GhGGB negatively regulates drought resistance in Gossypium hirsutum, potentially via prenylation-dependent suppression of ABA biosynthesis through GhROP1/8 modification

Protein prenylation, a key post-translational modification which can be mediated by geranylgeranyltransferases (GGTs), has been implicated in plant stress responses, but its role and mechanism in cotton remain elusive. Here, we demonstrate that the β-subunit of type I protein geranylgeranyltransferase in Gossypium hirsutum (GhGGB) negatively regulates drought resistance. Virus-induced gene silencing (VIGS) of GhGGB significantly enhanced drought survival rates by 40 % compared to controls, accompanied by improved physiological indices of drought tolerance. We identified two cotton Rho-related GTPases(ROP), GhROP1 and GhROP8, as interacting partners of GhGGB through Bimolecular Fluorescence Complementation (BiFC) and GST pull-down assays. The interaction affinity was determined by the C-terminal CaaL prenylation motif. Silencing GhROP1 or GhROP8 similarly enhanced drought tolerance, with enhanced survival rates of 30 % and 37 %, respectively. Mechanistically, silencing GhGGB, GhROP1, and GhROP8 altered the transcriptional landscape of hormonal pathways, characterized by the upregulation of key ABA biosynthesis and signaling genes alongside the downregulation of auxin-related biosynthetic and responsive genes. Our findings suggest that the GhGGB-GhROP1/8 module functions as a negative regulator of drought resistance, presumably through the prenylation of ROPs to coordinate the balance between ABA and auxin pathways at the transcriptional level. Taken together, this module presents a promising breeding strategy for developing high-yielding, drought-resilient cotton cultivars without growth penalties.