The plant-specific tau class of glutathione S-transferases (GSTs) is often highly stress-inducible and expressed in a tissue-specific manner, thereby suggesting its important protective roles. Although activities associated with the binding and transport of reactive metabolites have been proposed, little is known about the regulatory functions of GSTs. Expression of AtGSTU19 is induced by several stimuli, but the function of this GST remains unknown. In this study, we demonstrated that transgenic over-expressing (OE) plants showed enhanced tolerance to different abiotic stresses and increased percentage of seed germination and cotyledon emergence. Transgenic plants exhibited an increased level of proline and activities of antioxidant enzymes, along with decreased malonyldialdehyde level under stress conditions. Real-time polymerase chain reaction (PCR) analyses revealed that the expression levels of several stress-regulated genes were altered in AtGSTU19 OE plants. These results indicate that AtGSTU19 plays an important role in tolerance to salt/drought/methyl viologen stress in Arabidopsis.

Summary WRKY comprises a large family of transcription factors in plants, but most WRKY members are still poorly understood. In this study, we report the identification and functional characterization of PbrWRKY53 isolated from Pyrus betulaefolia . PbrWRKY53 was greatly up‐regulated by drought and abscisic acid, but slightly induced by salt and cold. Subcellar localization analyses showed that PbrWRKY53 was located in the nucleus. Ectopic expression of PbrWRKY53 in tobacco and Pyrus ussuriensis conferred enhanced tolerance to drought stress. The transgenic plants exhibited better water status, less reactive oxygen species generation and higher levels of antioxidant enzyme activities and metabolites than the wild type. In addition, overexpression of PbrWRKY53 in transgenic tobacco resulted in enhanced expression level of PbrNCED1 , and led to the increase in larger amount of vitamin C accumulation in comparison to WT. Knock‐down of PbrWRKY53 in P. ussuriensis down‐regulated PbrNCED1 abundance, accompanied by compromised drought tolerance. Yeast one‐hybrid assay, EMSA and transient expression analysis demonstrated that PbrWRKY53 could bind to the W‐box element in the promoter region of PbrNCED1 . Taken together, these results demonstrated that PbrWRKY53 plays a positive role in drought tolerance, which might be, at least in part, promoting production of vitamin C via regulating PbrNCED1 expression.

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In plants, anthocyanins often appear at specific developmental stages, but are also induced by a number of environmental factors. The coordinated expression of genes encoding the anthocyanin biosynthetic pathway enzymes is controlled at the transcriptional level usually by an R2R3Myb transcription factor. However, little is known about the effects of R2R3-Myb on plant resistance to environmental stresses. In this study, we introduced an R2R3Myb transcription factor gene Mdmyb10, a regulatory gene of anthocyanin biosynthesis in apple fruit, into Arabidopsis and analyzed its function to osmotic stress in transgenic plants. Under high osmotic stress, the Mdmyb10 over-expressing plants exhibited growth better than wild-type plants. The elevated tolerance of the transgenic plants to osmotic stress was confirmed by the changes of flavonoids, chlorophyll, malondialdehyde and proline contents. These results preliminarily showed that the Mdmyb10 can possibly be used to enhance the high osmotic-tolerant ability of plants.