Repeat sequence interspersion in coding DNA of peas does not reflect that in total pea DNA

Abstract

The pattern of sequence organization in the regions of the pea genome near sequences coding for mRNA differs significantly from that in total DNA. Interspersion of repeated and single copy sequences is so extensive that 85% of 1300 nucleotide-long fragments contain highly repetitive sequences (about 5000 copies per haploid genome). However, data presented here demonstrate that sequences which code for mRNA are enriched in the small fraction of fragments which do not contain these highly repetitive sequences. Thus, in contrast to the great majority of other sequences in the genome, most mRNA coding sequences are not located within 1300 nucleotides of highly repetitive elements. Moreover, our data indicate that those repeats (if any) which are closely associated with mRNA coding sequences belong to low copy number families characterized by an unusually low degree of sequence divergence.

Vicilin genes ofPisum

“…From these data we conclude that dispersed repeated DNA sequences are sometimes found in close proximity to sequences homologous to mRNAs in the pea genome. This is in contrast to the suggestion of Murray and Thompson (1982) that most mRNA coding sequences are not located within 1300 nucleotides of highly repetitive elements.…”

Insertional Polymorphism and Antiquity ofPDR1Retrotransposon Insertions in Pisum Species

“…Thirty-nine percent of the identifiable target sequences for PDR1 insertion are themselves transposable elements and a further 31% are unknown repetitive sequences, which are likely to be mainly composed of unidentified mobile elements or their relics. This is unsurprising, because Pisum has a large genome (4.5 3 10 9 bp haploid) and like other similarly sized plant genomes, including the quite closely related Vicia genus (Hill et al 2005), is known to be composed predominantly of repetitive DNA (Murray and Thompson 1982). RBIP markers derived from such insertions into repeated sequences should have yielded unoccupied-site PCR products in most or all pea samples but, interestingly, this did not happen in most cases (data not shown).…”

An integrated and comparative view of pea genetic and cytogenetic maps

“…50% of 5me C are in the sequence C(A/T)G (Pradhan & Adams, 1995). The pea genome is composed mainly of high copy dispersed repeated sequences, and thermal denaturation studies have shown these to be distinct sequence classes (Murray & Thompson, 1982). Taxonomically, pea is within the Vicieae family of the legumes, and is thus closely related to Vicia and Lathyrus .…”