Turbellarian taxonomic database

Record # 23246

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Brand JN, Wiberg RAW, Pjeta R, Bertemes P, Beisel C, Ladurner P, Schärer L (2020)
RNA-Seq of three free-living flatworm species suggests rapid evolution of reproduction-related genes.
BMC Genomics Vol 21(1): 462
[doi: 10.1186/s12864-020-06862-x

Abstract / Notes

"Background The genus Macrostomum consists of small free-living flatworms and contains Macrostomum lignano,
which has been used in investigations of ageing, stem cell biology, bioadhesion, karyology, and sexual
selection in hermaphrodites. Two types of mating behaviour occur within this genus. Some species, includingM.
lignano, mate via reciprocal copulation, where, in a single mating, both partners insert their male copulatory
organ into the female storage organ and simultaneously donate and receive sperm. Other species mate via
hypodermic insemination, where worms use a needle-like copulatory organ to inject sperm into the tissue of the
partner. These contrasting mating behaviours are associated with striking differences in sperm and copulatory
organ morphology. Here we expand the genomic resources within the genus to representatives of both behaviour
types and investigate whether genes vary in their rate of evolution depending on their putative function.
Results We present de novo assembled transcriptomes of threeMacrostomumspecies, namely M. hystrix, a close
relative of M. lignanothat mates via hypodermic insemination,M. spirale, a more distantly related species that
mates via reciprocal copulation, and finally M. pusillum, which represents a clade that is only distantly
related to the other three species and also mates via hypodermic insemination. We infer 23,764 sets of
homologous genes and annotate them using experimental evidence fromM. lignano. Across the genus, we identify
521 gene families with conserved patterns of differential expression between juvenile vs. adult worms and 185
gene families with a putative expression in the testes that are restricted to the two reciprocally mating
species. Further, we show that homologs of putative reproduction-related genes have a higher protein
divergence across the four species than genes lacking such annotations and that they are more difficult to
identify across the four species, indicating that these genes evolve more rapidly, while genes involved in
neoblast function are more conserved. Conclusions This study improves the genusMacrostomumas a model system,
by providing resources for the targeted investigation of gene function in a broad range of species. And we,
for the first time, show that reproduction-related genes evolve at an accelerated rate in flatworms."

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