Characterization and expression analysis of wall-associated kinase (WAK) and WAK-like family in cotton.

The wall-associated kinases (WAKs) and WAK-like kinases (WAKLs) form a group of receptor-like kinases (RLKs) with extracellular domains tightly linked to the cell wall. The WAKs/WAKLs have been known to be involved in plant growth, development, and stress responses. However, the functions of WAKs/WAKLs are less well known in cotton. In this study, 58, 66, and 99 WAK / WAKL genes were identified in Gossypium arboreum , G. raimondii , and G. hirsutum , respectively. Phylogenetic analysis showed they were classified into five groups, with two groups specific to cotton. Collinearity analysis revealed that segmental and tandem duplications resulted in expansion of the WAK/WAKL gene family in cotton. Moreover, the Ka/Ks ratios indicated this family was exposed to purifying selection pressure during evolution. The structures of the GhWAK / WAKL genes and encoded proteins suggested the functions of WAKs/WAKLs in cotton were conserved. Transient expression of four WAK/WAKL-GFP fusion constructs in Arabidopsis protoplasts indicated that they were localized on the plasma membrane. The cis -elements in the GhWAK / WAKL promoters were responsive to multiple phytohormones and abiotic stresses. Expression profiling showed that GhWAK / WAKL genes were induced by various abiotic stresses. This study provides insights into the evolution of WAK / WAKL genes and presents fundamental information for further analysis in cotton. [ABSTRACT FROM AUTHOR]