CHARACTERIZATION OF THE SEX-INDUCER GLYCOPROTEIN OF VOLVOX-CARTERI F WEISMANNIA

Sexual inducer pheromones from Volvox carteri f. weismannia, strains 65-30(12) and 1B were purified and characterized as glycoproteins with apparent molecular weights of 27 kDa and 28.5 kDa, respectively. This subspecies yielded 20-40 times more pheromone based on weight per spheroid than Volvox carteri f. nagariensis, but its specific activity (threshold dilution) is four to five orders of magnitude less (10(-12) to 10(-13) M). Gas-chromatographic sugar analysis revealed quantitative differences in the composition of the O- and N-glucans compared with the V. carteri f. nagariensis inducer. The V. carteri f. weismannia pheromones showed antigenic cross-reaction with an antiserum directed against chemically deglycosylated inducer from V. carteri f. nagariensis. However, there is only unilateral biological cross-induction. The V. carteri f. nagariensis inducer is strictly competent for its own gonidia only; the inducers from V. carteri f. weismannia also cross-induce V. carteri f. nagariensis. This pattern of cross-induction suggests the existence of related pheromone receptors but with different ligand specificities.