Functional Analysis Of Myb-Type Transcription Factor Osmyb91in Rice Growth And Stress Tolerance

As sessile organisms, plants are confronted with much biotic and abiotic stress over their whole life. Therefore, plants have evolved a number of different mechanisms to respond and to adapt to abiotic stresses for their survival. Plant hormones, transcription factors and epigenetics are playing essential roles in resisting to different stresses. However, the regulatory mechanisms of these responses are not fully understood.In the current study, we discussed the function of a MYB transcription factor OsMYB91and the role of ABA and epigenetics on it, which may provide solid foundations for further study about the relationship among transcription factors, plant hormones and epigenetics in resist to salt stress.The main results we got through the combination of many methods such as sequence analysis, molecular cloning, genetic transformation and stress treatments are as follows:1.OsMYB91expressed in most organs/tissues in wild type. Besides, the expression of OsMYB91was induced by various abiotic stresses(salt、drought、cold、heatshock) and exogenous plant hormones(ABA、SA、NAA、JA、6-BA).2. Salt stress led to rapid removal of DNA methylation from the promoter region and rapid changes of histone modifications in the locus.3.OsMYB91was localized in the nucleus and had transcription activation activity in yeast.4. Over-expression of OsMYB91reduced plant growth and enhanced tolerance to salt stress. The analysis revealed much high transcript levels of SLR1in the over-expression plants grown under normal conditions compared to wild-type. SLRl that encodes DELLA protein mediates the GA pathway which controls plant growth under normal condition and improves the activity of ROS scavenging enzymes such as SOD and catalase under stresses.5. Over-expression of OsMYB91altered sensitivity of seed germination and growth to ABA, high endogenous ABA levels in OsMYB91over-expression lines might contribute to the enhancement of the resistance to salt stress.6.OsMYB91-overexpression plants accumulated less H2O2and MDA under salt stress indicating that the overexpression of OsMYB91improves the ROS scavenging capabilities by increasing the enzyme activities of POD and CAT. In summary, our data suggest that chromatin modification change is an early step in salt-stress induced expression of OsMYB91that encodes a transcription activator. Increased expression of the gene leads to higher expression of the SLR1gene and accumulation of ABA, the interaction of which controls plant growth rate and salt stress tolerance. While the increased ABA may benefit to produce more material osmosis, the high SLR1level promotes to the synthesis of many ROS scavenging enzymes. All these together enhanced the rice tolerance to salt stress.