PRIMARY STRUCTURE AND ORIGIN OF A PREDATOR RELEASED PROTEIN THAT INDUCES DEFENSIVE MORPHOLOGICAL-CHANGES IN EUPLOTES

The predatory ciliate Lembadion bullinum releases a chemical compound (L-factor) which induces morphological changes in another ciliate, Eup lotes octocarinatus, and some of its relatives. The changes render Eup lotes so extended that Lembadion has difficulties engulfing this prey. We have previously shown that the L-factor is a protein with a mass o f 31.5 kDa. Here we report the primary structure of the L-factor deduc ed from cDNA, the heterologous expression of the Lembadion gene encodi ng the L-factor, the production of an antibody directed against this f actor and the labeling of the cell surface of Lembadion with this anti body. From this and from peculiarities in the amino acid composition o f the L-factor we conclude that the L-factor is a surface protein of L embadion or at least a major part of it. To our knowledge the L-factor is the first kairomone whose origin and structure has been identified .