The Sweetpotato BTB-TAZ Protein Gene,IbBT4, Enhances Drought Tolerance in TransgenicArabidopsis

BTB-TAZ (BT)-domain proteins regulate plant development and pathogen defense. However, their roles in resistance to abiotic stresses remain largely unknown. In this study, we found that the sweetpotato BT protein-encoding geneIbBT4significantly enhanced the drought tolerance ofArabidopsis.IbBT4expression was induced by PEG6000, H(2)O(2)and brassinosteroids (BRs). TheIbBT4-overexpressingArabidopsisseeds presented higher germination rates and longer roots in comparison with those of WT under 200 mM mannitol stress. Under drought stress the transgenicArabidopsisplants exhibited significantly increased survival rates and BR and proline contents and decreased water loss rates, MDA content and reactive oxygen species (ROS) levels.IbBT4overexpression upregulated the BR signaling pathway and proline biosynthesis genes and activated the ROS-scavenging system under drought stress. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays revealed that the IbBT4 protein interacts with BR-ENHANCED EXPRESSION 2 (BEE2). Taken together, these results indicate that theIbBT4gene provides drought tolerance by enhancing both the BR signaling pathway and proline biosynthesis and further activating the ROS-scavenging system in transgenicArabidopsis.