Of Arabidopsis Atrack1 Protein Mechanism Of Response To Drought Stress Signal

RACK1 is a versatile scaffold protein which can bind numerous signaling molecules and plays critical roles in multiple developmental processes in mammals. However, at present we know little about RACK1 in plants. In this study, we focused on the possible roles of RACK1 in the responses to soil drought and possible interactions with G protein-mediated signal transduction pathway, using corresponding Arabidopsis single and double mutants, i.e., rack1 agb1-2, rack1, agb1-2, rack1 gpa1-4, gpa1-4, 35s: RACK1 and their wild type Col. The possible functions of ATHK1 in plant responses to drought were also investigated. The major results are showed as followings:1. Significant differences in drought tolerance were observed among different genotypes, as compared to wildtype, Columbia (Col). Mutants rack1 agb1-2, rack1, agb1-2 showed the higher drought tolerant than any other mutants, and RACK1-overexpressing mutant was least tolerant to drought.2. The water loss rates of rack1 agb1-2, rack1 and agb1-2 were significantly lower than those of Col, rack1 gpa1-4, gpa1-4 and 35s: RACK1 .3. Under soil drying condition, the leaf water potential and stomatal conductance of all genotypes investigated decreased gradually with the progress of soil drying. The leaf water potential of rack1 agb1-2 and agb1-2 was always higher than those of other five genotypes, 35s: RACK1 was always the lowest. A significant difference in stomatal conductance was observed among different genotypes in responses to soil drying and rack1 agb1-2 was always highest among them.4. The ABA content of leaves increased gradually with the progress of soil drying. The rack1 agb1-2 increased most rapidly among seven genotypes.5. The drought tolerance of mutant athk1 was significantly lower than that of rack1 and the drought tolerance of double mutant rack1 athk1 was almost similar to that of athk1 mutant.According to the above results and other reports, it was suggested that AtRACK1, G protein and ATHK1 played important roles in plant drought tolerance.The result also indicated that AtRACK1 and G protein may act in a parallel fashion. ATHK1 and AtRACK1 may act in the same signal transduction and ATHK1 may act at the downstream of At RACK1.