Abstract
Root hairs are tubular extensions from root epidermal cells and elongate by tip growth. It has been suggested that actin cytoskeleton plays an important role in the process of tip growth. However, little is understood about a direct role of actin cytoskeleton in root-hair development. We isolated a novel Arabidopsis missense mutation in the ACT2 gene encoding a member of actin expressed in vegetative tissues. In the heterozygote, root-hair growth was inhibited and aerial parts of the plant showed dwarf phenotype. In the homozygote, any root hairs were not formed and growth of the plant was disturbed severely to result in seedling lethal. Transgenic plant expressing a mutant-formed ACT2 protein showed the phenotypes of the mutant as described above, indicating that the mutant protein have dominant-negative effects to cause morphological defects. We will discuss possible roles of actin cytoskeleton in root-hair development and cell expansion.
