Comprehensive identification of potentially functional genes for transposon mobility in the C. elegans genome

Transposons are mobile DNA elements that encode genes for their own mobility. Whereas transposon copies accumulate on the genome during evolution, many lose their mobile activity due to mutations. Here, we focus on transposon-encoded genes that are directly involved in the replication, excision, and integration of transposon DNA, which we refer to as "transposon-mobility genes", in the Caenorhabditis elegans genome. Among the 62,773 copies of retro- and DNA transposons in the latest assembly of the C. elegans genome (VC2010), we found that the complete open reading frame structure was conserved in 290 transposon-mobility genes. Critical amino acids at the catalytic core were conserved in only 145 of these 290 genes. Thus, in contrast to the huge number of transposon copies in the genome, only a limited number of transposons are autonomously mobile. We conclude that the comprehensive identification of potentially functional transposon-mobility genes in all transposon orders of a single species can provide a basis of molecular analysis for revealing the developmental, aging, and evolutionary roles of transposons.