Expression of rice heat stress transcription factor OsHsfA2e enhances tolerance to environmental stresses in transgenic Arabidopsis

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Abstract
Plant growth and crop yields are limited by high-temperature stresses. In this study, we attempted to isolate the rice genes responsible for high-temperature stress tolerance using a transformed Arabidopsis population expressing a full-length cDNA library of rice. From approximately 20,000 lines of transgenic Arabidopsis, we isolated a thermotolerant line, R04333, that could survive transient heat stress at the cotyledon stage. The rice cDNA inserted in R04333 encodes OsHsfA2e, a member of the heat stress transcription factors. The thermotolerant phenotype was observed in newly constructed transgenic Arabidopsis plants expressing OsHsfA2e. Among 5 A2-type HSF genes encoded in the rice genome, four genes, including OsHsfA2e, are induced by high temperatures in rice seedlings. The OsHsfA2e protein was localized to the nuclear region and exhibited transcription activation activity in the C-terminal region. Microarray analysis demonstrated that under unstressed conditions transgenic Arabidopsis overexpressing OsHsfA2e highly expressed certain stress-associated genes, including several classes of heat-shock proteins. The thermotolerant phenotype was observed not only in the cotyledons but also in rosette leaves, inflorescence stems and seeds. In addition, transgenic Arabidopsis exhibited tolerance to high-salinity stress. These observations suggest that the OsHsfA2e may be useful in molecular breeding designed to improve the environmental stress tolerance of crops.