Genome-wide characterization of the UDP-glycosyltransferase gene family reveals their potential roles in leaf senescence in cotton

Uridine diphosphate (UDP) glycosyltransferases (UGTs) involved in many metabolic processes and are essential for plant growth and development. Although UGTs proteins have been studied in many plants, the biological functions of UGT genes in cotton leaf senescence are still unknown. In the present study, we performed a genome-wide survey and identified 157 GrUGT, 152 GaUGT and 261 GHUGT genes in Gossypium raimondii, G. arboreum, and G. hirsutum, respectively, that were classified into 15 groups. Analysis of protein motif and gene structure demonstrated that structural and functional conservation occurred within same groups but diverged among the different groups. Gene duplication analysis indicated the different duplication ways happened between tetraploid G. hirsutum and the two diploid species. Whole genome or segmental duplications played a main role in the expansion of the GHUGT family in cotton, and experienced purifying selection during the long evolutionary process in cotton. Cis-acting regulatory elements analysis indicated that they were associated with complex hormone regulatory networks and the stress response. Additionally, to identify GHUGT candidate genes responsive to leaf senescence, we analyzed the expression patterns of GHUGT genes using our transcriptome data from two cultivars of upland cotton with contrasting tolerance to leaf senescence. Subsequently, gene expression profiling based on real-time quantitative PCR showed that selected GHUGT candidate genes might be involved in ABA and JA regulation. Through further functional verification, silencing GHUGT116 gene via VIGS (Virus-induced gene silencing) delayed dark-induced leaf senescence. Overall, the results provide useful and valuable information for understanding the evolution of cotton UGTs genes and the function in leaf senescence.