A pentamer-repeat-containing DNA sequence in Texas bluebonnet (Lupinus texensis Hook.)

A 654-bp EcoRI restriction fragment called Lup4 was shotgun cloned from Texas bluebonnet (Lupinus texensis Hook.) nuclear genomic DNA that had been extracted from plant leaves. Its sequence was determined on both strands. Southern blot analysis of EcoRI-digested Texas bluebonnet DNA revealed clone hybridization throughout the approximately 1.0 to > 23 kb size range; the darkest hybridization was in the high molecular weight range (approximately 6 to > 23 kb). Using dot blot analysis, the copy number of the 654-bp clone was estimated to be approximately 4.75 x 10(4) copies per haploid genome, and thus this repetitive sequence comprises 3.5-4.1% of the nuclear genome. Sequence analyses showed that this clone contains multiple repeats: mainly the ATTGG pentamer, but also derivative pentamers (e.g., GTTGG, TTTGG, ATAGG, and GGATT). Examination of DNA base occurrence revealed a strand bias in base composition. Data-base searches using the algorithm FASTA revealed no alignment with existing plant data base sequences, but showed sequence identity with several telomeric and satellite DNA sequences. The two highest-scoring alignments were with another pentamer-containing sequence from a telomeric region of the nematode Parascaris univalens.