Poster: Oxidative Stress

Abs # 112: Roles of chloroplast glutamine synthetase on the tolerance for high temperature and salt stresses

Presenter:	Yamamoto, Atsuko , d6020009@ccmailg.meijo-u.ac.jp
Authors	Yamamoto, Atsuko  (A)   Aoki, Kenji  (A)   Hibino, Takashi  (A)   Tanaka, Yoshito  (A)   Suzuki, Shigetoshi  (A)   Takabe, Teruhiro  (A)
Affiliations:	(A): Meijo University

Under stress conditions such as drought and high salinity, stomatal closure triggered by abscisic acid limits CO2 supply to the leaf leading to overreduction of the photosynthetic electron transport chain. Therefore, enhancement of the enzyme activity involved in active oxygen scavenging systems may be a potent strategy to increase salt tolerance. An alternative strategy to cope with oxidative damage under salt stress might be the suppression of active oxygen production. Photorespiration may function as a possible route for the dissipation of excess light energy or reducing power. Although photorespiration includes many metabolic steps which are performed across chloroplasts, mitochondria and peroxisomes, several studies suggest that the rate-limiting step is the reassimilation of ammonia catalyzed by chloroplastic glutamine synthetase (GS2). Previously, we have demonstrated that a transgenic rice plant overexpressing GS2 constitutively had increased photorespiration capacity and increased tolerance to high salinity and high tempeerature. In the present study, we isolated GS2 gene from a betaine accumulating mangrove, Avicennia marina and expressed in E. coli. We constructed the vectors for the expression of full length- and C-terminal deleted-mangrove GS2 as well as full length rice GS2. These genes were exressed in E. coli and purified. Thier functional properties were examined. Although the homology of amino acid sequence deduced from the nucleotide sequence is very high, the enzymatic properties between them were different. We also contructed the transgenic Arabidopsis using a stress inducible promoter RD29. Effects of high temperature and high salinity on WT and transgenic plants were examined.