Maize Class C Heat Shock Factor ZmHSF21 Improves the High Temperature Tolerance of Transgenic Arabidopsis

High temperatures seriously threaten the global yield of maize. The objectives of the present study were to explore the key candidate gene involved in heat shock responses in maize and its potential biological function to heat stress. Here, we identified a Class C heat shock factor, ZmHSF21 , from maize leaves and used molecular biological and plant physiological assays to investigate its roles in transgenic Arabidopsis . ZmHSF21 encodes a putative protein of 388 amino acids. We showed that ZmHSF21 was expressed in most tissues of maize with relatively high expression in leaves and silks but rather low in roots and stalks, and its expression level in leaves was significantly up-regulated by heat treatment. We also showed that overexpression of ZmHSF21 in Arabidopsis significantly improved the seed germination frequency and plant survival rate when exposed to heat stress. We demonstrated that, compared with wild-type plants, the activities of peroxidase, superoxide dismutase, and catalase increased while the reactive oxygen species accumulation decreased in ZmHSF21 overexpressors under heat stress conditions. We further demonstrated that ZmHSF21 promoted the transcriptional level of AtAPX2 , AtGolS1, and several AtHSPs . Collectively, the first-class C HSF in maize ( ZmHSF21 ) is cloned in this study, and the combined results suggest that ZmHSF21 is a positive regulator of heat shock response and can be applied to develop maize high-temperature-tolerant varieties for more yield.