Functional Analysis of Rice Actin Depolymerizing Factor OsADF2 and OsADF11 by Heterologous Expression in Arabidopsis

Actin Depolymerizing Factors (ADFs) are small actin-binding proteins in cytoskeleton remodeling in cells. Recently, ADFs were reported to play a role in plant growth, development, cell division, signal transduction and pathogen resistance. However the functions of rice ADFs (OsADFs) under abiotic stress still remained to explore. In this thesis, we took heterologous gene expression approach to overexpress rice OsADF2 and OsADF11 in Arabidopsis, and observed the phenotype difference between transgenic and wild type plants under normal growth and abiotic stress. The phenotype of OsADF2 and OsADF11 transgenic plants showed bigger leaves size than Col-0, moreover, the bolting time and flowering time was earlier. The germination rate of transgenic plants had no difference compared to wild-type under normal condition while the germination rate of transgenic plants was faster after treatment with 150 mM NaCl. We also transferred the 5-day old and 10-day old seedlings to the 150 mM NaCl medium and found that the root growth and survival ratio of transgenic plants were both higher than wild-type. Next we grown 21-day old OsADF2, OsADF11 transgenic and wild-type plants under drought, salt and cold stresses, and OsADF2 and OsADF11 transgenic plants tended to be drought tolerance while injury tissue occurred in OsADF11 transgenic plant under cold treatment. Using non-destructive infrared thermography camera recorded the leaf temperature change under salt stress condition, the result showed that no obvious differences were found between transgenic and wild-type plants under normal condition. However OsADF11 transgenic plants showed higher leaf temperature compared to wild-type but not OsADF2 after treatment with 200 mM NaCl. In addition, to understand the subcellular localization of rice OsADFs, we used maize ubiquitin promoter to express rice OsADFs-GFP fusion protein through rice protoplast mediated transformation. The result showed that OsADF3-GFP and OsADF11-GFP were located in the nucleus and cytosol, and OsADF2-GFP was located in thel nucleus, the cytosol and also in chloroplasts. OsADF1, OsADF4, OsADF5 and OsADF6 were located in the chloroplasts. Taken together from above results, our study implied that rice OsADF2 and OsADF11 maybe involve in the plant response to drought and salt stress.