Important roles of drought‐ and cold‐inducible genes for galactinol synthase in stress tolerance in Arabidopsis thaliana

Abstract

SummaryRaf®nose family oligosaccharides (RFO) accumulating during seed development are thought to play a role in the desiccation tolerance of seeds. However, the functions of RFO in desiccation tolerance have not been elucidated. Here we examine 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 raf®nose and galactinol, but not stachyose. Raf®nose and galactinol were not detected in unstressed plants. This suggests that raf®nose and galactinol are involved in tolerance to drought, high salinity and cold stresses. Galactinol synthase (GolS) catalyses the ®rst step in the biosynthesis of RFO from UDP-galactose. We identi®ed three stress-responsive GolS genes (AtGolS1, 2 and 3) among seven Arabidopsis GolS genes. AtGolS1 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 raf®nose, 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 raf®nose under abiotic stress conditions, and that galactinol and raf®nose may function as osmoprotectants in drought-stress tolerance of plants.

Chemical Profiling and Gene Expression Profiling during the Manufacturing Process of Taiwan Oolong Tea “Oriental Beauty”

“…It is known that various plants accumulate raffinose family oligosaccharides, such as sucrose, galactinol, and raffinose, in response to the stresses such as drought and cold. [43][44][45] Some of the transcripts responsible for the tea manufacturing process were identified as NCED, Ntdin of senescene-associated protein, and molybdenum cofactor sulfurase (Table 3), which are involved in ABA biosynthesis. ABA is well known as a plant defense-related hormone responding to environmental stresses such as drought, cold, and saline.…”

Contrasting relations between diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…Indeed, GALA was reported to be involved Ducousso et al (1996). in tolerance to drought, high salinity and cold (Pukacka and Wojkiewicz, 2002;Taji et al, 2002) in Arabidopsis thaliana. DAG2 was shown to act as a transcription factor specifically involved in the maternal control of seed germination (Gualberti et al, 2002).…”

“…In A. thaliana (Taji et al, 2002), galactinol synthase contributes to the accumulation of galactinol under abiotic stress conditions (drought, salinity and cold) and acts as osmoprotectant of the seed. In barley, the expression of ASI in germinating seeds indicates a potential role in defense against pathogens of the developing seed and embryo.…”

Contrasting relationships between the diversity of candidate genes and variation of bud burst in natural and segregating populations of European oaks

“…The functional role of these genes was investigated in studies conducted on other plants. Indeed, GALA was reported to be involved in tolerance to drought, high salinity and cold (Pukacka and Wojkiewicz, 2002;Taji et al, 2002) in Arabidopsis thaliana. DAG2 was shown to act as a transcription factor specifically involved in the maternal control of seed germination (Gualberti et al, 2002).…”