a mitogen-activated protein kinase kinase kinase, mature stomata are developed constitutively and produced in clusters in both light and darkness. CRY, phyA, and phyB act additively to promote stomatal development. COP1 acts genetically downstream of CRY, phyA, and phyB and in parallel with the leucine-rich repeat receptor-like protein TOO MANY MOUTHS but upstream of YDA and the three basic helix-loop-helix proteins SPEECHLESS, MUTE, and FAMA, respectively. These findings suggest that light-controlled stomatal development is likely mediated through a crosstalk between the cryptochrome-phytochrome-COP1 signaling system and the mitogen-activated protein kinase signaling pathway.     

Molecular characterization of the cytoplasmic interacting protein of the receptor kinase IRK expressed in the inflorescence and root apices of Arabidopsis

Meristem maintenance and differentiation is regulated by intercellular communication through receptor-like kinases (RLKs) in plants, but the underlying molecular mechanisms of RLK signaling remain largely unknown. A cytoplasmic interactor for inflorescence and root apices receptor-like kinase (IRK), which is a typical meristematic RLK with leucine-rich repeats in Arabidopsis, was identified using a yeast two-hybrid assay and named IRK-interacting protein (IRKI). IRKI is a novel but highly conserved protein found in higher plants. The interaction between IRK and IRKI was confirmed by an in vitro pull-down assay and supported by their simultaneous expression in actively dividing cells in meristems. In the root tip, IRKI expression and localization visualized by green fluorescence protein (GFP) were observed in the quiescent center, initial cells, and immature stele cells. IRKI expression was expanded by exogenous auxin treatment and repressed by inhibitor treatment of polar auxin transport.     

Auxin induces mitogenic activated protein kinase (MAPK) activation in roots of Arabidopsis seedlings

Genome analyses have shown that plants contain gene families encoding various components of mitogen-activated protein kinase (MAPK) signaling pathways. Previous reports have described the involvement of MAPK pathways in stress and pathogen responses of leaves and suspension-cultured cells. Here we show that auxin treatment of Arabidopsis roots transiently induced increases in protein kinase activity with characteristics of mammalian ERK-like MAPKs. The MAPK response we monitored was the result of hormonal action of biologically active auxin, rather than a stress response provoked by auxin-like compounds. Auxin-induced MAPK pathway signaling was distinguished genetically in the Arabidopsis auxin response mutant axr4, in which MAPK activation by auxin, but not by salt stress, was significantly impaired. Perturbation of MAPK signaling in roots using inhibitors of a mammalian MAPKK blocked auxin-activated transgene expression in BA3-GUS seedlings, while potentiating higher than normal levels of MAPK activation in response to auxin. Data presented here indicate that MAPK pathway signaling is positively involved in auxin response, and further suggest that interactions among MAPK signaling pathways in plants influence plant responses to auxin.     

Reinforcing the idea of signalling in the stomatal pathway

Stomata are plant epidermal structures that regulate gas exchange with the atmosphere. In Arabidopsis, mutations in TOO MANY MOUTHS (TMM) disrupt a range of processes related to stomatal development and patterning. Recently, the sequence and the expression pattern of TMM were reported. TMM encodes a leucine-rich-repeat-containing, receptor-like protein that lacks a cytoplasmic kinase domain and that is expressed in postprotodermal cells. Several lines of evidence suggest that TMM and STOMATAL DENSITY AND DISTRIBUTION1, a putative subtilisin-like serine protease, might act in the same signalling pathway.     

OsRPK1, a novel leucine-rich repeat receptor-like kinase,negatively regulates polar auxin transport and root development in rice

Background

Leucine-rich-repeat receptor-like kinases (LRR-RLKs) represent the largest subfamily of putative RLKs in plants. Although several members in this subfamily have been identified, the studies about the relationships between LRR-RLKs and root development are still few. We previously identified a novel LRR-RLK in rice roots, and named it OsRPK1.

Methods

In this study, we first detected OsRPK1 kinase activity in vitro, and assessed its expression profile. We then investigated its biological function using transgenic rice plants over- and under-expressing OsRPK1.

Results

The OsRPK1 gene, which encodes a Ca^2 +-independent Ser/Thr kinase, was predominantly expressed in root tips, leaf blades, and undifferentiated suspension cells, and was markedly induced by treatment with auxin or ABA. Knockdown of OsRPK1 promoted the growth of transgenic rice plants, and increased plant height and tiller numbers. In contrast, over-expressing plants showed undeveloped adventitious roots, lateral roots, and a reduced root apical meristem. OsRPK1 over-expression also inhibited the expression of most auxin efflux carrier OsPIN genes, which was accompanied by changes in PAT and endogenous free IAA distribution in the leaves and roots.

Conclusions

The data indicated that OsRPK1, a novel leucine-rich-repeat receptor-like kinase, affects the root system architecture by negatively regulating polar auxin transport in rice.

General significance

This study demonstrated a common regulatory pathway of root system development in higher plants, which might be initiated by external stimuli via upstream receptor-like kinases and downstream carriers for polar auxin transport.     

Diverse roles of SERK family genes in plant growth,development and defense response

Plant receptor-like protein kinases (RLKs) are transmembrane proteins with an extracellular domain and an intracellular kinase domain, which enable plant perceiving diverse extracellular stimuli to trigger the intracellular signal transduction. The somatic embryogenesis receptor kinases (SERKs) code the leucine-rich-repeat receptor-like kinase (LRR-RLK), and have been demonstrated to associate with multiple ligand-binding receptors to regulate plant growth, root development, male fertility, stomatal development and movement, and immune responses. Here, we focus on the progress made in recent years in understanding the versatile functions of Arabidopsis SERK proteins, and review SERK proteins as co-receptor to perceive different endogenous and environmental cues in different signaling pathway, and discuss how the kinase activity of SERKs is regulated by various modification.     

MAPK级联途径参与ABA信号转导调节的植物生长发育过程

植物激素ABA参与调控植物生长发育和生理代谢以及多种胁迫应答过程,促分裂原活化蛋白激酶（MAPK）级联途径应答于多种生物和非生物胁迫,广泛参与调控植物的生长发育。MAPK级联途径与ABA信号转导协同作用参与调控植物种子萌发、气孔运动和生长发育,本文主要归纳了植物中受ABA调控激活的MAPK级联途径成员,阐述了它们参与ABA信号转导调控植物生理反应和生长发育的过程,并对MAPK级联途径与ABA信号转导的研究方向作出了展望,指出对MAPK下游底物的筛选是完善MAPK级联途径的重要组成部分。     

生长素信号转导研究进展

长素的信号转导是一个复杂的网络系统,在信号的感知上,除了存在ABPI介导的膜上感知途径外,还有其他的感知途径。G蛋白参与诱导生长素信号的胞内传递,生长素信号转导的第二信使包括离子型第二信使、磷酯酶A2、脂活化蛋白激酶、MAPK和PINOIND等。AUX／IAA蛋白的泛素化降解在生长素反应中发挥关键性作用,ARF和AUX／IAA蛋白相互作用调节生长素响应基因的转录。