REGULATORY SYSTEMS OF ROOT PATTERNING

Genetic regulatory system of root patterning is being studied using Ar abidopsis mutants, One mutant, hy5, shows ''expanded root pattern'', T he cloned HY5 gene encodes a bZIP transcription factor. Transgenic Ara bidopsis plants overexpressing HY5 show reduced formation and elongati on of lateral roots, suggesting that HY5 works as a negative regulator of lateral root formation and elongation, Another mutant with fewer r oot hairs, caprice, has a mutation in a gene encoding a protein with a Myb-like DNA binding domain typical of transcription factors. Genetic and transgenic analyses have revealed that the CAPRICE gene works as a positive regulator for the epidermal cell differentiation to become root-hair-forming cells, by repressing the negative regulator, GL2. We are also studying a mechanism on the switching mechanism determining growth of normal root hairs (agar type) or growth of stimulus-induced hairs (air type).