Physiological characterization of the sex pheromone protoplast‐release‐inducing protein from the Closterium peracerosum‐strigosum‐littorale complex (Charophyta)

Abstract

SUMMARYIn the unicellular charophycean alga Closterium peracerosum‐strigosum‐littorale complex, the protoplast‐release‐inducing protein (PR‐IP), a sex pheromone responsible for gametic protoplast release from mating‐type minus (mt–) cells, was found to stimulate secretion of mucilage from the cells. Induction of sexual cell division by PR‐IP was also confirmed. Bioassays were used to determine the minimum doses required to induce these functions, revealing that 5 · 10−16 M of PR‐IP stimulated mucilage secretion, and that 5 · 10−10 M of PR‐IP were required for protoplast release. Exposure of the cells to 5 · 10−11 M of PR‐IP resulted in the induction of sexual cell division as well as mucilage secretion. These results strongly suggest that PR‐IP is a multifunctional pheromone that independently promotes multiple steps in conjugation at the appropriate times through different induction mechanisms.