THE SEX-INDUCING PHEROMONE AND WOUNDING TRIGGER THE SAME SET OF GENESIN THE MULTICELLULAR GREEN-ALGA VOLVOX

The sex-inducing pheromone of the multicellular green alga Volvox cart eri is a glycoprotein that triggers development of males and females a t a concentration <10(-16) M. By differential screening of a cDNA libr ary, two novel genes were identified that are transcribed under the co ntrol of this pheromone. Unexpectedly, one gene product was characteri zed as a lysozyme/chitinase, and the other gene product was shown to e ncode a polypeptide with a striking modular composition. This polypept ide has a cysteine protease domain separated by an extensin-like modul e from three repeats of a chitin binding domain. In higher plants, sim ilar protein families are known to play an important role in defense a gainst fungi. Indeed, we found that the same set of genes triggered by the sexual pheromone was also inducible in V. carteri by wounding.