INTERSPECIES DISTRIBUTION OF ABUNDANT DNA-SEQUENCES IN LILIUM

The most abundantly repeated sequences in the very large genomes of Lilium henryi and Lilium 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. In L. henryi this fraction includes 2.2% of the genome, wheareas 9.7% of the L. longiflorum genome reanneals by Cot 1. The most abundant repeat identified was the del retrotransposon. This is at least three times more common in the genome of L. longiflorum than in L. henryi where it occurs in excess of 13,000 copies. It was also detected in the genomes of 12 other Lilium species examined. None of these have more copies of del per genome than L. longiflorum, some having at least 100-fold fewer. The phylogenetic distribution of del 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 of L. henryi than in L. longiflorum. The number of 5S rDNA copies also varied markedly across other members of the genus with a distribution unrelated to del. © 1990 Springer-Verlag New York Inc.