We are involved in two research projects that involve fern gametophytes. One is to discover genes necessary and sufficient for sex determination in the fern Ceratopteris richardii. In this species, the sex of the gametophyte (male or hermaphroditic) is determined by the sex pheromone antheridiogen. It is secreted by hermaphrodites and induces young gametophytes to develop as males. Our second project is to understand how the fern Pteris vittata is able to tolerate and accumulate very high levels of the toxin arsenic. To discover sex determining genes in Ceratopteris and genes involved in arsenic tolerance in Pteris, we are currently using RNA-seq to identify genes differentially regulated by either the sex-determining pheromone or arsenic.