Genome-Wide Identification and Expression Analysis of RLCK-VII Subfamily Genes Reveal Their Roles in Stress Responses of Upland Cotton

Receptor-like cytoplasmic kinase VII (RLCK-VII) subfamily members are vital players in plant innate immunity and are also involved in plant development and abiotic stress tolerance. As a widely cultivated textile crop, upland cotton (<i>Gossypium hirsutum</i>) attaches great importance to the cotton industry worldwide. To obtain details of the composition, phylogeny, and putative function of RLCK-VII genes in upland cotton, genome-wide identification, evolutionary event analysis, and expression pattern examination of RLCK-VII subfamily genes in <i>G. hirsutum</i> were performed. There are 129 RLCK-VII members in upland cotton (<i>GhRLCKs</i>) and they were divided into nine groups based on their phylogenetic relationships. The gene structure and sequence features are relatively conserved within each group, which were divided based on their phylogenetic relationships, and consistent with those in <i>Arabidopsis</i>. The phylogenetic analysis results showed that RLCK-VII subfamily genes evolved in plants before the speciation of <i>Arabidopsis</i> and cotton, and segmental duplication was the major factor that caused the expansion of <i>GhRLCKs.</i> The diverse expression patterns of <i>GhRLCKs</i> in response to abiotic stresses (temperature, salt, and drought) and <i>V. dahliae</i> infection were observed. The candidates that may be involved in cotton’s response to these stresses are highlighted. <i>GhRLCK7</i> (<i>GhRLCK7A</i> and <i>D</i>), which is notably induced by <i>V. dahliae</i> infection, was demonstrated to positively regulate cotton defense against <i>V. dahliae</i> by the loss-of-function assay in cotton. These findings shed light on the details of the RLCK-VII subfamily in cotton and provide a scaffold for the further function elucidation and application of <i>GhRLCKs</i> for the germplasm innovation of cotton.