植物小G蛋白研究进展

小G蛋白是和异三聚体G蛋白α亚基偶联的单体鸟苷酸结合蛋白,所有的小G蛋白从属于Ras超家族．植物小G蛋白超家族尤其是ROP家族在信号转导及生长发育中起了重要的“分子开关”作用,它们参与调控花粉管的伸长、根毛的发育及激素信号转导等过程．主要介绍了小G蛋白的种类、调节机制、ROP家族的功能及靶物,旨在揭示植物小G蛋白功能的多样性．     

G蛋白与细胞信号转导

该文主要阐述了G蛋白结构、偶联受体、下游效应器以及蛋白信号转导的有效途径,并且说明了在进行植物细胞信号转导的过程中,植物细胞G蛋白具有非常重要的作用。     

百日咳毒素与霍乱毒素对乙酰酰胆碱诱导气孔运动的影响

在动物细胞中神经递质乙酰胆碱与其受体结合后，通过G蛋白的偶联传递信号。在植物中，乙酰胆碱也普遍存在并参与调节许多生理过程。乙酰胆碱及其受体参与了气孔运动的调节，G蛋白的激活剂霍乱毒素与抑制剂百日咳毒素影响乙酰胆碱诱导的气孔开放，而且仅在含Ca^2 的介质中才能起作用；同时用Ca^2 荧光探针Fluo-3检测保卫细胞胞质Ca^2 动态变化，表明乙酰胆碱的胞内信号转导中有Ca^2 的参与。由此推测在毒蕈碱型乙酰胆碱受体介导乙酰胆碱诱导的气孔运动中，可能存在与G蛋白偶联的信号转导。     

G蛋白信号转导调节因子的研究

G蛋白信号转导调节因子（Regulator of Gprotein signaling,RGS）是G蛋白的信号转导系统的负性调节因子,大部分RGS蛋白通过GTP酶激活蛋白方式发挥作用．本文概述了G蛋白信号转导调节因子的结构、功能、意义及国际最新的研究趋势．对RGS的深入研究有利于对信号转导调节的了解．     

镁素营养研究进展

概述了近年来在原核生物、酵母及高等植物中有关镁素转运蛋白家族及其基因如CorA、Alrp、AtMGT等的研究进展，并对目前研究较少的逆境胁迫下与镁离子有关信号转导的内容也做了简述，且对今后有关的研究趋势作了进一步展望．     

拟南芥信号传递途径

探讨拟南芥发育过程中一些调控基因表达的信号是如何传递的。广泛查阅近期有关发育生物学方面的文章,综述了拟南介信号传递的过程。发现植物体有许多与动物相同的信号传递途径,如磷酸化级联途径。在拟南芥中Raf1激酶,蛋白激酶（MEK）、蛋白激酶激酶（MAPK）都与信号转导直接有关。另外发现磷酸化过程在一定程度上依赖于卷须蛋白（CLV1）的自动磷酸化。植物信号转导途径类似于动物,通过磷酸化作用传递各种信号,来保持细胞增殖和分化的平衡。     

支架蛋白对丝裂原活化蛋白激酶信号途径中震荡的抑制

通过一种两体支架蛋白参与的丝裂原活化蛋白激酶(mitogen-activated protein kinase,MAPK)信号转导模型,研究了支架蛋白参与的存在负反馈的MAPK信号转导途径.支架蛋白(scaffold protein)既可以促进信号过程,也可以抑制信号的转导.由系统中支架蛋白的浓度以及支架与信号分子的相互作用共同决定了增加支架浓度造成的不同结果.不仅如此,系统中支架蛋白浓度的增加,还会抑制负反馈系统中出现的持续震荡.     

LysM蛋白在植物免疫中的作用

溶解素基序（LysM）是在多种蛋白质中普遍存在的结构域.植物LysM蛋白能够感知几丁质及其寡糖等分子配体，从而启动植物对病原菌的免疫反应.在水稻、拟南芥等植物免疫应答过程中，LysM蛋白作为一种重要的模式识别受体，通过不同形式的寡聚化，激活多种类受体胞质激酶及其下游的MAPK（mitogen activated protein kinase）级联反应传递信号.同时，蛋白质可逆磷酸化和蛋白质降解途径可以负调节LysM蛋白介导的防御信号转导.文章综述了植物免疫过程中LysM蛋白介导的信号转导分子机制.     

