Abstract
Heat shock transcription factors (HSFs) play critical roles in several types of environmental stresses. However, the detailed regulatory mechanisms in response to salt stress are still largely unknown. In this study, we examined the salt-induced transcriptional responses of ThHSFA1-ThWRKY4 in Tamarix hispida and their functions and regulatory mechanisms in salt tolerance. ThHSFA1 protein acts as an upstream regulator that can directly activate ThWRKY4 expression by binding to the heat shock element (HSE) of the ThWRKY4 promoter using yeast one-hybrid (Y1H), chromatin immunoprecipitation (ChIP), and dual-luciferase reporter assays. ThHSFA1 and ThWRKY4 expression was significantly induced by salt stress and abscisic acid (ABA) treatment in the roots and leaves of T. hispida. ThHSFA1 is a nuclear-localized protein with transactivation activity at the C-terminus. Compared to nontransgenic plants, transgenic plants overexpressing ThHSFA1 displayed enhanced salt tolerance and exhibited reduced reactive oxygen species (ROS) levels and increased antioxidant enzyme activity levels under salt stress. Therefore, we further concluded that ThHSFA1 mediated the regulation of ThWRKY4 in response to salt stress in T. hispida.
Highlights
Salinity and secondary soil salinization have become serious ecological environmental problems worldwide, affecting plant growth and production by causing osmotic imbalance, mineral deficiency, and overall toxicity [1]
Similar to many other transcription factors (TFs), Heat shock transcription factors (HSFs) contain a conserved N-terminal DNA-binding domain (DBD), which can bind to cis-acting heat shock element (HSE) recognition sequences in their target gene promoters [14]
We found that the positive yeast clone harboring an HSF gene grew better than the other yeast clones
Summary
Salinity and secondary soil salinization have become serious ecological environmental problems worldwide, affecting plant growth and production by causing osmotic imbalance, mineral deficiency, and overall toxicity [1]. The salt and drought tolerance of AtHsfA6a-overexpressing plants is enhanced via the abscisic acid (ABA) signaling pathway, and these plants exhibit increased expression of downstream stress-responsive genes [10]. In addition to the roles of these HSFs in herbaceous plants, Populus euphratica PeHSF overexpression in tobacco maintains leaf ROS homeostasis and enhances antioxidant enzyme activity levels under salt stress conditions [4]. Transgenic plants overexpressing cotton GhWRKY6-like gene or sweet potato IbWRKY2 display enhanced salt tolerance by regulating the ABA signaling pathway and ROS scavenging [30,32]. The expression of FtWRKY46 from buckwheat, DgWRKY4 and DgWRKY5 from chrysanthemum, and GarWRKY5 from cotton in transgenic plants was shown to confer enhanced tolerance to salt stress by modulating ROS clearance, antioxidant enzyme activity, and stress-related gene expression [6,33,34,35]. ThHSFA1 and ThWRKY4 are involved in the same physiological and molecular regulatory pathways of the salt stress response
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