Physiological Function of AtGSTU25 in Arabidopsis thaliana
Date Issued
2012
Date
2012
Author(s)
Jan, Wun-Shiou
Abstract
Glutathione S-transferases (GSTs; EC 2.5.1.18) constitute a superfamily containing 55 members in Arabidopsis thaliana and biochemically can catalyze the nucleophilic addition of the thiol of the reduced form glutathione to a wide variety of electrophilic substrates. The best known study was GSTs mainly in relation to their role in the detoxification of herbicides and to protect organisms against oxidative stress. In addition to enzymatic function, only a few GSTs have been reported to serve as signaling molecule to influence plant growth and development. In our previous study, atgstu17 mutants exhibited drought and salt tolerant phenotypes when subjected to abiotic stress treatment. The mechanism causing the phenotype of atgstu17 can be explained mostly by the combined effect of elevated contents of both glutathione and abscisic acid. We wonder whether AtGSTU25 having highest catalytic activity in vitro when silenced could exhibit similar phenotype as that of atgstu17. In this study, AtGSTU25 T-DNA knockout mutant (Salk_042213) was obtained from ABRC and the hemizygote mutants carried empty seeds in siliques which produced wild type and hemizygote plants but lack of homozygote knockout mutants. The lethal phenotype of Salk_042213 mutants were reconfirmed after 3 consecutive generations. In the complementary experiment by introducing the AtGSTU25 cDNA into AtGSTU25 hemizygote mutants, we still couldn’t get the AtGSTU25 homozygote mutant indicating the lethal phenotype was attributed to another locus. We generated AtGSTU25 overexpressors and RNAi knock down mutants for further study. Expression of AtGSTU25 is mainly in the root system and apical part of leaf blade. Localization study using protoplast revealed the cytoplasm distribution of 35S:AtGSTU25-GFP. With respect to the oxidative stress tolerance, AtGSTU25 overexpressor and knockdown lines didn’t show difference from wild type plant indicating maybe AtGSTU25 play no role in cell detoxification. RNAi mutants of AtGSTU25 exhibited lower germination rate than wild type plants under salt stress condition. RNAi mutants of AtGSTU25 also exhibited earlier bolting time and earlier senescence of leaf tissue. Taken together, we inferred that The AtGSTU25 would play roles in regulating the seed germination and root elongation under salt stress condition, and delay bolting time and repress senescence of leaf tissues.
Subjects
Glutathione S-transferases
glutathione
oxidative stress
senescence
bolting time
Type
thesis
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