拟南芥gpa1-1/Athos1双重突变体的筛选鉴定

异三聚体G蛋白和NO都是植物体内作用广泛的细胞信号物质，将gpa1-1和Amos1进行杂交，筛选鉴定拟南芥G蛋白仪亚基与NO合酶基因双重缺失突变纯合体，可为研究相应基因及其功能提供直接模式材料，也为在分子水平上探索异三聚体G蛋白和NO的各种生理作用及其在信号转导中的相互关系提供模式材料．     

植物脱落酸信号转导研究进展

本文从脱落酸(ABA)结合位点与受体、Ca~(2 )信号系统、蛋白质的可逆磷酸化、磷酸肌醇系统及 G 蛋白等几个方面介绍了脱落酸信号转导的研究进展。     

Primary structure and functional expression of a cyclic nucleotide-activated channel from olfactory neurons.

Odorant signal transduction occurs in the specialized cilia of the olfactory sensory neurons. Considerable biochemical evidence now indicates that this process could be mediated by a G protein-coupled cascade using cyclic AMP as an intracellular second messenger. A stimulatory G protein alpha subunit is expressed at high levels in olfactory neurons and is specifically enriched in the cilia, as is a novel form of adenylyl cyclase. This implies that the olfactory transduction cascade might involve unique molecular components. Electrophysiological studies have identified a cyclic nucleotide-activated ion channel in olfactory cilia. These observations provide evidence for a model in which odorants increase intracellular cAMP concentration, which in turn activates this channel and depolarizes the sensory neuron. An analogous cascade regulating a cGMP-gated channel mediates visual transduction in photoreceptor cells. The formal similarities between olfactory and visual transduction suggest that the two systems might use homologous channels. Here we report the molecular cloning, functional expression and characterization of a channel that is likely to mediate olfactory transduction.     

Gustducin is a taste-cell-specific G protein closely related to the transducins.

A novel G protein alpha-subunit (alpha-gustducin) has been identified and cloned from taste tissue. alpha-Gustducin messenger RNA is expressed in taste buds of all taste papillae (circumvallate, foliate and fungiform); it is not expressed in non-sensory portions of the tongue, nor is it expressed in the other tissues examined. alpha-Gustducin most closely resembles the transducins (the rod and cone photoreceptor G proteins), suggesting that gustducin's role in taste transduction is analogous to that of transducin in light transduction.     

禾谷炭疽菌中候选G蛋白偶联受体蛋白理化性质及遗传关系分析

GPCR是G蛋白偶联受体的简称,作为一类具有七跨膜螺旋结构的重要细胞表面受体,对生物中细胞信号转导过程发挥着重要作用。然而,对于禾谷炭疽菌候选GPCR蛋白的理化性质及遗传关系尚不清楚,制约着对该菌致病机制的研究。本研究基于对禾谷炭疽菌中220个候选GPCR蛋白序列,利用SignalP 5.1、ProtParam和ProtScal等在线预测程序对上述蛋白中的信号肽、理化性质、疏水性进行明确,结果表明,禾谷炭疽菌中仅有7个含有信号肽的候选GPCR蛋白,理论等电点主要集中在大于6.01,多属于中性或碱性蛋白,均为疏水性蛋白,同时利用MEGA软件对上述蛋白的遗传关系进行解析,明确候选GPCR蛋白主要分为A、B、C三类,上述类别与其保守结构域有着密切关系。该研究为进一步开展禾谷炭疽菌GPCR蛋白功能解析提供了重要的理论支撑,也为其他炭疽菌中GPCR蛋白功能研究提供了重要的理论基础。     

皮肤特异表达钙调素类蛋白研究进展

钙调素是广泛存在于各种动植物细胞的信号转导分子,近年在皮肤中发现了一些钙调素类蛋白,其分布、特征、功能都与钙调素不同,在表皮的分化发育中发挥重要作用。本文就此作一简单介绍。     

禾谷炭疽菌中候选G蛋白偶联受体蛋白的找寻

G蛋白偶联受体(G protein-coupled receptor, GPCR)是生物中一类具有典型七跨膜结构域的重要细胞表面受体,对细胞信号转导过程具有重要作用。禾谷炭疽菌严重危害着玉米、高粱等禾本科植物的产业发展,然而,对于该菌中GPCR蛋白数量及功能尚未有系统性报道。基于典型GPCR蛋白序列所具有的七跨膜保守结构域特征,通过TMHMM、Philius和TOPCONS 3种常用软件进行在线分析,明确全部蛋白的预测功能与蛋白数量、跨膜结构域数量与蛋白数量、氨基酸序列长度与蛋白数量之间的关系。结果表明,禾谷炭疽菌中含有243个具有七跨膜结构域蛋白(涉及含有7个跨膜结构域但不含有信号肽序列蛋白或者含有信号肽序列的具有8个跨膜结构域的蛋白),进一步通过SMART保守结构域分析,可知该菌中存在220个候选GPCR蛋白。该研究为进一步开展禾谷炭疽菌候选GPCR蛋白的理化性质解析提供了重要的数据支撑,也为进一步明确GPCR蛋白及其功能的研究奠定重要的理论基础。     

