Evolutionary divergence of the sex-determining gene MID uncoupled from the transition to anisogamy in volvocine algae

Sa Geng, Ayano Miyagi, James G. Umen

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10 Scopus citations

Abstract

Volvocine algae constitute a unique comparative model for investigating the evolution of oogamy from isogamous mating types. The sex- or mating type-determining gene MID encodes a conserved RWP-RK transcription factor found in either the MT− or male mating locus of dioecious volvocine species. We previously found that MID from the isogamous species Chlamydomonas reinhardtii (CrMID) could not induce ectopic spermatogenesis when expressed heterologously in Volvox carteri females, suggesting coevolution of Mid function with gamete dimorphism. Here we found that ectopic expression of MID from the anisogamous species Pleodorina starrii (PsMID) could efficiently induce spermatogenesis when expressed in V. carteri females and, unexpectedly, that GpMID from the isogamous species Gonium pectoralewas also able to induce V. carteri spermatogenesis. Neither VcMID nor GpMID could complement a C. reinhardtii mid mutant, at least partly owing to instability of heterologous Mid proteins. Our data show that Mid divergence was not a major contributor to the transition between isogamy and anisogamy/oogamy in volvocine algae, and instead implicate changes in cis-regulatory interactions and/or transacting factors of the Mid network in the evolution of sexual dimorphism.

Original languageEnglish
Article numberdev162537
JournalDevelopment (Cambridge)
Volume145
Issue number7
DOIs
StatePublished - Apr 2018

Keywords

  • Chlamydomonas
  • Gonium
  • Pleodorina
  • RWP-RK
  • Sex determination
  • Volvox

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