AtCSLD3, a cellulose synthase-like gene important for root hair growth in Arabidopsis

A member of the cellulose synthase-like (subfamily D) gene family of Arabid opsis, AtCSLD3, has been identified by T-DNA tagging. The analysis of the c orresponding mutant, csld3-1, showed that the AtCSLD3 gene plays a role in root hair growth in plants. Root: hairs grow in phases: First a bulge is fo rmed and then the root hair elongates by polarized growth, the so-called "t ip growth." In the mutant, root hairs were initiated at the correct positio n and grew into a bulge, but their elongation was severely reduced. The tip s of the csld3-1 root hairs easily leaked cytoplasm, indicating that the te nsile strength of the cell wall had changed at the site of the tip. Based o n the mutant phenotype and the functional conservation between CSLD3 and th e genuine cellulose synthase proteins, we hypothesized that the CSLD3 prote in is essential for the synthesis of polymers for the fast-growing primary cell wall at the root hair tip. The distinct mutant phenotype and the ubiqu itous expression pattern indicate that the CSLD3 gene product is only limit ing at the zone of the root hair tip, suggesting particular physical proper ties of the cell wall at this specific site of the root hair cell.