Evolution of an Expanded Sex-Determining Locus in Volvox

Abstract

Revealing Volvox: Female and male gametes of the green alga, Volvox , significantly differ in size. Those of Chlamydomonas , another green algae from a lineage that separated from Volvox some 200 million years ago, are the same size. We know sex in Chlamydomonas is governed by a sex-determining locus called MT . In a detailed comparison of the MT loci of Volvox and Chlamydomonas , Ferris et al. (p. 351 ) found that although MT has retained some similarity in gene order, its composition has greatly changed between the two species. In Volvox , new genes have been coopted into this locus and show sex-specific expression.