Crosstalk between Rho of Plants GTPase signalling and plant hormones.

This article focuses on the roles of Rho of Plants (ROPs), a plant-specific subgroup of small guanine nucleotide-binding proteins, in mediating crosstalk between cellular signalling and plant hormone pathways, particularly auxin and abscisic acid (ABA). ROPs regulate diverse cellular processes such as cell growth, morphogenesis, and organ development by acting as molecular switches that influence cytoskeleton dynamics and membrane trafficking. The review highlights how auxin rapidly activates ROPs via the ABP1/ABL1/2-TMK1 receptor complex to modulate PIN transporter localization and auxin distribution, while ABA generally inactivates ROPs to promote responses like stomatal closure, with ROPs interacting directly with ABA signalling components such as ABI1/2. Additionally, the article discusses emerging evidence of ROP interactions with other hormones including cytokinin, brassinosteroid, and salicylic acid, and emphasizes the challenges and future directions in elucidating ROP-hormone signalling integration at cellular and tissue levels in multicellular plants.