The Rop (Rho-related protein from plants) subfamily plays a role in diverse cellular processes, including cytoskeletal organization, pollen and vegetative cell growth, hormone responses, stress responses, and pathogen resistance. Rops are able to regulate several downstream pathways to amplify a specific signal by acting as master switches early in the signaling cascade. They transmit a variety of extracellular and intracellular signals. Rops are involved in establishing cell polarity in root-hair development, root-hair elongation, pollen-tube growth, cell-shape formation, responses to hormones such as abscisic acid (ABA) and auxin, responses to abiotic stresses such as oxygen deprivation, and disease resistance and disease susceptibility. An individual Rop can have a unique function or an overlapping function shared with other Rop proteins; in addition, a given Rop-regulated function can be controlled by one or multiple Rop proteins. For example, Rop1, Rop3, and Rop5 are all involved in pollen-tube growth; Rop2 plays a role in response to low-oxygen environments, cell-morphology, and root-hair development; root-hair development is also regulated by Rop4 and Rop6; Rop6 is also responsible for ABA response, and ABA response is also regulated by Rop10. Plants retain some of the regulatory mechanisms that are shared by other members of the Rho family, but have also developed a number of unique modes for regulating Rops. Unique RhoGEFs have been identified that are exclusively active toward Rop proteins, such as those containing the domain PRONE (plant-specific Rop nucleotide exchanger). Most Rho proteins contain a lipid modification site at the C-terminus, with a typical sequence motif CaaX, where a = an aliphatic amino acid and X = any amino acid. Lipid binding is essential for membrane attachment, a key feature of most Rho proteins. Due to the presence of truncated sequences in this CD, the lipid modification site is not available for annotation.