A comparative study of the structure of the rDNA intergenic spacer of Lens culinaris Medik., and other legume species.

As part of a project on lentil molecular genetics, the sequence of the 18S-25S ribosomal RNA gene intergenic spacer (IGS) of Lens culinaris Medik. was determined. DNA was cloned after polymerase chain reaction (PCR) amplification. The spacer of 2939 bp was composed of nonrepetitive sequences and four tandem arrays of repeated sequences, named A to D. C and D arrays were formed by the repetition of very short consensus sequences. Similarity was found between lentil and other legume species, in particular those of the Vicieae tribe. A transcription initiation site, putative sites of termination and processing, and promoter-enhancer sequences were detected by computer-aided searches. These sites resemble motifs conserved in the IGS sequences of other plant species. The conservation of motifs in the otherwise highly variable plant IGS sequences points to the relevance of these motifs as functional sequences.