The Roles Of LeftsH6 And Thftsh8 In The Stress Tolerance Of Arabidopsis Thaliana And Thellungiella Halophila

FtsH, encoded by the ftsH gene, belongs to the AAA protease family. FtsH, which is an ATP and Zn2+-dependent part-time protein, have the ATPase activity, proteolytic activity and the class of molecular chaperone activity. In the plants, molecular chaperones can prevent the protein precursor accumulate and assist the protein cross membrane shift, form the complex with not folded protein to maintain its shift ability, maintain the normal folding condition of the protein, promote the degeneration of the wrongly folding protein, stabilize the multi-peptide chain and prevent the protein deactivation under the stress condition.In prokaryotes, FtsH proteinase are mainly stress induction. In higher plant, FtsH proteinase are closely related to light stress, low temperature as well as plant disease, but the plant FtsH family members are multitudinous, has the different response characteristic to the different adverse circumstance stesss, for example, the expression of Arabidopsis thaliana AtftsH1, AtftsH2 and AtftsH5 is light dependent, while LeftsH6 is a typical heat-inducible genes. In this paper, the researches are studied from the following two respects: 1 The stress resistance of LeftsH6 in Arabidopsis thalianaLeftsH6 is derived from tomato, which is a typical heat-inducible gene. The expression of LeftsH6 is not induced by cold, drought, high salinity and high light stress conditions. Over-expression of this gene can lead to the normal vegetative growth of tomato, but the barriers to reproductive growth such as the high pollen abortion and producing fruit abnormally. We constructed the LeftsH6 over-expression vector and transformed it into the wild-type Arabidopsis thaliana, extracted genomic DNA of the transformants to test by PCR. The results showed that the gene have been successfully transformed into the wild-type Arabidopsis thaliana. We used the transformants for the heat resistance experiment and high temperature growth experiment. the results did not show any phenotype, showing that LeftsH6 gene did not affect the heat resistance of Arabidopsis thaliana.2 The stress resistance of Thftsh8 in Thellungiella halophilaIn Arabidopsis thaliana, AtFtsH2 and AtFtsH8, AtFtsH1 and AtFtsH5 are closely related pairs of genes, and spatial expression pattern of AtFtsH1, AtFtsH2, AtFtsH5 and AtFtsH8 are similar. It has been shown that AtFtsH2 (VAR2) and AtFtsH5 (VAR1) involved in the light protection and the process of thylakoid development, the mutations of two genes would lead to variegated leaves and the increase of the sensitivity to light. But the T-DNA insertion mutants of AtftsH1, AtftsH6 and AtftsH8 did not have the above-mentioned phenotypes. We constructed the Thftsh8-RNAi expression vector and transformed it into the wild-type Thellungiella halophila, extracted the RNA of Thftsh8-RNAi lines for Real-time PCR test. The results showed that the expression of Thftsh8 in Thftsh8-RNAi lines reduced, but the reduced levels in the different lines are different. Thftsh8 is a low-temperature-induced gene, after experiencing the natural conditions in winter, line 3 of Thftsh8-RNAi lines showed obvious yellow phenotype, but line 2 and line 4 did not show yellow phenotype. Compared with wild-type, the leaf color of Thftsh8-RNAi lines was weaker, chlorophyll measurement results consisted with the results of the yellow phenotype.