A newly identified chemotactic sexual pheromone from Closterium ehrenbergii

In sexual reproduction of Closterium ehrenbergii, pairing with the sexual partner cells is the first process observed. A cell migration-inducing activity, specific for mating-type plus (mt(+); NIES-228) cells, was detected in the culture medium of mating-type minus (mt(-); NIES-229) cells. Light was necessary for Introduction of the active substance by mt(-) cells and for migration of mt(+) cells. The active substance was hear-labile and had an apparent molecular mass of 20 kDa, as determined by gel filtration. A protein of 20 kDa was detected in the active fraction of gel filtration after sodium dodecyl sulfate polyacrylamide gel electrophoresis. Based on these results, it is proposed that a chemotactic sexual pheromone involved in the formation of sexual pairs of cells is secreted by mt(-) cells of C. ehrenbergii and is proteinaceous, like other sexual pheromones secreted by Closterium species.