The small GTPases of Rop/Rho family is central regulators of important cellular processes in plants. Tobacco small G protein gene NtRop1 has been isolated; however, its roles in stress responses were unknown. In the present study, the genomic sequence of NtRop1 was cloned, which has seven exons and six introns, similar to the Rop gene structure from Arabidopsis. The NtRop1 gene was constitutively expressed in the different organs whereas the other six Rop genes from tobacco had differential expression patterns. The expression of the NtRop1 gene was moderately induced by methyl viologen, NaCl, and ACC treatments, but slightly inhibited by ABA treatment, with no significant induction by NAA treatment. The transgenic Arabidopsis plants overexpressing the NtRop1 showed increased salt sensitivity as can be seen from the reduced root growth and elevated relative electrolyte leakage. The hydrogen peroxide production was also promoted in the NtRop1-trangenic plants in comparison with wild type plants. These results imply that the NtRop1 may confer salt sensitivity through activation of H2O2 production during plant response to salt stress.
CAO YangRong1,2, LI ZhiGang1,2, CHEN Tao1,2, ZHANG ZhiGang1, ZHANG JinSong1 & CHEN ShouYi1 1 National Key Lab of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China
Tocopherols synthesized exclusively by photosynthetic organisms are major antioxidants in biomembranes.In plants,tocopherol cyclase(TC/VTE1) catalyzes the conversion of 2,3-dimethyl-5-phytyl-1,4-benzoquinone(DMPBQ) to γ-tocopherol.In the present study,OsVTE1,which encodes a rice tocopherol cyclase ortholog,was cloned and characterized.OsVTE1 was induced significantly by abiotic stresses such as high salt,H2O2,drought,cold and by the plant hormones ABA and salicylic acid.The tissue-specific expression pattern and OsVTE1-promoter GUS activity assay showed that OsVTE1 was mainly expressed in the leaf,and also could be detected in the root,stem and panicle.Compared with control plants,transgenic plants with OsVTE1 RNA interference(OsVTE1-RNAi) were more sensitive to salt stress whereas,in contrast,transgenic plants overexpressing OsVTE1(OsVTE1-OX) showed higher tolerance to salt stress.The DAB in vivo staining showed that OsVTE1-OX plants accumulated less H2O2 than did control plants.
