Guo Huimin, Zhai Weibo, Zhang Shanshan, Guo Anhui, Zhang Wenwei, Jian Guiliang, Duan Jiangyan, Qi Fangjun
As an important and conserved cascade signaling pathway in eukaryotes, the mitogen-activated protein kinase (MAPK) signaling cascade is composed of three kinds of sequentially phosphorylated protein kinases, MAPKKK, MAPKK, and MAPK. MAPKs play an important role in a number of processes including the regulation of plant growth, stress responses, and disease resistance. To fully understand the genetic relationship between cotton MAPK, MAPKK, MAPKKK family members, and further reveal the functional roles of cotton MAPKs in stress responses and disease resistance, we collected amino acid sequences of MAPK, MAPKK, and MAPKKK family members in Gossypium hirsutum from the NCBI database, based on published data of the G. raimondii and G. arboreum genome; then performed homologous comparisons and phylogenetic analysis of family members from G. hirsutum, G. raimondii, and G. arboreum. The results showed that cotton MAPK family members contain Thr-Glu-Tyr (TEY) or Thr-Asp-Tyr (TDY) phosphorylation sites and can be divided into four subfamilies (group A, B, C, and D) according to their amino acid sequences. The TEY subtype can be classified into three groups, A, B, and C, whereas the TDY subtype contains only group D. Cotton MAPKK family members, which have a characteristic conservative S/T-X5-S/T area and the active site motif D(I/L/V)K, can also be divided into four subfamilies (group A, B, C and D) according to their amino acid sequences. Members of the cotton MAPKKK family fall into two main classes: MEK and Raf, with the former containing the conserved region G(T/S)PX(W/Y)MAPEV and the latter GTXX(W/Y)MAPE(L/V). Clarifying the relationships between cotton MAPK, MAPKK, and MAPKKK family members will help us to further to reveal the roles of cotton MAPKs in stress responses and disease resistance.