Identification of the STY13 gene family across the entire genome and an analysis of the essential function of GhSTY13-12 in cotton's response to abiotic stress.

Cotton is an important cash crop, and its yield and quality were affected by abiotic stresses. The serine/threonine protein kinase STY13 gene, belonging to the protein kinase family, is one of the largest and most functionally diverse gene families, which is a critical regulatory molecule for cell function. In this study, we systematically identified and analyzed the STY13 gene family in two major cultivated cotton species (Gossypium hirsutum and Gossypium barbadense) and their two ancestors (Gossypium arboretum and Gossypium raimondii). A total of 46, 50, 26 and 24 STY13 genes were identified from these four species, respectively. Phylogeny analysis showed that cotton STY13 genes (cotton STY protein kinase genes) could be classified into five groups. This gene family was evenly distributed on each chromosome in cotton. STY13 genes contain light-responsive elements, stress-responsive elements, growth and developmental elements, and multiple gene and protein binding sites. Most motifs in the STY13 proteins were conserved and had similar distribution patterns. However, there were some differences in specific motifs in different subfamilies. Gene expression analysis based on RNA-seq and qRT-PCR showed that STY13 genes were responsive to abiotic stress. GhSTY13-12 gene was located in cytoplasm. Silencing of the GhSTY13-12 gene resulted in reduced leaf chlorosis, increased total antioxidant capacity, decreased malondialdehyde content, and enhanced drought and salt tolerance. These results provide a scientific basis for further research on the function of STY13 in cotton and its application on cotton trait improvement.