CLE25 peptide enhances drought tolerance in cotton (Gossypium hirsutum) by inducing abscisic acid biosynthesis

Drought is a leading abiotic factor affecting agricultural productivity. While AtCLE25 enhances drought tolerance by inducing abscisic acid (ABA) accumulation in Arabidopsis thaliana, the mechanisms by which GhCLE25 regulates drought tolerance in cotton (Gossypium hirsutum) remain unclear. In this study, the role of GhCLE25 in cotton drought tolerance was investigated using virus-induced gene silencing and exogenous CLE25 peptide treatment. GhCLE25 expression was significantly induced in both roots and leaves under natural and polyethylene glycol 6000 (PEG 6000)-simulated drought. Silencing GhCLE25 inhibited stomatal closure, increased water loss, and decreased drought tolerance, whereas exogenous CLE25 improved drought tolerance by inducing stomatal closure. Consistently, ABA content was decreased in GhCLE25-silenced plants but increased in CLE25-treated plants. Silencing GhCLE25 downregulated ABA biosynthetic genes (NCED2, NCED3, NCED5, and NCED9) but upregulated the ABA catabolic gene CYP707A1. Conversely, the expression of ABA biosynthetic and catabolic genes showed an opposite trend under CLE25 peptide treatment. Moreover, the ABA-responsive genes Late Embryogenesis Abundant (LEA) and RD29B were reduced in GhCLE25-silencing plants but increased following CLE25 treatment. Thus, these results suggest that GhCLE25 may regulate ABA levels by modulating the expression of ABA metabolism-related genes, which could further regulate stomatal closure and ABA-responsive gene expression to enhance drought tolerance in cotton.