GhPAS1, a bHLH transcription factor in upland cotton (Gossypium hirsutum), positively regulates Verticillium dahlia resistance

Upland cotton (Gossypium hirsutum) is an important cash crop producing both fiber and oilseed, the yield and quality of which are severely affected by Verticillium wilt primarily caused by Verticillium dahliae infection. In this study, a cotton root expressed gene, GhPAS1, that encodes a basic helix-loop-helix (bHLH) transcription factor (TF), was significantly induced by Verticillium dahliae in cotton variety ZM24. Further investigation suggested that GhPAS1 may play a pivotal role in Verticillium wilt resistance in cotton, whereby the genetic attenuation of GhPAS1 resulted in a raised susceptibility to Verticillium dahliae; and conversely, overexpression of GhPAS1 in ZM24 significantly ameliorated the infection symptoms. RNA-seq analysis revealed that the expression of numerous ethylene-responsive factors (ERFs) genes and genes involved in lignin biosynthesis and plant defense were upregulated in cotton plants overexpressing GhPAS1 in response to Verticillium dahlia infection. Moreover, using dual-luciferase assay and electrophoretic mobility shift assay, GhPAS1 was shown to specifically enhance the promoter activities of GhERF5, GhERF14, GhPER42, GhPER64, and GhRPS5, among which GhERF14 and GhPER64, are directly related to Verticillium wilt resistance. Overall, these findings demonstrate that GhPAS1 plays a vital role in conferring Verticillium wilt resistance by regulating specific members of ERFs, as well as the genes involved in lignin biosynthesis and plant defense, providing new insights into the underlying mechanism of Verticillium wilt resistance and devising novel breeding and biotechnological strategies to enhance disease resistance in cotton.