UC Riverside

Among flowering plants there have been frequent evolutionary transitions from an ancestral dry fruit to a derived fleshy fruit. These transitions have dramatic consequences since fleshy fruits often attract animals, including humans, that disperse these fruits and their seeds over large distances. Rarely, however, these transitions occur in reverse, shifting from fleshy back to dry fruits. We set out to better understand these transitions and their genetic basis. To enable more detailed studies, we developed a transformation protocol for Datura stramonium, a species whose dry fruit exemplifies this evolutionary reversion. We then complemented this protocol with a draft genome assembly of this plant and used this to show an increased mutation rate following transformation but negligible impact on gene expression. We also found evidence in D. stramonium for lineage-specific gene duplications in a pathway that synthesizes medicinally important tropane alkaloids. Next, we analyzed gene expression patterns over time in the pericarps of five species with differing fruit types. This revealed a core set of 121 genes with conserved patterns of expression among all species. These core fruit development genes contained a number of known developmental regulators but also implicated unexpected developmental pathways potentially involving brassinosteroids or small RNAs.