小麦小分子RNA TaMIR1118及其靶基因钙调素TaCaM2模块介导植株抵御低氮逆境分子机理

The small molecule RNAs (microRNAs) in plant species play critical roles in mediating plant responses and tolerance to diverse abiotic stresses through regulating the posttranscription and translation of the target genes. Previously, we have confirmed that a wheat miRNA member TaMIR1118 responds to N deprivation and comprises a regulating module TaMIR1118/TaCaM2 with its important target genes encoding camodulin (TaCaM2-1~TaCaM2-3). In this current project, we will further investigate the Ca2+-specific signature regulated by the module of TaMIR1118/TaCaM2 and elucidate the the inner relations between the expressions and subcellular locations of various Ca2+ transportation genes with this calcium ion signature. By using microarray analysis, we will identify the specific transcritome and the corresponding gene network regulated by TaMIR1118/TaCaM2 module. Furthermore, a subset of important genes identified in the gene network that are involved in regulating plant N use efficiency will be subjected to functional analysis in tolerating P deprivation through gene transformation approach. Together, our current project aims to systematically understand the Ca2+-specific signature, transcriptome, and gene network regulated by the TaMIR1118/TaCaM2 module, on which to understand the molecular mechanism how this module to mediate plants to respond and tolerate N deprivation from the miRNA-mediation pathway and to provide novel theoretical basis for generating wheat and other crop germplasms with high N use efficiency.

植物种属小分子RNA在转录后和翻译水平上对靶基因进行调节，在调控植株应答和抵御非生物逆境中发挥重要作用。本项研究以项目组前期鉴定的对低氮逆境呈明显应答小麦小分子RNA成员TaMIR1118及其作用靶基因钙调素编码基因TaCaM2-1~TaCaM2-3构建的TaMIR1118/TaCaM2模块为基础，揭示该模块特异调控的钙信号标签特征，阐明介导细胞及亚细胞水平Ca2+转运基因表达及细胞、亚细胞定位及其与特定钙信号标签的内在联系；采用基因芯片杂交技术，阐明该模块特异调控的转录谱和基因网络；进一步采用遗传转化技术对该网络中重要氮效率调控基因抵御低氮逆境功能进行鉴定。本项研究旨在系统阐明TaMIR1118/TaCaM2模块特异调控的钙信号标签特征、转录谱和基因网络，从miRNAs介导途径角度，解析该模块介导小麦植株应答和抵御低氮逆境分子机理，为今后小麦氮高效遗传改良提供理论依据。

植物种属小分子RNA通过在转录后水平对作用靶基因调节，在介导植株抵御各种非生物逆境中发挥着重要功能。本课题以对低氮逆境应答的小麦TaMIR1118/ TaCaM2模块调控钙信号标签特征、介导细胞及亚细胞Ca2+转运基因表达模式、调控转录谱及介导植株抵御低氮逆境功能进行了研究。课题取得下述结果。 .1. TaMIR1118/TaCaM2模块应答低氮表达模式.TaMIR1118在根叶中均呈典型低氮诱导及复氮下调表达模式，TaCaM2对低氮和复氮处理的表达模式与TaMIR1118相反，呈典型低氮下调和复氮诱导上调表达模式。表明TaMIR1118在转录后水平对TaCaM2进行调节，参与植株对低氮逆境响应过程。.2. 模块介导低氮诱发钙信号标签传递特征.以At-pHluorins 载体遗传转化对照）、正义表达 TaMIR1118株系和敲除TaCaM2株系为材料，对转基因系 GFP 信号进行了实时检测。TaMIR1118/TaCaM2模块对胞质钙信号振荡产生较大影响。与对照相比，转化系胞质钙信号振幅增大（13.60~20.12%），振频缩短（20.30~26.00%）。CaM2家族成员在调控胞质钙信号振幅和振频中存在冗余效应。 .3. 模块调控转录谱特征.对低氮处理对照、超表达TaMIR1118株系（Sen 1118）和下调表达TaCaM2株系（Anti-CaM）根叶转录谱研究表明，Sen 1中1256个基因表达上调，863个基因表达下调；Anti-CaM中1386个基因表达上调，1027个基因表达下调。上调基因归属受体蛋白、信号转导、转录调控、激素信号、生化代谢、逆境响应、氧化防御、蛋白合成和核酸代谢等基因家族。 .4. 模块及下游氮胁迫响应基因功能解析.对TaMIR1118/TaCaM2模块及其调控下游基因TaNBP1、TaZFP593;l和TaARR1以及与TaMIRR118协同作用小麦种属miRNA成员TaMIR2275、TaMIR444a和TaMIR408介导植株抵御低氮功能进行了研究。 .课题关键数据：获得了TaMIRR1118/TaCaM2模块转录、介导特定钙信号传递、调控下游转录谱、下游关键氮响应基因调控植株氮效率等方面关键数据。 .课题科学意义：揭示了TaMIR1118与其作用靶基因应答低氮逆境分子特征及模块介导植株抵御低氮逆境分子机理。