Genome analysis and replication behavior of a set of repetitive sequences of Lilium longiflorum

Abstract

The four clones, pLZH47, pLZ112, pLZ113, and pLZ122, previously assumed to contain DNA sequences that replicate during zygotene (zygDNA), actually had their replication behavior tested using a replication assay. Genome analysis was also done for each clone. All of the clones seem to be members of families of dispersed repetitive DNA. The number of copies per 2C genome are as follows: pLZH47, 13 500; pLZ112, >100; pLZ113, 200; and pLZ122, 3500. The replication assays measured the amount of hybridizable sequences available at the stage of leptotene (before zygotene DNA replication occurs) and at the stage of pachytene (after zygotene replication occurs). True zygDNA clones should have twice as many sequences to hybridize to at pachytene as at leptotene. None of the clones had the expected increase. One clone, pLZ122, did show a statistically significant increase (10%). It may consist of a mixture of zygDNA and non-zygDNA sequences. Alternatively, only 10% of the pLZ122 family members may function as zygDNA.Key words: meiosis, zygDNA sequences, synapsis, chromosome homology, genome structure.