Fig. 3.

Gain of antisense introns in the highly conserved vps-4 locus. a Maximum-likelihood tree of vps-4 as retrieved by aligning the C. elegans vps-4 against 19 nematode genomes. The phylogeny of vps-4 orthologs is in agreement with the species tree, i.e. nematode species clades (I, III-V) appear in individual subtrees, indicating that the identified sequences represent one-to-one orthologs of vps-4. b Gene tree of npr-23. c genomic configuration of the vps-4 and npr-23 in 20 nematode genomes. This gene pair represents the only case of conservation across the complete nematode phylum. Nevertheless, this example shows that npr-23 has gained introns independently in clade III nematodes as well as in the Pristionchus lineage. Please note that vps-4 has three additional 5’exons in C. elegans which are not visible here as only conserved parts of the vps-4 gene structure are shown