Systematic Characterization of TCP Gene Family in Four Cotton Species Revealed That GhTCP62 Regulates Branching in Arabidopsis

SIMPLE SUMMARY: TCP transcription factors (TF) are indispensable for the normal functioning of plant growth and development. This study identified and performed phylogenetic analysis on 218 TCP genes in four cotton species. We also observed conserved exon-intron structures and protein motif distribution patterns in GhTCP genes. GhTCP62 was enriched in the axillary bud, indicating that it plays a role in branching. GhTCP62 is a nuclear-localized TF, the overexpression of which decreases the number of cauline-leaf branches and rosette-leaf branches in Arabidopsis. Additionally, the expression levels of HB21 and HB40 genes increased in plants with GhTCP62 overexpression, demonstrating that GhTCP62 could regulate branching by regulating HB21 and HB40. Collectively, the GhTCP62 TF located in the nucleus was highly enriched in the axillary buds, and GhTCP62 overexpression lines demonstrated fewer rosette-leaf branches and cauline-leaf branches, indicating that GhTCP62 regulates branching in Arabidopsis. ABSTRACT: TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors play an essential role in regulating various physiological and biochemical functions during plant growth. However, the function of TCP transcription factors in G. hirsutum has not yet been studied. In this study, we performed genome-wide identification and correlation analysis of the TCP transcription factor family in G. hirsutum. We identified 72 non-redundant GhTCP genes and divided them into seven subfamilies, based on phylogenetic analysis. Most GhTCP genes in the same subfamily displayed similar exon and intron structures and featured highly conserved motif structures in their subfamily. Additionally, the pattern of chromosomal distribution demonstrated that GhTCP genes were unevenly distributed on 24 out of 26 chromosomes, and that fragment replication was the main replication event of GhTCP genes. In TB1 sub-family genes, GhTCP62 was highly expressed in the axillary buds, suggesting that GhTCP62 significantly affected cotton branching. Additionally, subcellular localization results indicated that GhTCP62 is located in the nucleus and possesses typical transcription factor characteristics. The overexpression of GhTCP62 in Arabidopsis resulted in fewer rosette-leaf branches and cauline-leaf branches. Furthermore, the increased expression of HB21 and HB40 genes in Arabidopsis plants overexpressing GhTCP62 suggests that GhTCP62 may regulate branching by positively regulating HB21 and HB40.