Abstract
We have previously described the Arabidopsis semi-dominant mutant uni-1D. UNI encodes a CC-NBS-LRR-type protein belonging to the R gene family. Its mutation results in constitutive PR-1 gene expression and interesting morphological phenotypes: heterozygotes display bushy, dwarf phenotypes, forming many narrow leaves and inducing many ectopic axillary meristems, whereas homozygotes die in the early stage of true leaf formation after germination. The molecular basis of how uni-1D can induce these phenotypes is unknown. In this study, we focused on a UNI-interacting protein, isolated by Y2H screening, which was identified as the RPT2a subunit of the 26S proteasome. The phenotype of an rpt2a single mutant displayed pleiotropic defects such as the formation of abnormally shaped leaves, disrupted phyllotaxy and retarded root growth. The effect of the uni-1D mutation on morphology, particularly on initial ectopic axillary meristem formation, was suppressed in this rpt2a mutant. Moreover, lethality of the uni-1D homozygote was also suppressed in rpt2aand its phenotype became heterozygote-like. These results suggest that the expression of uni-1D phenotypes may be mediated by RPT2a.
