Abstract
srd2 is a temperature-sensitive mutant of Arabidopsis thaliana that is defective in dedifferentiation and neo-meristem formation. Based on the phenotype of srd2, we consider that the competence for cell proliferation of hypocotyls is lower than that of roots and that SRD2-depended elevation of the competence is required in hypocotyls for the resumption of cell division but not in roots. The predicted product of SRD2 shares sequence similarity with human SNAP50, a subunit of SNAPc (snRNA activating protein complex). The level of snRNA increased in hypocotyls during dedifferentiation, and this increase was inhibited by the srd2 mutation. The results of transient assays of U2 snRNA promoter::LUC expression in cultured explants indicated that the srd2 mutation affects directly snRNA transcription. Moreover, the amount of snRNA in roots was found to be higher than that in hypocotyls. These findings suggest that the snRNA level limits the competence for cell proliferation.
