Regulation of MAP kinase signaling cascade by microRNAs in <i>Oryza sativa</i>

Mitogen activated protein kinase (MAPK) pathway is one of the most conserved signaling cascade in plants regulating a plethora of cellular processes including normal growth and development, abiotic and biotic stress responses. The perception of external cues triggers the phosphorylation of three tier MAPKKK-MAPKK-MAPK cascade which finally modifies a downstream substrate thereby regulating the cellular processes. Whereas, the transcription regulation by MAPKs, mediated through their substrates is well studied in plants, the transcription and post-transcriptional regulation of the MAPK genes are poorly understood. Previous studies from the animals systems suggested the miRNAs regulate the post-transcriptional regulation of MAPK transcripts. Here we attempt to unravel the post-transcriptional regulation of MAPKs by miRNAs in model crop plant <i>Oryza sativa</i>. Using <i>in silico</i> tools, we predict the miRNAs for 98 out of 99 MAPK transcripts. The predicted miRNAs were validated for the biological relevance of their function. The inverse correlation between relative transcript levels between the MAPKs and their predicted miRNAs validated the <i>in silico</i> prediction. Taken together, this report demonstrates the significance of miRNAs in regulation of the MAPK pathway in plants with a new direction to study the plant signaling molecules.

丝裂原活化蛋白激酶（mitogen-activated protein kinase, MAPK）通路是植物中最为保守的信号级联反应之一，可调控包括正常生长发育、非生物与生物胁迫应答在内的众多细胞进程。对外界信号的感知会触发三级MAPKKK-MAPKK-MAPK级联的磷酸化反应，最终通过修饰下游底物来调控细胞进程。尽管植物中由MAPKs通过其底物介导的转录调控已被广泛研究，但MAPK基因自身的转录及转录后调控机制却鲜有深入解析。此前动物系统的研究表明，微小RNA（microRNA, miRNA）可对MAPK转录本进行转录后调控。本研究旨在解析模式作物水稻（Oryza sativa）中miRNAs对MAPKs的转录后调控机制。借助计算机模拟（in silico）工具，我们对99个MAPK转录本中的98个完成了miRNA靶向预测。随后针对预测得到的miRNA开展了功能生物学相关性验证。MAPKs与其预测靶向miRNAs的相对转录水平呈负相关，这一结果验证了计算机模拟预测的准确性。综上，本研究证实了miRNAs在植物MAPK通路调控中的重要作用，为植物信号分子的研究提供了全新方向。