Repetitive DNA and the Chromosomes in the Genome of Oil Palm (Elaeis guineensis)

Abstract

Like most plant genomes, much of the oil palm genome (Elaeis guineensis L., 2n=32) consists of repetitive DNA sequences. We aimed to isolate and characterize a range of repetitive sequences from the genome of the crop and analyse the repeats by sequencing, Southern and in situ hybridization. Three unrelated repetitive sequence families, with no homology to known sequences, showed a dispersed distribution along the chromosomes with concentration in the proximal parts of arms, while simple sequence repeats of DNA (GA, GATA and CAC) were clustered in the distal parts. Copia -like retroelements were dispersed throughout the genome, with a concentration in proximal regions, but were not as abundant as in species with larger genomes. Among tandemly repeated sequences, a major 18S-25S rDNA site was present on a single pair of chromosomal sites, often on a satellite with no visible connection to its parent chromosome. A major 5S rDNA site was located on another chromosome pair; variable numbers of minor sites of both rDNA families were also detected. The telomeric sequence (CCCTAAA) was located at the ends of all chromosome arms, but no intercalary sites of amplification were detected. No other major families of tandemly repeated sequences were found. The molecular cytogenetic analysis and chromosome amplification patterns of major sequence families provide the reference point for examination of genomic organization of major classes of the repetitive DNA in normal and in tissue culture material including abnormal regenerants.