Abstract
We have reported that Arabidopsis transcription factors DREB1s regulate expression of abiotic stress-responsive genes. Rice has 10 DREB1 family genes, OsDREB1s. Overexpression of OsDREB1A in rice activated expression of target stress-responsive genes such as lip9 and improved stress tolerance to drought, high-salinity and cold. Recently, we reported that OsDREB1G had the highest transactivation activity among 10 OsDREB1s and OsDREB1F activated the GUS reporter gene driven by an rd29A promoter, but did not activate the gene driven by the lip9 promoter.
In this study, we analyzed DNA binding specificities of OsDREB1s by gelshift assays. 9 OsDREB1 proteins bound a DRE in the rd29A promoter. However, binding of OsDREB1F to a DRE in the lip9 promoter was very weak. We analyzed downstream genes of OsDREB1G using transgenic rice harboring OsDREB1G under control of a promoter responsive to dexamethasone (DEX-OsDREB1G plants). More than 200 genes were up-regulated in the transgenic rice. Northern analysis confirmed that many downstream genes were induced by DEX in both DEX-OsDREB1G and DEX-OsDREB1A plants commonly and at least two genes were induced specifically in the DEX-OsDREB1G plants.
