Molecular Characterization Of Two ABA Insensitive 5 Orthologues In Brassica Rapa

ABA is one of the most important hormones in plant growth and development and the response to different kinds of abiotic stress.The bZIP transcription factor ABI5 has been demonstrated to be a critical factor in plant ABA response.However,the biological significance of ABI5 ortholog in Brassica rapa remain elusive.In the present study,we determined the biological role of BraABI5 a and BraABI5 b in plant ABA response,which are two ABI5 orthologs in Brassica rapa.We obtained following results:(1)The genome of Brassica rapa encoded two putative ABI5 orthologs,designated as BraABI5 a and BraABI5 b respectively.Both the gene and protein architecture of BraABI5 a and BraABI5 b are highly similar to ABI5.Phylogenetic analysis also revealed that BraABI5 a and BraABI5 b are highly similar to ABI5.(2)Gene expression pattern revealed that both BraABI5 a and BraABI5 b are significantly induced by ABA.Moreover,the express of BraABI5 b is also induced by drought or high salt.While,the express of BraABI5 a isn't significantly induced by drought or high salt.(3)Subcellular localization showed that both BraABI5 a and BraABI5 b are mainly distributed in the nucleus of cell.(4)Yeast-one-hybrid based transactivation assay displayed that both BraABI5 a and BraABI5 b have transactivation activity,both of which are able to activate the expression of HIS reporter gene driven by hexamers of ABRE.(5)The ABA insensitive phenotype of Arabidopsis abi5-1 is completely suppressed in transgenic lines expressing BraABI5 a or BraABI5 b.Overall,these results suggest that ABI5 orthologs,BraABI5 a and Bra ABI5 b,have key roles in ABA response in Brassica rapa.