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Sex determination driven by community cooperation
An optimized ratio of male and females in a sexually reproducing population helps to generate the genetic diversity useful to a species in a changing world. Tanaka et al. studied a fern in which the sex ratio is adjusted not by individual identity, but by signaling between individual plants (see the Perspective by Sun). Early-maturing individual ferns express some of the biosynthetic genes needed to make a precursor of the plant hormone gibberellin, which they secrete into the environment. Younger ferns, which express the enzymes needed to finalize synthesis of gibberellin, take up the signal and in response develop the organs that produce male gametes.
Abstract
Some ferns possess the ability to control their sex ratio to maintain genetic variation in their colony with the aid of antheridiogen pheromones, antheridium (male organ)–inducing compounds that are related to gibberellin. We determined that ferns have evolved an antheridiogen-mediated communication system to produce males by modifying the gibberellin biosynthetic pathway, which is split between two individuals of different developmental stages in the colony. Antheridiogen acts as a bridge between them because it is more readily taken up by prothalli than bioactive gibberellin. The pathway initiates in early-maturing prothalli (gametophytes) within a colony, which produce antheridiogens and secrete them into the environment. After the secreted antheridiogen is absorbed by neighboring late-maturing prothalli, it is modified in to bioactive gibberellin to trigger male organ formation.
