Functional Characterization of a Sugar Beet Transcription Factor in Salt Stress Tolerance.

The basic/helix-loop-helix (bHLH) transcription factor (TF) plays an important role for plant growth, development, and stress responses. Previously, proteomics of NaCl treated sugar beet leaves revealed that a bHLH TF, , was significantly increased under salt stress. The BvbHLH93 protein localized in the nucleus and exhibited activation activity. The expression of was significantly up-regulated in roots and leaves by salt stress, and the highest expression level in roots and leaves was 24 and 48 h after salt stress, respectively. Furthermore, constitutive expression of conferred enhanced salt tolerance in as indicated by longer roots and higher content of chlorophyll than wild type. Additionally, the ectopic expression lines accumulated less Na and MDA, but more K than the WT. Overexpression of the enhanced the activities of antioxidant enzymes by positively regulating the expression of antioxidant genes and . Compared to WT, the overexpression plants also had low expression levels of and , which are involved in reactive oxygen species (ROS) production. These results suggest that plays a key role in enhancing salt stress tolerance by enhancing antioxidant enzymes and decreasing ROS generation.