Volvox: Simple steps to developmental complexity?

Volvox, Chlamydomonas, and their close relatives – collectively the volvocine green algae – comprise an excellent system for investigating the origins of developmental complexity. Over a relatively short period of time Volvox evolved an impressive suite of developmental traits, including asymmetric cell division, multicellularity with germ-soma division of labor, embryonic morphogenesis, and oogamy. Recent molecular genetic analyses of important developmental genes and comparative analyses of the fully sequenced Volvox and Chlamydomonas genomes have provided important insights into how these and other traits came to be. Surprisingly, the acquisition of much of the developmental innovation in this family seems to have involved relatively minor tinkering with the ancestral unicellular blueprint.

Research highlights▶ Volvocine algae are now premier system for studying evolution of multicellularity. ▶ Cell differentiation probably evolved through rewiring of a stress–response pathway. ▶ Oogamy evolved through expansion/rapid evolution of sex genes. ▶ Volvox genome is very similar to that of its close unicellular cousin Chlamydomonas. ▶ Developmental complexity can evolve through relatively simple steps.