GhNAC029 reduces cotton drought tolerance by negatively regulating NCED1-mediated ABA synthesis

Cotton (Gossypium hirsutism) is an important economic crop, accounting for 39% of natural fiber production. NAC transcription factors represent one of the largest transcription factor families and play an important role in plant responses to drought stress. However, most studies have been conducted in model plants such as Arabidopsis thaliana, while the regulatory mechanism in cotton require further investigation. Previous studies on genes associated with drought tolerance have predominantly focused on positive regulatory genes, with relatively few reports addressing negative regulatory genes. In this study, we analyzed the transcriptome differences between the drought-sensitive genotype XLZ8 (S) and the drought-tolerant genotype G95079 (G) at various time points during drought stress, identifying the key NAC transcription factor that negatively regulate the cotton drought tolerance gene GhNAC029 (Gh_A03G0887). Through virus-induced gene silencing (VIGS) and the transgenic lines, we demonstrated that GhNAC029 negatively regulated the cotton drought tolerance. Further investigation of GhNAC029 downstream regulated genes by transcription and CUT&Tag, we found GhNCED1, a crucial gene involved in abscisic acid (ABA) synthesis, which was down-regulated by GhNAC029. Additionally, exogenous ABA spraying, GhNAC029 was found to increase ABA sensitivity and reduce ABA biosynthesis. Therefore, we infer that GhNAC029 inhibits the expression of GhNCED1, leading to a decrease in ABA biosynthesis in cotton, which consequently weakens the cotton drought tolerance.