GhDREB1B-GhFAD3-2 module mediates drought tolerance by regulating linolenic acid biosynthesis in cotton.

Cotton (Gossypium hirsutum), serving as a critical raw material for textile manufacturing, is highly vulnerable to drought stress during its growth cycle. Water deficit conditions directly impair boll development and ultimately reduce lint yield. As a crucial unsaturated fatty acid, linolenic acid (C18:3) plays a pivotal role in plant growth and drought response. However, the specific role of C18:3 in drought tolerance and the underlying regulatory network remain largely unelucidated. In this study, drought treatment significantly reduced C18:3 content in cotton leaves, while exogenous application of C18:3 enhanced drought tolerance. Gene expression analysis indicated that the fatty acid desaturase GhFAD3-2 may be involved in the drought-induced reduction of C18:3 content. Overexpression of GhFAD3-2 improved drought tolerance in cotton, whereas silencing GhFAD3-2 decreased drought tolerance, potentially by regulating C18:3, jasmonic acid, and flavonoid metabolism. Further investigation revealed that GhDREB1B acted as an upstream transcriptional activator of GhFAD3-2, directly binding to the promoter of GhFAD3-2 to activate its transcription in response to drought stress in cotton. The expression of GhDREB1B was significantly suppressed under drought stress, and silencing GhDREB1B resulted in decreased GhFAD3-2 expression, reduced C18:3 content, and consequently diminished drought tolerance in cotton. In conclusion, this study elucidates the role of the GhDREB1B-GhFAD3-2 module in regulating C18:3 biosynthesis in response to drought stress in cotton, providing new insights into the molecular mechanisms of drought response and potential breeding targets for cotton.