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Molecular coevolution of a sex pheromone and its receptor triggers reproductive isolation in Schizosaccharomyces pombe

  1. Chikashi Shimoda2
  1. Department of Biology, Graduate School of Science, Osaka City University, Osaka 558-8585, Japan

  1. Edited by Mitsuhiro Yanagida, Okinawa Institute of Science and Technology Graduate University, Onna-Son, Kunigami, Japan, and approved February 26, 2015 (received for review January 26, 2015)

Significance

Reproductive isolation is a key event leading to speciation as suggested by the observation of living populations in nature. This paper shows that novel reproductive populations of Schizosaccharomyces pombe, which are reproductively isolated from the WT population, can be created by genetically altering the primary structure of a mating pheromone and its receptor. Based on the biological concept of species, this reproductive group should be regarded as a new species. This is the first report, to our knowledge, of the artificial creation of a new species of any living organism in the history of evolutional research.

Abstract

The diversification of sex pheromones is regarded as one of the causes of prezygotic isolation that results in speciation. In the fission yeast Schizosaccharomyces pombe, the molecular recognition of a peptide pheromone by its receptor plays an essential role in sexual reproduction. We considered that molecular coevolution of a peptide-mating pheromone, M factor, and its receptor, Map3, might be realized by experimentally diversifying these proteins. Here, we report the successful creation of novel mating-type pairs by searching for map3 suppressor mutations that rescued the sterility of M-factor mutants that were previously isolated. Several strong suppressors were found to also recognize WT M factor. The substituted residues of these Map3 suppressors were mapped to F204, F214, and E249, which are likely to be critical residues for M-factor recognition. These critical residues were systematically substituted with each of the other amino acids by in vitro mutagenesis. Ultimately, we successfully obtained three novel mating-type pairs constituting reproductive groups. These novel mating-type pairs could not conjugate with WT maters. Furthermore, no flow of chromosomally integrated drug-resistance genes occurred between the novel and the WT mating pairs, showing that each experimentally created reproductive group [e.g., M factor(V5H) and Map3(F214H)] was isolated from the WT group. In conclusion, we have succeeded in creating an artificial reproductive group that is isolated from the WT group. In keeping with the biological concept of species, the artificial reproductive group is a new species.

Footnotes

  • ↵1Present address: Bioproduction Research Institute, National Institute of Advanced Industrial Science and Technology, Ibaraki 305-8566, Japan.

  • ↵2To whom correspondence should be addressed. Email: shimoda{at}sci.osaka-cu.ac.jp.

  • Author contributions: T.S., T.N., and C.S. designed research; T.S. and C.S. performed research; T.S. and C.S. analyzed data; and T.S. and C.S. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1501661112/-/DCSupplemental.

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