A putative defensive function of trichocysts in Paramecium has been tested experimentally. Cells of trichocyst-non-discharge (tnd) mutant, artificially induced trichocyst-deficient cells, and intact wild-type cells were compared as prey for a carnivorous ciliate, Dileptus margaritifer. Cells of tnd mutants were eaten 9-45 times faster than wild-type cells by the predator in P. caudatum and P. tetraurelia. Encounters between paramecia and dilepti occurred in nearly the same frequency in mutant and wild-type cells. Paramecia with reduced numbers of trichocysts were obtained in P. caudatum, P. jenningsi, and P. tetraurelia by treating wild-type cells with lysozyme, a n inducer of trichocyst discharge. These cells were eaten faster than intact cells by the predator and the rate of predation was inversely correlated with the remained capacity of trichocyst discharge. It was concluded that the discharge of trichocysts defends these species of Paramecium against D. margaritifer. Therefore, the results of this work strongly support the hypothesis that trichocysts in Paramecium function as defensive organelles against predators. The results also support the hypothesis that the offense-defense interaction between Dileptus and Pramecium is mediated by their extrusomes (toxicysts and trichocysts) and suggest that extrusomes in ciliates function as organelles for interspecific cell-cell interaction.

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Conjugation in Blepharisma japonicum is induced by interaction between complementary mating-types I and II, which excrete blepharmone (gamone 1) and blepharismone (gamone 2), respectively. Gamone 1 transforms type II cells such that they can unite, and gamone 2 similarly transforms type I cells. Moreover, each gamone promotes the production of the other gamone. Gamone 2 has been identified as calcium-3-(2-formylamino-5-hydroxybenzoyl) lactate and has been synthesized chemically. Gamone 1 was isolated and characterized as a glycoprotein of 20 -30 kDa containing 175 amino acids and 6 sugars. However, the amino acid sequence and arrangement of sugars in this gamone are still unknown. To determine partial amino acid sequences of gamone 1, we established a method of isolation based on the finding that this glycoprotein can be concentrated by a Con A affinity column. Gamone 1 is extremely unstable and loses its biological activity once adsorbed to any of the columns that we tested. By using a Con A affinity column and native PAGE, we detected a 30-kDa protein corresponding to gamone 1 activity and determined the partial amino acid sequences of the four peptides. To isolate gamone 1 cDNA, we isolated mRNA from mating-type I cells stimulated by synthetic gamone 2 and then performed rapid amplification of cDNA ends procedures by using gene-specific primers and cloned cDNA of gamone 1. The cDNA sequence contains an ORF of 305 amino acids and codes a possibly novel protein. We also estimated the arrangement of sugars by comparing the affinity to various lectin columns.