CHROMOSOMAL LOCALIZATION OF REPETITIVE SEQUENCES IN A DIOECIOUS PLANT, SILENE LATIFOLIA

We have studied a dioecious plant, Silene latifolia Poiret ssp. alba, also known as Melandrium album Garcke. Sex determination of S. latifolia, is strictly dependent on sex chromosomes. The female plant has two X chromosomes whereas the male plant has one X chromosome and one Y chromosome. Direct isolation of Y chromosome-DNA was performed by an automatic microdissection system with ultraviolet laserbeam. FISH analysis with amplified DNA from the dissected Y chromosome revealed that the Y chromosome did not have the Y chromosome-specific enriched sequences. A highly repetitive sequence, RMY1 was detected at both ends of the X chromosome and at one end near the pseudoautosomal region of the Y chromosome. Twelve fragments with interstitial telomeric repeats were isolated from a genomic DNA library using (CCCTAAA)_5 as an oligo probe. Eight of them were classified into four types. Genomic Southern hybridization using these fragments as probes showed the identical hybridized pattern between male and female genomes. Copia-like and gypsy-like retrotransposons were isolated by PCR with primers in reverse transcriptase domains. FISH analyses revealed that these retrotransposons distributed over all chromosomes. Pylogenetic analyses using copia-like retrotransposons of 14 different species in the genus Silene suggested that the dioecy in the section including S. latifolia, S. dioica and S. diclinis evolved recently.