Abstract
An arabidopsis mutant, rrd4, which was originally isolated as being temperature sensitive for root redifferentiation, is characterized by cytokinin-dependent defects of dedifferentiation at the restrictive temperature. This suggests that the RRD4 gene functions in sequestrating negative effects of cytokinin on dedifferentiation. Chromosome mapping located the RRD4 in the 64-kbp region at the 23-cM position of chromosome I. Sequence analysis of CDSs in this region identified an amber mutation in F20D23.23 of the mutant genome. Among T2 plants derived from the transgenic rrd4 mutant, into which a wild-type genome fragment containing F20D23.23 had been introduced, the presence of the introduced DNA and the ability of callus formation at the restrictive temperature were co-segregated. These results have led to the conclusion that the RRD4 gene corresponds to F20D23.23. The primary structure indicates that this gene encodes a protein similar to a murine tuftelin-interacting protein, TIP39.
