Overexpression of the alfalfa DnaJ-like protein (MsDJLP) gene enhances tolerance to chilling and heat stresses in transgenic tobacco plants

Abstract

Heat shock proteins (HSPs) are generally considered as important molecular chaperones; they are known to perform criticalfunctions in plant development and abiotic stress response processes. In this study, we examined the role of a HSP, the Medicagosativa DnaJ-like protein (MsDJLP), in alfalfa and its potential application for the development of abiotic stress tolerance in plants. Wefound that expression of the MsDJLP gene was induced by chilling (4 °C) and heat (42 °C), but not by cadmium (500 µM) or arsenic(500 µM) stresses. We then cloned the MsDJLP gene downstream of the strong constitutive CaMV 35S promoter and transformedit into tobacco plants. Ectopic expression of MsDJLP conferred enhanced tolerance to both chilling and heat stresses in transgenictobacco plants. Under chilling stress, the transgenic tobacco plants showed lower $H_2O_2$ accumulation and electrolyte leakage (EL)activity, and better photosystem II efficiency than wild-type (WT) plants, indicating that photoinhibition was less severe in transgeniccompared to WT plants. Following heat treatment, the transgenic plants showed better relative chlorophyll and water contents, andlower malondialdehyde accumulation than WT plants. Our study provides evidence for a pivotal role of MsDJLP for chilling and heatstress tolerance in transgenic tobacco plants.