ISOLATION OF Y-CHROMOSOME-SPECIFIC SEQUENCES FROM SILENE LATIFOLIA AND MAPPING OF MALE SEX-DETERMINING GENES USING REPRESENTATIONAL DIFFERENCE ANALYSIS

The genomic subtraction method representational difference analysis (R DA) was used to identify male-specific restriction fragments in the di oecious plant Silene latifolia. Male-specific restriction fragments ar e linked to the male sex chromosome (the Y chromosome). Four RDA-deriv ed male-specific restriction fragments were used to identify polymorph isms in a collection of X-ray generated mutant plants with either herm aphroditic or asexual flowers. Some of the mutants have cytologically detectable deletions in the Y chromosome that were correlated with los s of male-specific restriction fragments. One RDA-derived probe detect ed a restriction fragment present in all mutants, indicating that each has retained Y chromosomal DNA. The other three probes detected genom ic fragments that were linked in a region deleted in some hermaphrodit ic and some asexual mutants. Based on the mutant phenotypes and the co rrelation of cytologically visible deletions with loss of male-specifi c restriction fragments, these markers were assigned to positions on t he Y chromosome close to the carpel suppression locus. This RDA mappin g also revealed a Y-linked locus, not previously described, which is r esponsible for early stamen development.