A mannose receptor-like molecule likely serves as the mate recognition pheromone receptor in the male rotifer Brachionus manjavacas
Couser, Laura M.
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Mate recognition in the male rotifer Brachionus manjavacas is controlled by contact chemoreception, which occurs when the male has a head-on encounter with a conspecific female. The female expresses a glycoprotein, the mate recognition pheromone or MRP, on her body surface that males detect with a receptor located in the male corona. A positive match between signal and receptor causes males to initiate mating behavior. After surveying the female B. manjavacas and male Brachionus plicatilis transcriptomes for all receptor genes, a C-type lectin gene was found which codes for a mannose receptor (MR). This gene is a good candidate for the MRP receptor because the MRP is glycosylated with mannose and mannose receptors recognize mannose/glucose oligosaccharides. Mannose has been found to block the binding of MR antibodies in males. In addition, mannose receptor immunostains show localized binding at the corona of males, but not in females. Mannose has also been shown to block circling, but binding of antibodies for the human mannose receptor does not decrease circling. A Western blot analysis of female rotifers shows that there is an MR in the female proteome; however, Western blots have not demonstrated binding of MR antibodies to male proteins. Mating bioassays showed that mannose is an important inhibitor of male mate recognition. These findings are best explained by the hypothesis that the male MRP receptor is an MR-like molecule that functions as a C-type lectin that is capable of binding of mannose.