Analysis of proteins in conditioned medium that trigger monogonont rotifer mictic reproduction

The initiation, rate, duration, and termination of reproduction in the rotifer life cycle are tightly regulated, but the molecular mechanisms are poorly understood. Environmental signals are sensed and transduced to chemical signals within rotifers to integrate asexual and sexual reproduction. Crowding, diet, and photoperiod are environmental signals used by various rotifer species to initiate sexual reproduction, but most advances in the last 10 years have been in discovering how rotifer crowding is a case of quorum sensing. Female brachionids release a protein into their medium that acts as a pheromone and accumulates to trigger mictic reproduction. Candidates for this mixis-inducing protein (MIP) have been isolated from rotifer-conditioned medium and characterized biochemically. A N-terminal partial amino acid sequence of a particularly promising 39 kD protein was used to prepare a polyclonal antibody. This antibody immunoprecipitated a 22 kD protein from rotifer-conditioned medium and inhibited mixis induction. Future advances will benefit from the production of transgenic rotifers to confirm the mixis-inducing action of this putative MIP gene.