Rice Rack1 Gene (osrack1,) Function In Response To Drought Stress

Drought stress is one of the most important environmental factors affecting plant growth and development,and thus the final yield.Plants have evolved in many mechanisms coping with the drought stress and many genes and their products (proteins) are involved in the responses to drought stress.Several results showed Arabidopsis RACK1 plays am important roles in plant growth and development and in the responses to environmental stress.In rice genome,two high homologus amino acid sequences have been found.However,we know little about their functions in rice.In the present study,we constructed RACK1 over-expressing and anti-sense expressing systems in rice plants (OsRACK1),and studied the possible roles of RACK1 in the responses of rice to drought stress.The main results obtained are as follows:1. We constructed OsRACK1 over-expressing and anti-sense expressing vector and transferred them into rice callus (Oryza sativa subsp. japonica cv. Nipponbare) using agrobacterium tumefaciens.After several steps of screening, we successfully obtained OsRACK1 over-expressing and anti-sense expressing rice plantlets and seeds of T1 generation.2. We firstly analyzed the roles of OsRACK1 in seed germination.The results showed the seed germination of RACK1 over-expressing rice plants was more rapidly than those of non-transgenic seeds and anti-sense expressing seeds.The soluble sugar content of germinating seeds of RACK1 over-expressing rice was higher and their contents of soluble protein and ABA were lower than those of non-transgenic seeds and anti-sense expressing seeds.3. The relative water content,contents of chlorophyll, proline,and ABA,and the activities of anti-oxidative enzymes of RACK1 over-expressing rice seedlings under treatment of 5% and 10%PEG6000 were lower than those of non-transgenic seeds and anti-sense expressing seedlings.The MDA content and electric conductivity of the former were higher than ther laters.4. The results of Real time PCRanalysis showed that there were no significant differences in DREB1 expression under drought stress and ABA treatments between different genotyps.However,under same conditions,P5CS expression of anti-sense expressing seedlings was significant higher than that of non-transgenic and RACK1 over-expressing rice seedlings.According to the above results,it was suggested that OsRACK1 negatively regulated the drought-resistance of rice plants and this regulation was,to a large extent,realted to ABA and proline biosynthesis.Of course,the detailed molecular mechanisms of OsRACK1 in the responses of rice to drought stress is worthy of further study.