Athk1 The Molecular Mechanism Of The Response To Drought Stress In Plants

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. In this study, we focused on the function of ATHK1 in the response to drought stress and its possible interaction with G protein-mediated signaling pathways and with RACK1 using null mutants and double mutants of ATHK1 protein, G protein and RACK1 protein. The main results are as follows:1. Significant differences in morphology and drought tolerance were observed among different genotypes investigated. agb1-2 and rack1 mutants were the most tolerant and athk1 mutant the least tolerant to soil drying. The morphological characters and drought tolerance of athk1gpa1-4,athk1agb1-2 and athk1rack1 double mutants were almost the same to those of athk1 mutant.2. During soil drying period, leaf water potential and stomatal conductance decreased gradually with the progress of soil drying. However, agb1-2 and rack1 mutants were not so sensitive to soil drying, as a result, their leaf water potential and stomatal conductance did not decreased significantly as compared with other mutants and wildtype. athk1 mutant showed the most sensitive to soil drying in terms of leaf water potential and stomatal conductance. Upon rewatering, leaf water potential and stomatal conductance of all mutants and wildtype recovered to control levels rapidly.3. Great differences were also detected in water loss of detached leaves among different genotypes. athk1 mutant showed the highest water loss rate and agb1-2 and rack1 mutants the lowest. The water loss rates of all double mutants investigated is similar to that of athk1 mutant.4. The leaf ABA contents of all mutants are increased qucikly and significantly after soil drying. At the 24th days of soil drying treatment, the leaf ABA contents of agb1-2 and rack1 mutants were significantly higher than those of any other mutants and wildtype, and mutant athk1 had the lowest ABA content.According to the above results and other reports, it was suggested that ATHK1 protein may act as an osmosensor of the drought stress signal, and interacts with G protein and RACK1 protein respectively during the process of drought signal transduction, and ATHK1 protein works dowmstream of G protein and RACK1 protein.