Operon Conservation and the Evolution of trans-Splicing in the Phylum Nematoda
Figure 1
The Evolution of Operons and SL Usage through the Phylum Nematoda
Operons and SL usage in trans-splicing have been mapped onto a phylogeny of the Nematoda illustrating the relationships of the nematodes studied based on analysis of the small subunit rRNA (adapted from [37,38]). Conserved operons have been identified in Rhabditina, Tylenchina, and Spriurina (clades V, IV, and III of [37]). While SL1 may be a synapomorphy for the phylum, SL2-like SLs are apparently restricted to the Rhabditina, as is their use in trans-splicing to downstream genes in operons. An independent radiation of SL1-like SLs is used for downstream gene trans-splicing in the Tylenchina, while the Spirurina use canonical SL1.