Abstract
For molecular genetics of plant organogenesis in vitro, we have isolated and characterized many temperature-sensitive mutants of Arabidopsis that are impaired in adventitious root formation. Here we report analysis of the process of cell proliferation reactivation with one of these mutant, rid2, whose responsible gene encodes a putative methyltransferase with a nuclear localization signal. Callus formation from hypocotyl explants of rid2 is highly temperature-sensitive. In hypocotyl explants, high temperature inhibited the re-initiation of cell cycle, and induced structural abnormality of nuclei accompanied with nucleolar enlargement and uneven cell expansion. By contrast, root explants of rid2 are partially temperature-sensitive for callus formation, and they show discontinuous callusing phenotype at high temperature. Closer observation revealed that in the non-callusing region, not cell cycle re-initiation but cell proliferation maintenance is interfered with. These results suggest that RID2 functions at two different points in the process of reactivation of cell proliferation.
