The -Gene Pleiotropically Determines Male Mating Type and Pollen Size in Heterostylous (Passifloraceae): A Novel Neofunctionalization of the YUCCA Gene Family.

In heterostylous, self-incompatible species, a member of the gene family, , resides at the -locus and has been hypothesized to determine the male mating type. gene family members synthesize the auxin, indole-3-acetic acid, via a two-step process involving the gene family. Consequently, it has been speculated that differences in auxin concentration in developing anthers are the biochemical basis underlying the male mating type. Here, we provide empirical evidence that supports this hypothesis. Using a transgenic knockdown approach, we show that acts pleiotropically to control both the male physiological mating type and pollen size, but not the filament length dimorphism associated with heterostyly in . Using qPCR to assess expression in different transgenic lines, we demonstrate that the level of knockdown correlates with the degree of change observed in the male mating type. Further assessment of expression through anther development, in the knockdown lines, suggests that the male mating type is irreversibly determined during a specific developmental window prior to microsporogenesis, which is consistent with the genetically sporophytic nature of this self-incompatibility system. These results represent the first gene controlling male mating type to be characterized in any species with heterostyly.