Involvement of heterotrimeric G protein in signal transduction of extracellular calmodulin in regulatingrbcS expression

The role of heterotrimeric G protein in signal transduction pathway of extracellular calmodulin in regulating rbcS expression was examined in suspension-cultured cells of transgenic tobacco. Pharmalogical experiments indicated that G protein agonist cholera toxin enhanced rbcS expression and heterotrimeric G protein antagonist pertussis toxin inhibited rbcS expression in transgenic tobacco cells. Pertussis toxin also inhibited the enhancement effect caused by exogenous purified calmodulin on rbcS expression, whereas cholera toxin completely reversed the inhibitory effects caused by anti-calmodulin serum on rbcS expression. The right side-out vesicles from tobacco cell membrane were purified, which contained all of substrates for fluometric assay of GTPase activity. Exogenous purified calmodulin, when adding directly to the medium of plasma membrane vesicles, significantly activated GTPase activity in the right side-out plasma membrane vesicles, and this increase in GTPase activity was completely inhibited both by heterotrimeric G proteins antagonist pertussis toxin and nonhy-drolyzable GTP analogs GMP-PCP. These results provided the evidence that heterotrimeric G proteins may be involved in signal transduction pathways of extracellular calmodulin to regulate rbcS gene expression.     

Stimulation of specific GTP binding and hydrolysis activities in lymphocyte membrane by interleukin-2

Interleukin-2 (IL-2) is a polypeptide growth factor which stimulates the proliferation and differentiation of T lymphocytes. The receptor for IL-2 is expressed on activated T lymphocytes, cloned IL-2 dependent cells and several other cell types. Analysis of the primary structure and of immune-precipitated receptor suggests that this molecule has no intrinsic signal transduction function, unlike other growth factors. IL-2 interaction with a high affinity receptor has been shown, however, to activate the calcium/phospholipid-dependent protein kinase C (PK-C) presumably via phosphoinositide hydrolysis. Members of a family of closely related guanine nucleotide binding proteins (G proteins) regulate a diverse group of metabolic events. Two of them, Gs and Gi, stimulate and inhibit adenylate cyclase activity respectively, and other G proteins are involved in diverse signal transduction system. Another member, Go, has no known function and activation of phospholipase C has been attributed to the action of an unidentified G protein, Gp. Since it has been observed that IL-2 inhibits the catalytic activity of adenylate cyclase and that agents such as PGE2 which stimulate adenylate cyclase activity inhibit the lymphoproliferative response to IL-2, association of GTP binding proteins with IL-2 signal transduction was investigated. In this report we describe for the first time the participation of a GTP binding protein in the action of a polypeptide growth factor, interleukin-2.     

Heterotrimeric G protein participated in modulation of cytoplasmic calcium concentration in pollen cells

Cytoplasmic free calcium concentration([Ca2+]c) in pollen cells of Lilium daviddi is measured with confocal laser scanning microscopy to investigate the effect of heterotrimeric G protein (G protein) on [Ca2+]c and the possible signal transduction pathway of G protein triggering cellular calcium signal. After application, cholera toxin (CTX), an agonist of G protein, triggers a transient increase of [Ca2+]c in pollen cells, and evokes a spatial-temporal characteristic calcium dynamics; while pertussis toxin (PTX), a G protein antagonist, leads to the decrease of [Ca2+]c. Both L-type Ca2+ channel blocker verapamil and inhibitor of IP3 receptor heparin inhibit CTX-induced [Ca2+]c increase. The results show that G protein may play a role in the modulation of [Ca2+]c through enhancing the extracellular Ca2+ influx and releasing of Ca2+ from intracellular stores.     

胶孢炭疽菌RGS蛋白生物信息学分析

胶孢炭疽菌侵染众多植物引起的炭疽病,给各国农林业生产造成了巨大经济损失.RGS作为植物病原菌G蛋白信号转导过程中的重要调节因子,在众多生理生化过程中发挥着重要作用.本研究基于前期研究所获得的胶孢炭疽菌中所含有的12个RGS,通过保守结构域、理化性质、疏水性、细胞信号肽、跨膜区结构、亚细胞定位以及二级结构等生物信息学分析,明确上述RGS在保守结构域、理化性质、疏水性、信号肽、跨膜区域、二级结构等方面均具有较大的一致性特点;此外,通过对上述RGS进行遗传关系比较分析,发现不同菌株中的RGS彼此之间具有较近的亲缘关系.该研究为深入开展胶孢炭疽菌RGS功能研究打下坚实的理论基础.