Abstract
rrd1 was isolated by screening with callus-mediated root redifferentiation as an index phenotype and characterized by forming fasciated roots at the restrictive temperature. We performed temperature-shift experiments with a semi-synchronized lateral root formation system, which showed that lateral root primordia of rrd1 develop into fasciated roots when exposed to the restrictive temperature at the initial stage. From this result, the rrd1 mutant is inferred to have a temperature-dependent defect in the control of cell division to a limited area during root primordium initiation.
The rrd1 mutation was mapped within about 85 kb at the 40-cM position of chromosome III. Sequence analysis of this region of the rrd1 genome detected a single base substitution in At3g25430, a gene encoding a protein similar to poly(A)-specific ribonuclease (PARN). The mutation in At3g25430 is presumed to cause carboxy-terminal truncation of its protein product, which might be responsible for the rrd1 phenotype.
