Pheromone-Inducible Glycoproteins of the Extracellular Matrix of Volvox and Their Possible Role in Sexual Induction

Members of the genus Volvox are simple, multicellular, eukaryotic organisms and each individual is composed of only two types of cells: Somatic and reproductive. Asexual and sexual development of Volvox carteri have been repeatedly described in detail (Starr 1969, 1970). Gamete formation is inducible by the action of a pheromone. In Volvox carteri the sexual pheromone was characterized as a 30 000 - Da glycoprotein (Starr et al. 1974 Gilles et al. 1981), which is synthesized and excreted by sperm cells. The biochemical mechanism of the pheromone’s action is almost completely unknown. The ultimate target of the pheromone’s action obviously is the gonidium, which responds with production of sexual rather than asexual offspring. However, all biochemical responses to the pheromone detected so far turned out to originate from somatic cells. In this paper we describe pheromone-induced synthesis of sulphated glycoproteins by somatic cells. In addition we discuss possible functions of these extracellular matrix components.