Transcription factor GbTCP20 confers plant wilt resistance by regulating ACC biosynthesis pathway and lignin deposition.

As a family of plant-specific transcription factors, the TEOSINTE BRANCHED 1, CYCLOIDEA, and PROLIFERATING CELL FACTOR (TCP) family plays a pivotal role in biotic stress responses. Verticillium dahliae, a devastating soil-borne fungal pathogen, causes severe vascular wilt in numerous crops. Several studies have reported that TCPs modulate defense signaling against various pathogens, while their molecular mechanisms in regulating the resistance to V. dahliae remain poorly characterized. In this study, we identified a TCP transcription factor in Gossypium barbadense acc. Hai7124, GbTCP20, that positively regulates V. dahliae resistance. The transcript level of GbTCP20 was significantly upregulated upon V. dahliae attack. Silencing GbTCP20 compromised the cotton resistance to V. dahliae, while overexpressing GbTCP20 in Arabidopsis significantly enhanced plant wilt resistance. Cis-acting element analysis of promoters from differentially expressed genes obtained by comparing root transcriptomes between GbTCP20-silenced and control plants, identified GbERF4 and GbCOMT as candidate downstream genes of GbTCP20, which GbERF4 encodes an AP2/ERF transcription factor involved in modulating 1-aminocyclopropane-1-carboxylic acid (ACC) biosynthesis pathway, and GbCOMT encodes caffeic acid O-methyltransferase, a pivotal enzyme in the lignin biosynthesis pathway. The Dual-Luciferase reporter assay confirmed that GbTCP20 enhances GbERF4 and GbCOMT expression via direct binding to their promoters. Overexpressing GbTCP20 in Arabidopsis elevated the expression of AtERF4, leading to increased AtACS2 and AtACS6 transcript level. Silencing GbTCP20 in G. barbadense acc. Hai7124 inhibited the expression of GbCOMT, leading to decreased lignin content in the stem. Our study reveals that GbTCP20 confers dual defense strategies against Verticillium wilt through both ACC-mediated chemical defense and lignin-based physical barriers in cotton.