Glutaredoxins (Grxs) are ubiquitous small heat-stable disulfide oxidoreductases that play a crucial role in plant development and response to oxidative stress. Here, a novel cDNA fragment (SlGRX1) from tomato encoding a protein containing the consensus Grx family domain with a CGFS active site was isolated and characterized. Southern blot analysis indicated that SlGRX1 gene had a single copy in tomato genome. Quantitative real-time RT-PCR analysis revealed that SlGRX1 was expressed ubiquitously in tomato including leaf, root, stem and flower, and its expression could be induced by oxidative, drought, and salt stresses. Virus-induced gene silencing mediated silencing of SlGRX1 in tomato led to increased sensitivity to oxidative and salt stresses with decreased relative chlorophyll content, and reduced tolerance to drought stress with decreased relative water content. In contrast, over-expression of SlGRX1 in Arabidopsis plants significantly increased resistance of plants to oxidative, drought, and salt stresses. Furthermore, expression levels of oxidative, drought and salt stress related genes Apx2, Apx6, and RD22 were up-regulated in SlGRX1-overexpressed Arabidopsis plants when analyzed by quantitative real-time PCR. Our results suggest that the Grx gene SlGRX1 plays an important role in regulating abiotic tolerance against oxidative, drought, and salt stresses.

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