Nat Commun. 2018 Aug 10;9(1):3216. doi:10.1038/s41467-018-05712-5

Kanzaki N, Tsai IJ, Tanaka R, Hunt VL, Liu D, Tsuyama K, Maeda Y, Namai S, Kumagai R, Tracey A, Holroyd N, Doyle SR, Woodruff GC, Murase K, Kitazume H, Chai C, Akagi A, Panda O, Ke HM, Schroeder FC, Wang J, Berriman M, Sternberg PW, Sugimoto A, Kikuchi T.

Biology and genome of a newly discovered sibling species of Caenorhabditis elegans

123-Mb genome assembled into six chromosomes. Divergence time between C. elegans and C. inopinata estimated to about 10.5 Mya (142.73 million generations ago, assuming a generation time of 30 days). Proliferation of transposons and other repetitive elements (LTR, LINE, and Tc1/mariner). “The C. inopinata genome contains 641 LTR retrotransposon elements, 104 of which contain full protein domains (intact LTRs) In comparison, C. elegans and C. briggsae have 62 and 128 LTR retrotransposon elements, respectively, with 10 intact LTRs found in each.” “The most common type of repetitive sequence in the C. inopinata genome is the TcMar transposase Tc1 family [...] comprising 8.85% of the genome, compared with 1.31% and 3.04% of the C. elegans and C. briggsae genomes, respectively”. “Gene collinearity is largely conserved despite frequent intra chromosomal rearrangements.” “Higher synonymous substitution rates (dS) in autosomal arm regions than in the centre regions for C. elegans and C. inopinata one-to-one orthologues.” “Notably, C. inopinata has highly conserved gene synteny and orthology of essential genes with C. elegans and C. briggsae, but differs substantially in morphology and ecology. We hypothesise that activation of transposable elements possibly due to de-silencing through an altered small RNA pathway could be a driving force of rapid diversification of C. inopinata from other Caenorhabditis species.”