Abstract
We have isolated eight dominant mutants with abnormal root cell patterns using the GAL4/UAS activation tagging system. These mutants were collectively named UAS-tagged root patterning (urp). Two of them, urp4-1D and urp5-1D, showed enhanced cell division in lateral root cap and epidermis. Determination of the UAS insertion sites, followed by cosegregation and recapituration analyses, indicated that the mutant phenotype was caused by ectopic expression of homologous genes encoding plant-specific transcription factor-like proteins. The URP4 recapituration lines showed severer phenotype than that of original urp4-1D, giving rise to callus-like morphology. A callus-specific gene was found to be induced in these mutants and the URP4 promoter was active in callus. Furthermore, expressions of other homologous genes were also elevated in the URP4- and URP5-overexpressing plants. These observations suggest that URP4 and URP5 proteins function either in enhancing cell proliferation or in repressing cell differentiation.
