Fig. 1

Structure of the Huntiella α- and a-factor pheromones. A The α-factor pheromone is initially translated as a large pre-protein, possessing a signal peptide (indicated in red) and harboring numerous repeats of the mature pheromone (indicated in green). This protein is subsequently cleaved by a variety of enzymes, including STE13 (cleavage site indicated in yellow), and KEX1/2 (cleavage site indicated in orange), which release the individual mature pheromone factors. The structure of the Huntiella α-factor is similar to the structure of the canonical ascomycete α-factor. B The Huntiella a-factor is translated as a short peptide and also harbors numerous repeats (indicated in blue), each ending in a conserved CpaX domain (indicated in yellow). The Huntiella a-factor is comparable to the a-factor from Fusarium [23] and the h-type pheromone from Verticillium and Trichoderma [24]. However, it is quite different from the canonical ascomycete a-factor, which typically possesses only a terminal CAAX domain. This terminal CAAX domain is modified during pheromone maturation. Given the unique structure of the Huntiella a-factor pheromone, it is unknown whether additional processing of this pheromone takes place