Functional analysis of the chloroplast inner envelope membrane protein Tic55

• Main Authors: Wan-chen Wei, 魏婉貞
• Other Authors: Po-Hsuan Chou
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/08107128371000177511

碩士 === 慈濟大學 === 生命科學系碩士班 === 99 === Chloroplasts are organelles found in plant cells vital for their function, including outer membrane that contain three-membrane envelope, inner membrane, and thylakoid membrane. The chloroplast has its own genome, but most of plastid proteins are encoded by the nucleus and synthesize in the cytosol. These precursor proteins with N-terminal transit peptides are post-translationally translocated into the chloroplast stroma through the protein complexes that named the Toc and Tic (Translocon at the outer/inner envelope membrane of chloroplasts). Previous studies indicate that Tic55 protein is the member of Tic complex and associate with Tic110 protein. The deduced amino acid sequence of Tic55 contains the redox-related motif that essential for protein import into the chloroplasts in pea. To investigate the biological function of Tic55 in Arabidopsis, we characterize three tic55 knockout mutants (SALK_086048, SALK_113085 and SALK_124629) obtain from the Arabidopsis Biological Resource Center (ABRC) by using genetic and biochemical aPproach. Phenotypic analysis indicates no obvious mutant phenotype found in tic55 mutant lines, when compared with wild-type. Western blot analysis showed the amount of other translocon proteins and the efficiency of chloroplast protein import are not affected by the tic55 mutations when plants are grown under standard controlled conditions. Therefore, we further analyaze the responses to different abiotic stress in tic55 mutant backgrond. Our results indicate that the tic55 mutant is not significantly more sensitive to cold and heat stress than the wild type, but has obvious effect on the mutant background in dark-induced senescence treatment. Based on the membrane fractionation, further yeast two hybridization analysis and co-immunopreciptation experiments, we demonstrated that Tic55 located in the inner membrane of chloroplasts and physically associate with a part of the translocon complex of Tic110,Tic40, and Hsp93. We propose that Tic55 functions as a member of translocon complex in inner membrane of chloroplast and may play essential role during the process of delay the leaf senescence.