Family 1 GT, designated as UGT, is the largest and most functionally important multigene family in the plant kingdom. In this study, we carried out a genome-wide identification, analysis, and comparison of 142, 146, and 196 putative UGTs from Gossypium raimondii, Gossypium arboreum, and Gossypium hirsutum, respectively. All members present the 44 amino-acid conserved consensus sequence termed the plant secondary product glycosyltransferase motif. According to the phylogenetic relationship among the cotton UGT proteins and those from other species, GrUGTs and GaUGTs could be classified into 16 major phylogenetic groups (A-P), whereas GhUGTs are classified into 15 major phylogenetic groups with a lack of group C. All cotton UGTs are dispersed throughout the chromosomes and are displayed in clusters with the same open reading frame orientation. The expansion of them appears to result from genome duplication and rearrangement. Two conserved introns, A and B, are detected in most of the intron-containing-UGTs in G. raimondii and G. arboreum, whereas only intron A is detected in the intron-containing-UGTs in G. hirsutum. Furthermore, expression patterns of the UGT genes in G. hirsutum wild type and its near isogenic fuzzless-lintless mutant at the stage of fiber initiation were analyzed using the RNA-seq data. Overall, this study not only deepens our understanding of the structure, phylogeny, evolution, and expression of cotton UGT genes, but also provides a solid foundation for further cloning and functional studies of the UGT family genes.

Dominant glandless gene Gl 2 (e) was fine-mapped to a 15 kb region containing one candidate gene encoding an MYC transcription factor, sequence and expression level of the gene were analyzed. Cottonseed product is an excellent source of oil and protein. However, this nutrition source is greatly limited in utilization by the toxic gossypol in pigment glands. It is reported that the Gl 2 (e) gene could effectively inhibit the formation of the pigment glands. Here, three F2 populations were constructed using two pairs of near isogenic lines (NILs), which differ nearly only by the gland trait, for fine mapping of Gl 2 (e) . DNA markers were identified from recently developed cotton genome sequence. The Gl 2 (e) gene was located within a 15-kb genomic interval between two markers CS2 and CS4 on chromosome 12. Only one gene was identified in the genomic interval as the candidate for Gl 2 (e) which encodes a family member of MYC transcription factor with 475-amino acids. Unexpectedly, the results of expression analysis indicated that the MYC gene expresses in glanded lines while almost does not express in glandless lines. These results suggest that the MYC gene probably serves as a vital positive regulator in the organogenesis pathway of pigment gland, and low expression of this gene will not launch the downstream pathway of pigment gland formation. This is the first pigment gland-related gene identification in cotton and will facilitate the research on glandless trait, cotton MYC proteins and low-gossypol cotton breeding.