谷氨酸受体基因参与拟南芥根系生长响应外源氨基酸的分子功能研究

Ionotropic glutamate receptors (iGLuRs) are amino acids-gated cation channels in animals, and possess molecular functions in the regulation of excitatory neurotransmission. In Arabidopsis, although a gene family termed AtGLR containing 20 members and homologous to iGLuR has been identified for many years, little is known about molecular biological roles of most members of this gene family. Because of the occurrence of a large spectrum of amino acids in soils and a long-term biological evolution, plants have developed abilities to take up and respond or sense soil amino acids, however, molecular identities underlying plant (root) growth in response to different amino acids have so far not been established. Based on our preliminary achievements gained from the investigation of AtGLR functions and mechanisms of plant root development, in this proposal we are first going to perform phenotype screening of root growth of 20 AtGLR mutant lines sensitive to amino acids applied externally, thus identifying target AtGLR genes involved in root amino acid-response. Subsequently, molecular biological functions of our interested AtGLRs will have been characterized in details by using combined approaches including e.g. gene cloning and expression, electrophysiological study, monitoring of Ca2+ flux into the cytoplasm, histochemical and anatomical analysis, etc. Our results or achievements from this project are expected not only to fundamentally elucidate molecular functions of certain AtGLRs (e.g. as ion channels) and their roles in participating some critical biological events like root growth in relation to sensing of soil amino acids, but also to provide valuable molecular and genetic bases for controlling or manipulating root development and architecture as well as improving plant ability to grow adaptively in soil environments.

离子型谷氨酸受体(iGLuR)是动物中一类由氨基酸为配体门控的阳离子通道，具有调节兴奋性神经传递等分子功能。拟南芥中存在与iGLuR同源的含20个成员的基因家族即AtGLR，但其大部分成员基因的生物学功能尚未知。土壤中各种氨基酸的存在以及长期的生物进化，使植物具备了吸收和响应氨基酸的能力，然而，学术界对此相应的分子基础知之甚少。基于我组在研究AtGLR功能及根系发育机理中所积累的初步成果，本项目拟对20个AtGLR突变体的根系生长表型进行针对氨基酸敏感性反应的鉴定，以筛选出参与根生长响应氨基酸的AtGLR基因，继而将运用基因克隆与表达、电生理测试、胞质Ca2+流检测、组织化学及解剖学分析等技术，对目标AtGLR进行明确的功能鉴定。课题的成果不仅从理论上将阐明某些特定AtGLR的分子功能如离子通道及其所涉及的生物学事件，而且为调控根发育与形态、改善植物生长适应能力提供有价值的分子遗传学基础。

根系形态的建成通常能随着土壤环境的变化而做出适应性的生长调整，以利于其竞争土壤中的养分、水分等。土壤中各种氨基酸的存在以及长期的生物进化，使植物具备了吸收和响应氨基酸的能力，然而，学术界对根系生长发育响应外源氨基酸的现象及其的分子基础知之甚少。为此本课题以拟南芥为模式植物，开展了相关的研究。项目实施一年，良好地完成了课题的计划。主要成果有：（一）通过对19种L-氨基酸是否影响根系生长的详细鉴定，发现其中有6种氨基酸（即Cys, Leu, Met, Tyr, Trp, Lys）较强烈地抑制野生型植物主根的生长。（二）发现并初步阐明了半胱氨酸（Cys）抑制主根生长的生理学表型及其机理。（三）精确地鉴定出了Leu、Lys、Met抑制野生型植物主根生长的最低浓度。（四）通过大量的植物主根生长的表型筛选，发现了某些特定的谷氨酸受体基因(AtGLRs)很可能参与了主根生长响应Leu或Lys或Met，为将来深入研究根系响应外源某特定氨基酸的分子机理奠定了重要的基础。（五）鉴定、发现了五种D-氨基酸(即D-Ala, D-Agr, D-Lys, D-Pro, D-Ser)明显抑制野生型植物主根生长及其作用的最低浓度，为进一步筛选和鉴定谷氨酸受体基因是否参与根系响应外源D-氨基酸的机制奠定了重要的基础。（六）初步发现了三种L-氨基酸（即Leu, Lys,Met）影响植物根毛生长发育的表型。总之，根据现有的研究文献检索结果，上述本项目的成果目前在国内外尚未见报道，此为本课题组今后的相关研究工作创造了国内外的挑战机遇。 . 此外，在本课题经费的资助下，课题组培养在读硕士生和博士生各2名（预计于2014-2016年毕业答辩）。课题组1人次应邀参加了在温哥华举行的相关国际学术会议并做大会报告。2篇SCI论文预计在2014年投稿发表。