A NEWLY IDENTIFIED CHEMOTACTIC SEXUAL PHEROMONE FROM CLOSTERIUM-EHRENBERGII

In sexual reproduction of Closterium ehrenbergii, pairing with the sex ual partner cells is the first process observed. A cell migration-indu cing activity, specific for mating-type plus (mt(+); NIES-228) cells, was detected in the culture medium of mating-type minus (mt(-); NIES-2 29) cells. Light was necessary for Introduction of the active substanc e by mt(-) cells and for migration of mt(+) cells. The active substanc e was hear-labile and had an apparent molecular mass of 20 kDa, as det ermined by gel filtration. A protein of 20 kDa was detected in the act ive fraction of gel filtration after sodium dodecyl sulfate polyacryla mide gel electrophoresis. Based on these results, it is proposed that a chemotactic sexual pheromone involved in the formation of sexual pai rs of cells is secreted by mt(-) cells of C. ehrenbergii and is protei naceous, like other sexual pheromones secreted by Closterium species.