A bHLH transcription factor, SlbHLH96, promotes drought tolerance in tomato

Abstract

Drought stress caused by water deficit reduces plant productivity in many regions of the world. In plants, basic helix-loop-helix (bHLH) transcription factors regulate a wide range of cellular activities related to growth, development and stress response; however, the role of tomato SlbHLHs in drought stress responses remains elusive. Here, we used reverse genetics approaches to reveal the function of <i>SlbHLH96</i>, which is induced by drought and abscisic acid (ABA) treatment. We found that <i>SlbHLH96</i> functions as a positive regulator of drought tolerance in tomato. Overexpression of <i>SlbHLH96</i> in tomato improves drought tolerance by stimulating the expression of genes encoding antioxidants, ABA signaling molecules and stress-related proteins. In contrast, silencing of <i>SlbHLH96</i> in tomato reduces drought tolerance. SlbHLH96 physically interacts with an ethylene-responsive factor, SlERF4, and silencing of <i>SlERF4</i> in tomato also decreases drought tolerance. Furthermore, SlbHLH96 can repress the expression of the ABA catabolic gene, <i>SlCYP707A2</i>, through direct binding to its promoter. Our results uncover a novel mechanism of <i>SlbHLH96-</i>mediated drought tolerance in tomato plants, which can be exploited for breeding drought-resilient crops.