Regulation of MAP kinase signaling cascade by microRNAs in Oryza sativa.

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 Oryza sativa. Using in silico 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 in silico 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.