MdbHLH130, an Apple bHLH Transcription Factor, Confers Water Stress Resistance by Regulating Stomatal Closure and ROS Homeostasis in Transgenic Tobacco

Abstract

Drought is a major environmental factor that significantly limits crop yield and quality worldwide. Basic helix-loop-helix (bHLH) transcription factors have been reported to participate in the regulation of various abiotic stresses. In this study, a bHLH transcription factor in apple, <i>MdbHLH130</i>, which contains a highly conserved bHLH domain, was isolated and characterized. qRT-PCR and <i>P_MdbHLH130::GUS</i> analyses showed that <i>MdbHLH130</i> was notably induced in response to dehydration stress. Compared with the wild-type (WT), transgenic apple calli overexpressing <i>MdbHLH130</i> displayed greater resistance to PEG6000 treatment. In contrast, the <i>MdbHLH130-Anti</i> lines were more sensitive to PEG6000 treatment than WT. Moreover, ectopic expression of <i>MdbHLH130</i> in tobacco improved tolerance to water deficit stress, and plants exhibited higher germination rates and survival rates, longer roots, and lower ABA-induced stomatal closure and leaf water loss than the WT control. Furthermore, overexpression of <i>MdbHLH130</i> in tobacco also led to lower electrolyte leakage, malondialdehyde contents, and reactive oxygen species (ROS) accumulation and upregulation of the expression of some ROS-scavenging and stress-responsive genes under water deficit stress. In addition, <i>MdbHLH130</i> transgenic tobacco plants exhibited improved tolerance to oxidative stress compared with WT. In conclusion, these results indicate that <i>MdbHLH130</i> acts as a positive regulator of water stress responses through modulating stomatal closure and ROS-scavenging in tobacco.