Isolation of BAC clones containing conserved genes from libraries of three distantly related moths: a useful resource for comparative genomics of Lepidoptera

Abstract

Lepidoptera, butterflies and moths, is the second largest animal order and includes numerous agricultural pests. To facilitate comparative genomics in Lepidoptera, we isolated BAC clones containing conserved and putative single-copy genes from libraries of three pests, Heliothis virescens, Ostrinia nubilalis, and Plutella xylostella, harboring the haploid chromosome number, n = 31, which are not closely related with each other or with the silkworm, Bombyx mori, (n = 28), the sequenced model lepidopteran. A total of 108-184 clones representing 101-182 conserved genes were isolated for each species. For 79 genes, clones were isolated from more than two species, which will be useful as common markers for analysis using fluorescence in situ hybridization (FISH), as well as for comparison of genome sequence among multiple species. The PCR-based clone isolation method presented here is applicable to species which lack a sequenced genome but have a significant collection of cDNA or EST sequences.

Figure 1

Schematic representation of phylogeny of Lepidoptera and haploid chromosome numbers of species referred to in the text. The phylogeny is based on the studies of Regier et al. [18]. Neither Bombycoidea nor Noctuidae are monophyletic, but form a clade clearly distinguishable from Pyraloidea and butterflies including Papilionoidea [18].

Figure 2

Strategy for selection of genes and ESTs in this experiment. Known genes and ESTs [13, 16, 25] were used as queries against a B. mori genome database, Kaikobase [20]. ESTs published later [14, 15, 17] were searched when no candidates were found in the first selection.

Figure 3

Venn diagram showing the total number of genes used for BAC isolation and those corresponding among the three species.