Poster: Temperature Responses

Abs # 176: Enhanced seed yield under heat stress at reproductive stage in Arabidopsis thaliana by overexpressing peroxisornal ascorbate peroxidase gene from barley

Presenter:	Takabe, Tetsuko , h44854a@nucc.cc.nagoya-u.ac.jp
Authors	Takabe, Tetsuko  (A)   Takamatsu, Aya  (A)   Shi, Weiming  (A)   Ueda, Akihiro  (A)   Takabe, Teruhiro  (B)   Tanaka, Yoshito  (B)   Egawa, Yoshinobu  (C)
Affiliations:	(A): Nagoya University (B): Meijo University (C): Okinawa JIRCAS

We have previously reported the enhanced thermotolerance at vegetative stage in Arabidopsis thaliana by overexpressing peroxisormal ascorbate peroxidase gene (HvAPX1) from barley (W.M. Shi et al. Gene 273: 23-27, 2001). In the present study, we examined the thermotolerance at reproductive stage in the transgenic plants. It was found that HvAPX1 gene is expressed in not only leaves but also flowers. HvAPX1 protein was also detected in both leaves and flowers by Western blotting using antibody against barley peroxisomal APX. We homogenized and fractionated organelle of the transgenic plants. HvAPX1 protein was detected in peroxisomal membrane fractions. We found that the seed yield was increased twice compared to that of WT under high temperature during reproductive stage. We examined the activity of catalase and APX in both leaves and flowers in WT and the transgenic plants. Catalase was inhibited in leaves by heat treatment (37 degree, 9 hr) while it was not inhibited in flowers. APX activity was not significantly changed in leaves of both WT and the transgenic plants by heat treatment. But, APX activity was gradually increased in flowers by heat treatment. So, these data suggested that peroxisomal APX is important to scavenge hydrogen peroxide when catalase is inhibited by heat stress. It seems that thermotolerance of sourse organ (leaves) also contributes to the enhanced seed yield under heat stress at reproductive stage of the trangenic plants.