Interspecies distribution of abundant DNA sequences inLilium

Summary The most abundantly repeated sequences in the very large genomes ofLilium henryi andLilium longiflorum have been characterized. DNA reannealed by a Cot of 1 Ms, which specifies the half reannealing point of sequences repeated 18–19,000 times per genome, was used to probe genomic libraries and restriction digests of each species. InL. henryi this fraction includes 2.2% of the genome, wheareas 9.7% of theL. longiflorum genome reanneals by Cot 1. The most abundant repeat identified was thedel retrotransposon. This is at least three times more common in the genome ofL. longiflorum than inL. henryi where it occurs in excess of 13,000 copies. It was also detected in the genomes of 12 otherLilium species examined. None of these have more copies ofdel per genome thanL. longiflorum, some having at least 100-fold fewer. The phylogenetic distribution ofdel across the genus suggests repeated, sporadic amplification events. Another very abundant repeat was identified as 5S ribosomal DNA (rDNA). In this case many more copies were present in the genome ofL. henryi than inL. longiflorum. The number of 5S rDNA copies also varied markedly across other members of the genus with a distribution unrelated todel.