Intragenic Complementation of Cellulose Synthase-Like D1 alleles in Root Hair Development

Root hair cells form the primary interface of plants with the soil environment, playing key roles in nutrient uptake and plant defense. In addition, they are typically the first cells infected by nitrogen-fixing soil bacteria during the root nodule symbiosis. Here we report a role for the Cellulose Synthase-Like D1 (CSLD1) gene in root hair development in Lotus japonicus. CSLD1 belongs to the cellulose synthase protein family that includes cellulose synthases, and cellulose synthase-like proteins, the latter thought to be involved in the biosynthesis of hemicellulose. We describe 11 csld1 mutant alleles that have either short (Ljcsld1-1) or variable length roots hairs (Ljcsld1-2 to 11). Examination of Ljcsld1-1 and one variable-length root hair mutant, Ljcsld1-6 showed increased root hair cell wall thickness, which in Ljcsld1-1 was more pronounced, suggesting a possible link with the defect in root nodule symbiosis. In addition, Ljcsld1-1 heterozygotes had intermediate root hair lengths, between those of wild type and the homozygotes. Intragenic complementation was observed between alleles with mutations in the N-terminal domain and other alleles, suggesting modularity of CSLD1 function and that it may operate as a homodimer or multimer. One sentence summaryThis research describes novel gain- and loss-of-function mutations at the Lotus japonicus CELLULOSE SYNTHASE-LIKE D1 locus and analyzes their impact on root hair development.