Proline-rich extensin-like receptor kinases (PERKs) are an important class of receptor kinases in plants. Receptor kinases comprise large gene families in many plant species, including the 15 PERK genes in Arabidopsis. At present, there is no comprehensive published study of PERK genes in G. hirsutum. Our study identified 33 PERK genes in G. hirsutum. Phylogenetic analysis of conserved PERK protein sequences from 15 plant species grouped them into four well defined clades. The GhPERK gene family is an evolutionarily advanced gene family that lost its introns over time. Several cis-elements were identified in the promoter regions of the GhPERK genes that are important in regulating growth, development, light responses and the response to several stresses. In addition, we found evidence for gene loss or addition through segmental or whole genome duplication in cotton. Gene duplication and synteny analysis identified 149 orthologous/paralogous gene pairs. Ka/Ks values show that most GhPERK genes experienced strong purifying selection during the rapid evolution of the gene family. GhPERK genes showed high expression levels in leaves and during ovule development. Furthermore, the expression of GhPERK genes can be regulated by abiotic stresses and phytohormone treatments. Additionally, PERK genes could be involved in several molecular, biological and physiological processes that might be the result of functional divergence.

Cotton is one of the major world oil crops. Cottonseed oil meets the increasing demand of fried food, ruminant feed, and renewable bio-fuels. MADS intervening keratin-like and C-terminal (MIKC)-type MADS-box genes encode transcription factors that have crucial roles in various plant developmental processes. Nevertheless, this gene family has not been characterized, nor its functions investigated, in cotton. Here, we performed a comprehensive analysis of MIKC-type MADS genes in the tetraploid Gossypium hirsutum L., which is the most widely cultivated cotton species. In total, 110 GhMIKC genes were identified and phylogenetically classified into 13 subfamilies. The Flowering locus C (FLC) subfamily was absent in the Gossypium hirsutum L. genome but is found in Arabidopsis and Vitis vinifera L. Among the genes, 108 were distributed across the 13 A and 12 of the D genome's chromosomes, while two were located in scaffolds. GhMIKCs within subfamilies displayed similar exon/intron characteristics and conserved motif compositions. According to RNA-sequencing, most MIKC genes exhibited high flowering-associated expression profiles. A quantitative real-time PCR analysis revealed that some crucial MIKC genes determined the identities of the five flower organs. Furthermore, the overexpression of GhAGL17.9 in Arabidopsis caused an early flowering phenotype. Meanwhile, the expression levels of the flowering-related genes CONSTANS (CO), LEAFY (LFY) and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1) were significantly increased in these lines. These results provide useful information for future studies of GhMIKCs' regulation of cotton flowering.

Background: RING-H2 finger E3 ligase (RH2FE3) genes encode cysteine-rich proteins that mediate E3 ubiquitin ligase activity and degrade target substrates. The roles of these genes in plant responses to phytohormones and abiotic stresses are well documented in various species, but their roles in cotton fiber development are poorly understood. To date, genome-wide identification and expression analyses of Gossypium hirsutum RH2FE3 genes have not been reported.