carpel, a new Arabidopsis epi-mutant of the SUPERMAN gene: Phenotypic analysis and DNA methylation status

The carpel (car) mutation affects the morphology of reproductive organs in Arabidopsis thaliana, car flowers have an increased number of carpels, on a verage 2.7+/-0.8 instead of two in the wild type. Through allelism test wit h fon1-3 and analysis of the methylation state of the SUPERMAN (SUP) gene i n car mutants, we show that car is an epi-mutation of SUP. The methylation pattern of car is clearly distinct from that of fon1-3, another epimutation of the SUP gene. Methylation was found predominantly in Cp(A/T)p(A/G) trip lets and in CpG pairs. We suggest that the extensive SUP methylation in car has arisen from an abundant methylation of a single CpG site that was alre ady present in abscisic acid-insensitive (abi3-4) mutants, from which car w as segregating.