Flowering is a prerequisite for flowering plants to complete reproduction, and flowering time has an important effect on the high and stable yields of crops. However, there are limited reports on flowering-related genes at the genomic level in cotton. In this study, genomewide analysis of the evolutionary relationship of flowering-related genes in different cotton species shows that the numbers of flowering-related genes in the genomes of tetraploid cotton species Gossypium hirsutum and Gossypium barbadense were similar, and that these numbers were approximately twice as much as the number in diploid cotton species Gossypium arboretum. The classification of flowering-related genes shows that most of them belong to the photoperiod and circadian clock flowering pathway. The distribution of flowering-related genes on the chromosomes of the At and Dt subgenomes was similar, with no subgenomic preference detected. In addition, most of the flowering-related core genes in Arabidopsis thaliana had homologs in the cotton genome, but the copy numbers and expression patterns were disparate; moreover, flowering-related genes underwent purifying selection throughout the evolutionary and selection processes. Although the differentiation and reorganization of many key genes of the cotton flowering regulatory network occurred throughout the evolutionary and selection processes, most of them, especially those involved in the important flowering regulatory networks, have been relatively conserved and preferentially selected.
Keywords: evolution; expression analysis; flowering-related genes; genomewide; regulatory pathways; upland cotton.