Evolutionary tree of lepidopteran and dipteran desaturase genes. Only genes from species for which complete sequences and biochemical activity have been reported were used in the tree construction, as well as predicted full-length sequences from dipteran genomes. The Neighbour-Joining tree was reconstructed using aa sequences and the JTT algorithm (MEGA 3.1, ); numbers along branches indicate bootstrap support from 1,500 replicates. The accession numbers for all sequences are given in connection with the abbreviated species name (and are listed in Fig. 3, in addition to Aae, Aedes aegypti; Aga, Anopheles gambiae; Ban, Belgica antartica; Cpi, Culex pipiens; Dme, Drosophila melanogaster; Dps, Drosophila pseudoobscura; Dsi, Drosophila simulans and Mdo, Musca domestica (Diptera) and Has, Helicoverpa assulta; Ofu, Ostrinia furnacalis, Mbr, Mamestra brassicae (Lepidoptera). The four desaturase-encoding cDNAs from this study are indicated by a triangle (Δ). Arrows indicate duplication events leading to lepidopteran-specific desaturase gene lineages. Biochemical activities are indicated in connection to the species name, NF refers to an non-functional transcript. The tree was rooted using the aa desaturase sequence from the tick Amblyomma americanum [10, 21, 30].