Rice RHC Encoding a Putative Cellulase is Essential for Normal Root Hair Elongation

Root hairs are tubular shaped protuberances of root epidermal cells and are found in nearly all vascular plants. Co-ordinate expression of a number of root hair morphogenesis genes involved in cytoskeleton reorganization, changes in homeostasis and distribution of ion gradients, and cell wall reassembly are required during root hair cell elongation. In this report, we have characterized a root hairspecific putative cellulase gene in rice, OsRHC. OsRHC is specifically expressed in elongating root hairs and OsRHC is targeted to the plasma membrane. The mutation of the OsRHC gene by a T-DNA knock-out and CRISPR-Cas9 system causes a severe reduction in root hair length. Bimolecular fluorescence complementation analysis demonstrated that the OsRHC protein interacts with a root hair-specific cellulose synthase protein (OsCSLD1) in the plasma membrane. Furthermore, we observed a moderate reduction of cellulose content in the osrhc mutant. Our results suggest that the plasma membrane-localized OsRHC plays a critical role in cell wall remodeling during root hair extension.