Identification of cell-type specific alternative transcripts in the multicellular alga Volvox carteri.

Background: Cell type specialization is a hallmark of complex multicellular organisms and is usually established through implementation of cell-type-specific gene expression programs. The multicellular green alga Volvox carteri has just two cell types, germ and soma, that have previously been shown to have very different transcriptome compositions which match their specialized roles. Here we interrogated another potential mechanism for differentiation in V.

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

Volvocine algae constitute a unique comparative model for investigating the evolution of oogamy from isogamous mating types. The sex- or mating type-determining gene encodes a conserved RWP-RK transcription factor found in either the or male mating locus of dioecious volvocine species. We previously found that from the isogamous species () could not induce ectopic spermatogenesis when expressed heterologously in females, suggesting coevolution of Mid function with gamete dimorphism.

Genetics: swinging ciliates' seven sexes.

Ciliates are well known for their unusual tricks of nuclear remodeling. A roulette-like method for mating type choice in Tetrahymena adds an interesting new twist to their repertoire.

Evolution of sex and mating loci: an expanded view from Volvocine algae.

Sexual reproduction in Volvocine algae coevolved with the acquisition of multicellularity. Unicellular genera such as Chlamydomonas and small colonial genera from this group have classical mating types with equal-sized gametes, while larger multicellular genera such as Volvox have differentiated males and females that produce sperm and eggs respectively. Newly available sequence from the Volvox and Chlamydomonas genomes and mating loci open up the potential to investigate how sex-determining regions co-evolve with major changes in development and sexual reproduction.