Comprehensive molecular evolutionary analysis of small heat shock proteins in five diploid Gossypium species

The small heat shock proteins (sHSPs) are important components in plant growth and development, and stress response. However, a systematical understanding of the sHSP family is yet to be reported in five diploid Gossypium species. In this study, 34 GlsHSPs, 36 GrsHSPs, 37 GtsHSPs, 37 GasHSPs, and 38 GhesHSPs were identified in Gossypium longicalyx, Gossypium raimondii, Gossypium turneri, Gossypium arboreum, and Gossypium herbaceum, respectively. These sHSP members can be clustered into 10 subfamilies. Different subfamilies had different member numbers, motif distributions, gene structures, gene duplication events, gene loss numbers, and cis-regulatory elements. Besides, the paleohexaploidization event in cotton ancestor led to expanding the sHSP members and it was also inherited by five diploid Gossypium species. After the cotton ancestor divergence, the sHSP members had the relatively conserved evolution in five diploid Gossypium species. The comprehensive evolutionary history of the sHSP family was revealed in five diploid Gossypium species. Furthermore, several GasHSPs and GhesHSPs were important candidates in plant growth and development, and stress response. These current findings can provide valuable information for the molecular evolution and further functional research of the sHSP family in cotton.