The Molecular Mechanism Of Rice Ethylene Response Factor Osderfl In Drought Tolerance

Phytohormone function as signal molecules regulated a variety of developmental processes and stress responses in plants. Ethylene is one of the important hormones not only involved in plant development, such as seeds germination, root growth, and fruit rippeness, but also participated in plant biotic and abiotic stress response, like low temperature, drought, high salt and pathogen infect. It is important to elucidate the biological function of ethylene and the mechanism of ethylene signal transduction by studying the regulation mechanism of ethylene biosynthesis. Ethylene biosynthesis is modulated by many factors or regulators at both transcriptional and post-transcriptional levels. Combining the regulations at both transcriptional and post-transcriptional levels of ethylene synthesis and transduction, plant can coordinate the ethylene signal pathways and other hormone signaling pathway, keep their life and adapt various stresses. Rice is an important food crop, and studies in rice ethylene synthesis have made great progress in recent years. However, the detail regulatory mechanisms are limited that ethylene production is transcriptionally regulated in rice. In the present research, using genomic transcriptional data in the websites of rice massively parallel signature sequencing,12drought-responsive ERF genes (DERF) were identified. One of the DERF genes, OsDERF1(Os08g35240), is located in rice chromosome8. It is a novel transcriptional activator that modulates the expression of ethylene response factor (ERF) repressors, the ethylene synthesis and the drought tolerance in rice. Through analysis of transcriptional data, one of the drought-responsive ERF genes (DERF), OsDERF1, was identified for its activation in drought, ABA and ethylene precursor ACC. Transgenic plants overexpressing OsDERF1(OE) led to deduced while knockdown the expressing OsDERF1(RI) conferred enhanced tolerance to drought stress in rice seedling and tilling stages. And this regulation was supported by negative modulation in osmotic adjustment response. To elucidate the molecular basis of drought tolerance, we identified the target genes of OsDERF1using the Affymetrix GeneChip, which activated the expression of cluster stress-related negative regulators including ERF repressors. Biochemical and molecular approaches evidenced that OsDERF1at least directly interacted with the GCC box in the promoters of ERF repressors OsERF3and OsAP2-39. Further investigations showed that the expression of ethylene synthesis genes reduced in OE seedlings while enhanced in RI seedlings, thereby resulting in the changes of ethylene production. Moreover, overexpression of OsERF3/OsAP2-39suppressed the ethylene synthesis. In addition, application of ACC recovered the drought sensitive phenotype in overexpression of OsERF3transgenic lines, evidencing that the ethylene production contributes to the drought response in rice. Thus our data reveal that ERF transcriptional complex modulates drought response through controlling the ethylene synthesis, deepening our understanding of ERF protein regulation in ethylene synthesis-related drought response.In addition, in order to deepen our understanding on OsDERF1, we identified several OsDERF1interacting proteins by screening yeast expression library, one of those was a C3H2C3Ring finger protein DEIP1(OsDERF1-Interacting Protein1), the expression pattern of DEIP1was similar with OsDERF1, and it might participate in the degradation of OsDERF1. Experiments in yeast demonstrated that DEIP1could interact with OsDERF1, DEIP1and OsDERF1were both located in the nucleus.