Analysis of rrd1, rrd2, and rid4, Temperature-sensitive Mutants of Arabidopsis That Form Fasciated Roots under the Restrictive Temperature.

Abstract

rrd1, rrd2, and rid4 are temperature-sensitive mutants of Arabidopsis that were isolated by screening with adventitious root formation as an index phenotype and characterized by forming fasciated roots at the restrictive temperature. Temperature-shift experiments with a semi-synchronized lateral rooting system showed that lateral root primordia of these mutants develop into fasciated roots when exposed to the restrictive temperature at the initial stage. Detailed observation of arising primordia indicated that expansion of the area where cell division is reactivated to form a root primordium results in the fasciation phenotype.
The rrd2 mutation was mapped within about 140 kb at the 54-cM position of chromosome I. Sequence analysis of this region of the rrd2 genome detected a single base substitution in a gene encoding a pentatricopeptide protein, which is presumed to cause the fasciation phenotype. This is very suggestive in consideration of our previous finding that RID4 encodes another pentatricopeptide protein.