Abstract
We have developed a novel activation tagging system for Arabidopsis in which expression of tagged genes is specifically activated in postembryonic roots. Using this system, several mutants with altered room meristem patterns have been isolated. Two of the mutants, designated urp4 and urp5, were characterized by enhanced cell divisions in roots and their causal genes were found to encode homologous proteins with transcription factor motifs. While loss-of-function mutants of these genes did not show obvious abnormality, mutants of another member in the same family lost functional meristem in primary roots. Observation of their embryogenesis and marker analysis revealed that the mutants are defective in cell proliferation and formation of organ primordia for both roots and cotyledons. In yeast amino-terminal region of the protein was shown to activate gene transcription. Taken together these results suggest that this novel transcription factor-like protein acts in embryonic pattern formation and axis formation.
