Identification and characterization of the ZmHSP20 genes in response to high temperature in maize

Abstract

Abstract High temperature is an emerging threat to maize productivity due to global warming. The HSP20 gene family has been reported to promote resistance to various abiotic stresses, but whether it is involved in high temperature response in maize is rarely known. Here, we identified 33 HSP20 genes (HSP20s) in maize via a conserved α-crystalline domain (ACD) scanning. The HSP20s can be divided into 14 subfamilies by the phylogenetic analysis. These genes distribute in all chromosomes and ten gene pairs may occur within duplication events. Fourteen members were predicted to have heat stress elements in their promoters, while seven of them locate in previously reported heat-resistance QTL (hrQTL) regions, accounting for 87.5% of the total hrQTL-related ZmHSP20s. Divergent tissue-specific expression profiles of ZmHSP20s were observed under normal conditions. Fourteen ZmHSP20s were co-upregulated in V4 and V5 leaves after high temperature treatment, while seven ZmHSP20s were stimulated concurrently in the kernel at daytime and nighttime high temperatures. These genes also show co-expression interactions with some ZmHSFs that are key factors in the heat-resistance pathway. The dynamic responses of candidate ZmHSP20s were further confirmed by real-time RT-PCR. Our study paves the way for further studies on the roles of ZmHSP20s in heat stress resistance.