Physiological And Molecular Mechanism Of OsRACK1 Resistance To Drought / Salt Stress

Drought and salt stress are the important environmental factors affecting plant growth and development. It was proved that rack1 mutant had strong drought tolerance and salt stress Arobidopsis RACK1 was defined as a negative regulator of ABA responses. Use the materials of wide type、interference RACK1 plants 3-1and 4-2-、anti-sense expressing RACK1 plants 676 and over-expressing RACK1 plants 738 and 749, were constructed by our laboratory,we focused on the function of RACK1 in the response to drought and salt stress by measuring plant physiology and microbiology methods, to probe into the physiological and molecular mechanism of RACK1 protein in drought and salt stress. The main results were as followed:1. By the treatment of 20%PEG and 2% NaCl, the interference and anti-sense RACK1 expressing plans have higher Pn、Gs、Tr、relative water content、SOD、POD、CAT and endogenous ABA content, the wide type in the middle and the over-expressing plant in the minimum. The over-expressing RACK1 plants ave higher Pn、Gs、Tr、relative water contents SOD and endogenous ABA content. The interference and anti-sense expressing RACK1 plants have superior photosynthetic efficiency than the wide type, the over-expressing RACK1 plants have inferior photosynthetic efficiency than the wide type. The interference and anti-sense expressing RACK1 plants have the opposite outcome. The over-expressing RACK1 plants increase the slowest speed of ABA endogenous content, so the stomatal closure degree is lower and easier to loss water under the stress than the wide type. The results were in accordance with the higher water loss and the lower relative water content.2. The interference and anti-sense RACK1 expressing plants have lower MDA than wide type and over-expressing plants, the over-expressing plant in the maximum. The interference plants 3-1 and 4-2 have low water loss rates than wide type, anti-sense expressing plants have no significant difference with control, the over-expressing plants 738 and 749 have high water loss rates than the wide type. The interference and anti-sense expressing RACK1 plants have the lighter membrane lipid oxidation degree and the higher antioxdant enzyme activity, the ability to clean the oxidative damage is better, so the interference RACK1 plants have the better drought resistance and salt resistance.3. Under the treatment of simulation drought and salt stress, the interference and anti-sense expressing RACK1 plants have higher NCED5 expression than the wide type, the over-expressing RACK1 plants have the significant lower NCED 3 and 5 expression than the wide type. These results were in accordance with endogenous ABA content results. The interference RACK1 plants have higher ABA response genes expression.4. ABA response genes include of OsABI5、OsLEA3、OsLIP9、and OsRAB16A. The wide type expression in the middle, the over-expressing RACK1 plants in the low. It was suggested that RACK1 negatively regulated ABA signaling pathway induced by the drought and salt stress.According to the above results, it was suggested that OsRACKl have the same function of AtRACKl. OsRACK1 was involved in ABA signaling pathway and was a negative regulator of ABA responses. OsRACK1 negatively regulated the drought-resistance and salt-resistance in rice plants.The increase of endogenous ABA content caused by drought and salt stress lead to the down regulation expression of OsRACK1.