Functional Analysis Of The Gene Involved In The Regulation Of Salt/Drought Stress Responses In Arabidopsis

Expression of the DSR1 gene encoding a unkown protein was found to be induced by salt and drought stresses by using gene expression microarray analysis data. However, it is unclear whether the DSR1 gene plays important roles in the regulation of the responses of Arabidopsis plants to salt and drought stresses.To clarify the role of the DSR1 gene in salt/drought-stress responses, we studied the characteristics of responses of wild-type Arabidopsis and mutants dsr1-1, dsr1-2 to salt and drought stresses. The results are as follows:1. Under different concentrations of NaCl stress conditions, the survival rate of dsr1-1 mutant is significantly higher than that of wild type. In 175mM NaCl conditions, survival rate of the mutant dsr1-1 was 40% higher than that of the wild type; in germination rate experiment, in 125mM NaCl conditions, the germination rates of mutants dsr1-1, dsr1-2 were higher than the wild type 21.62% and 27.03%, respectively; under vertical culture experiment conditions of 100mM of NaCl, the root length of mutant dsr1-1, dsr1-2 was about 1.5cm longer than that of the wild type, Fresh weight of mutant was approximately 4.5mg/5plants higher than that of the wild type. suggesting that the mutants dsr1-1, dsr1-2 are more resistant to salt stress than the wild type.2. QRT-PCR analysis of salt stress-related gene expression also showed that enhanced resisitance of mutants dsr1-1, dsr1-2 to salt stress may be related to the increases in expression levels of MYB2/MYC2 and their downstream targeting genes, indicating that DSR1 gene could regulate MYB2/MYC2-mediated signal transduction pathway to regulate salt stress responses.3. Under drought stress, the survival rate of mutants dsr1-1, dsr1-2 wereas significantly higher than that of wild type; and the tolerance of mutants dsr1-1, dsr1-2 to osmotic stress was more resistant to osmotic stress than the wild type, and. InUnder drought stress conditions, the levels of mutants soluble sugar and proline accumulation in mutants were significantly higher than those of the wild type, indicating that enhanced resistance of mutants dsr1-1 and dsr1-2 is assiacted with increases in the levels of soluble sugar and proline accumulationmore tolerant than wild-type to drought stress.4. QRT-PCR analysis of drought stress-related gene expression showed that enhanced tolerance of mutants dsr1-1 and dsr1-2 to drought stress may be related to increases in the expression levels of the proline synthesis gene P5CS and some stress downstream genes under drought stress.5. In the ABA germination experiments, in 5mM ABA condition, the germination rates of mutants dsr1-1 and dsr1-2 were significantly higher than the wild-type 29.73% and 32.43%, respectively, indicating responses of mutants dsr1-1and dsr1-2 to salt and drought stresses may be ABA dependent.6.In KC1, and LiCl stress experiments further confirmed enhanced salt tolerance of mutants dsr1-1, and dsr1-2 are was associated with the mechanism of ion balance to salt tolerance. In addition, mutants also showed, there is another explanation of enhanced H2O2 resistance compared with the wild type,mutants suggesting that enhanced salt/drought resistance of mutants is also assicated with oxygen scavenging mechanism.In sum, all these results show that DSR1 gene in the regulation of salt and drought stress plays an important role in the regulation of salt and drought stress responses.