JcDREB2, a Physic Nut AP2/ERF Gene, Alters Plant Growth and Salinity Stress Responses in Transgenic Rice

Abstract

Transcription factors of the AP2/ERF family play important roles in plant growth, development, and responses to biotic and abiotic stresses. In this study, a physic nut AP2/ERF gene, <i>JcDREB2</i>, was functionally characterized. Real-time PCR analysis revealed that <i>JcDREB2</i> was expressed mainly in the leaf and could be induced by abscisic acid but suppressed by gibberellin (GA) and salt. Transient expression of a JcDREB2-YFP fusion protein in Arabidopsis protoplasts cells suggested that JcDREB2 is localized in the nucleus. Rice plants overexpressing <i>JcDREB2</i> exhibited dwarf and GA-deficient phenotypes with shorter shoots and roots than those of wild-type plants. The dwarfism phenotype could be rescued by the application of exogenous GA₃. The expression levels of GA biosynthetic genes including <i>OsGA20ox1</i>, <i>OsGA20ox2</i>, <i>OsGA20ox4</i>, <i>OsGA3ox2, OsCPS1</i>, <i>OsKO2</i>, and <i>OsKAO</i> were significantly reduced in plants overexpressing <i>JcDREB2</i>. Overexpression of <i>JcDREB2</i> in rice increased sensitivity to salt stress. Increases in the expression levels of several salt-tolerance-related genes in response to salt stress were impaired in <i>JcDREB2</i>-overexpressing plants. These results demonstrated not only that <i>JcDREB2</i> influences GA metabolism, but also that it can participate in the regulation of the salt stress response in rice.