Arabidopsis DREB1A confers high salinity tolerance and regulates the expression of GA dioxygenases in Tobacco

Abstract

AtDREB1A driven by the CaMV 35S or the stress-inducible rd29A promoter were introduced into tobacco plants to investigate the role of AtDREB1A in salt stress. The AtDREB1A-expressing plants showed higher root length and chlorophyll content, and had elevated levels of soluble sugars under high salinity conditions compared to control plants. The expression of LEA ( NtERD10B and NtLEA5) and Suc- phosphate- synthase A ( NtSPSA, which encodes a key enzyme involved in sucrose biosynthesis) increased under salt stress in control plants. Moreover, their expression was up-regulated by AtDREB1A in transgenic plants under normal conditions and further enhanced by high salt, which at least partially contributed to the high salt tolerance in AtDREB1A-expressing plants. On the other hand, overexpression of AtDREB1A caused a dwarf phenotype. The expression of NtGA3ox and NtGA2ox increased while NtGA20ox seemed slightly decreased in AtDREB1A-overexpressing plants or under salt stress in wild-type tobacco plants. Exogenous GA 3 treatment did not restore the dwarf phenotype except for the enlarged leaf area and the lengthened petiole. These results suggest that overexpression of AtDREB1A confers salt tolerance and regulates the expression of GA dioxygenases in the similar way as salt stress in tobacco plants. The possible mechanism leading to the dwarf phenotype in AtDREB1A-overexpressing plants is discussed.