Structural analysis of a Lotus japonicus genome. I. Sequence features and mapping of fifty-six TAC clones which cover the 5.4 mb regions of the genome.

A total of 56 TAC clones with an average insert size of 100 kb were isolated from a TAC library of the Lotus japonicus genome based on the expressed sequences tags (ESTs), cDNA and gene information, and their nucleotide sequences were determined according to the shot-gun based strategy. The total length of the sequenced regions is 5,473,195 bp. By comparison with the sequences in protein and EST databases and analysis with computer programs for gene modeling, a total of 605 potential protein-encoding genes with known or predicted functions, 69 gene segments, and 172 pseudogenes were identified. The average density of the genes assigned so far is 1 gene/8120 bp. Introns were identified in approximately 78% of the potential genes. There was an average of 3.8 introns per gene and the average length of the introns was 375 bp. DNA markers were generated based on the nucleotide sequences obtained, and each clone was mapped onto the linkage map using the F2 mapping population derived from a cross of L. japonicus Gifu B-129 and Miyakojima MG-20. The sequence data, gene information and mapping information are available through the World Wide Web at http://www.kazusa.or.jp/lotus/.