Galactinol and Raffinose Constitute a Novel Function to Protect Plants from Oxidative Damage

Ayako Nishizawa,Shigeru Shigeoka,Yukinori Yabuta

doi:10.1104/pp.108.122465

Ayako Nishizawa, Shigeru Shigeoka + Show 1 more

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https://doi.org/10.1104/pp.108.122465

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Journal: Plant Physiology	Publication Date: May 23, 2008
Citations: 890	License type: CC BY 4.0

Affiliation: Kindai University

Abstract

Galactinol synthase (GolS) is a key enzyme in the synthesis of raffinose family oligosaccharides that function as osmoprotectants in plant cells. In leaves of Arabidopsis (Arabidopsis thaliana) plants overexpressing heat shock transcription factor A2 (HsfA2), the transcription of GolS1, -2, and -4 and raffinose synthase 2 (RS2) was highly induced; thus, levels of galactinol and raffinose increased compared with those in wild-type plants under control growth conditions. In leaves of the wild-type plants, treatment with 50 mum methylviologen (MV) increased the transcript levels of not only HsfA2, but also GolS1, -2, -3, -4, and -8 and RS2, -4, -5, and -6, the total activities of GolS isoenzymes, and the levels of galactinol and raffinose. GolS1- or GolS2-overexpressing Arabidopsis plants (Ox-GolS1-11, Ox-GolS2-8, and Ox-GolS2-29) had increased levels of galactinol and raffinose in the leaves compared with wild-type plants under control growth conditions. High intracellular levels of galactinol and raffinose in the transgenic plants were correlated with increased tolerance to MV treatment and salinity or chilling stress. Galactinol and raffinose effectively protected salicylate from attack by hydroxyl radicals in vitro. These findings suggest the possibility that galactinol and raffinose scavenge hydroxyl radicals as a novel function to protect plant cells from oxidative damage caused by MV treatment, salinity, or chilling.

Highlights

Galactinol synthase (GolS) is a key enzyme in the synthesis of raffinose family oligosaccharides that function as osmoprotectants in plant cells
We reported that expression of GolS1 and GolS2 is under the control of heat shock transcription factor A2 (HsfA2) in Arabidopsis plants (Nishizawa et al, 2006)
The transcription of GolS1, -2, and -4 and raffinose synthase 2 (RS2) was highly induced in leaves of the Ox-HsfA2-6 plants compared with those of the wildtype plants under control growth conditions (25°C, 100 mE m22 s21; Fig. 2)

Summary

Introduction

Galactinol synthase (GolS) is a key enzyme in the synthesis of raffinose family oligosaccharides that function as osmoprotectants in plant cells. In leaves of Arabidopsis (Arabidopsis thaliana) plants overexpressing heat shock transcription factor A2 (HsfA2), the transcription of GolS1, -2, and -4 and raffinose synthase 2 (RS2) was highly induced; levels of galactinol and raffinose increased compared with those in wild-type plants under control growth conditions. GolS1or GolS2-overexpressing Arabidopsis plants (Ox-GolS1-11, Ox-GolS2-8, and Ox-GolS2-29) had increased levels of galactinol and raffinose in the leaves compared with wild-type plants under control growth conditions. High intracellular levels of galactinol and raffinose in the transgenic plants were correlated with increased tolerance to MV treatment and salinity or chilling stress. It is generally accepted that the imposition of environmental stress, such as drought, chilling, heat, and high-light irradiation, gives rise to excess concentrations of reactive oxygen species (ROS) and that much of the injury to plants caused by exposure to stress is associated with oxidative damage at the cellular level (Bowler et al, 1992; Foyer et al, 1994; Alscher et al, 1997; Shigeoka et al, 2002)

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