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University of Tsukuba (2002)

Important roles of drought-and cold-inducible genes for galactinol synthase in stress tolerance in arabidopsis thaliana

Taji, Teruaki ;

Titre : Important roles of drought-and cold-inducible genes for galactinol synthase in stress tolerance in arabidopsis thaliana

Auteur : Taji, Teruaki ;

Grade : Ph. D. in Science 2002

Université de soutenance : University of Tsukuba

Résumé
Raffinose family oligosaccharides (RFO), raffinose and stachyose, accumulating during seed development are thought to play some roles in desiccation tolerance of seeds. However, functions of RFO in drought tolerance of plants have not been elucidated. here, I examined the functions of RFO in Arabidopsis thaliana plants under drought and cold stress conditions based on the analyses of function and expression of genes involved in RFO biosynthesis. Sugar analysis showed that drought-, high-salinity- and cold-treated Arabidopsis plants accumulate a large amount of raffinose and galactinol, but not stachyose. Raffinose and galactinol were not detected in unstressed plants. This suggests that raffinose and galactnol are involved in the tolerance to drought, high-sallllinity and cold stresses. Galactinol synthase (GolS) catalyzes the first step in the biosynthesis of RFO from UDP-galactose. I identified three stress-responsive GolS genes (AtGolSl, 2 and 3) among 7 Arabidopsis GolS genes. AtGolSl and 2 were induced by drought and high salinity stresses but not by cold stress. By contrast, AtGolS3 was induced by cold stress but not by drought or salt stress. All the GST fusion proteins of GST-AtGolS1, 2 and 3 expressed in Escherichia/coli had galactinol synthase activities. Overexpression of AtGolS2 in transgenic Arabidopsis caused an increase in endogenous galactinol and raffinose, and showed reduced transpiration from leaves to improve drought tolerance. These results show that stress-inducible galactinol synthase plays a key role in the accumulation of galactinol and raffinose under abiotic stress conditions, and that galactinol and raffinose may function as osmoprotectants in drought-stress tolerance of plants.

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