Isolation And Functional Characterization Of Rice Stress-Related Genes

Rice is not only the most important crop in the world,especially for China,but also a promising model plant for plant molecular and functional genomics research.Abiotic stress,such as drought,salt,and low temperature,frequently influences rice growth, development,even survival.It becomes more and more urgent to improve rice tolerance to these abiotic stresses.In this research,More than 20 stress-responsive genes were overexpressed in rice Zhonghua 11(Oryza sativa L.ssp japonica),and the stress tolerance or abscisic acid(ABA) sensitivity of the transgenic plants were tested. Transgenic lines of four genes showed enhanced tolerance to drought,salt,or cold stress, and these genes and materials will be useful for for rice stress tolerance improvement in the future.The main results are as follows:1.Twenty-three genes that are stress-inducible in cDNA microarray analysis were construted for over-expression.The stress-induced expression and the over-expression level of these genes were checked by Northern or real time-PCR analysis.Drought tolerance of transgenic plants was tested in the field under rainoff shelter.Transgenic plants of one gene,named OsbZIP23,showed significantly enhanced drought tolerance,and this gene was selected for functional characterization.2.OsbZIP23 is a stress-related transcription factor with strong transactivation activity in yeast and the OsbZIP23-GFP fusion protein was located in nucleolus of rice. OsbZIP23 can be induced by drought,salinity stress and ABA,PEG treatment,but not by low temperature or other hormones,such as JA,SA and 2,4-D.and it has a high expression level in leaves.3.Stress testing suggested that overexpression of OsbZIP23 can enhance tolerance to drought and high salinity stresses and the OsbZIP23 overexpressors also showed hypersensitve to ABA at germination or post-germination stage.4.OsbZIP23 mutation led to high salinity sensitivity and ABA insensitivity.5.By expression profiling analysis using DNA chip,many genes related to osmotic adjustment,cell membrane stability and detoxification were found to be up-regulated in the OsbZIP23-overexpressing transgenic plants,but down-regulated or not changed in the mutant line. 6.To characterize stress-responsive rice genes of CIPK family,an important protein kinase family showing diverse roles in responses to stresses in Arabidopsis,all the 30 members of CIPK family in rice genome were checked for their expression levels under drought, high salinity,and low temperature stresses,and ABA and PEG treatments.Results suggest that 20 genes are induced by at least one type of stress or treatment.7.Three genes(OsCIPK03,OsCIPK12 and OsCIPK15 that is strongly induced by cold, drought,and salt respectively) were overexpressed in rice for stress tolerance test. Results suggest that OsCIPK03,OsCIPK12,and OsCIPK15 can enhance low temperature,drought,and salt stress tolerance respectively.8.Increased proline and soluble sugar contents were detected in the OsCIPK03 and OsCIPK12 transgenic plants under stress conditions.Proline synthesis and transportation genes were highly expressed in the OsCIPK03 and OsCIPK12 transgenic plants. OsCIPK15 is highly expressed in root;however,no significant difference in Na~+,K~+ content was detected between OsCIPK15 overexpressor and WT after salinity stress.