The Evolution of Reproductive Development in Angiosperms

Evolutionary shifts in angiosperms have facilitated their dispersal and establishment throughout the world. It is believed that angiosperms have undergone extensive coevolution with the animal pollinator/ dispersal agents. As such, the evolutionary shift to fleshy edible fruit from dry dehiscent ones has occurred numerous times. Remarkably, despite the coevolutionary interdependence between plants and animals, the shift from outcrossing to self-mating has also been common. However, the molecular mechanisms that may underlie either of these shifts has not been established. In the Solanaceae (nightshades) and the Plantaginaceae, fleshy fruits and self-mating, respectively, have evolved multiple times. We investigated the potential molecular underpinning of these shifts using comparative sequence and expression analyses between pre- and post-transition taxa. FRUITFULL (euFUL) transcription factors have different roles in dry and fleshy fruit development. Our findings suggest that the coding sequence in some Solanaceae euFUL gene clades are evolving faster compared to their sister clades. In addition, we found evidence indicating a potential pseudogenization event in one of these clades. However, we were not able to detect any change in amino acid sequence associated with the transition to fleshy fruit. In the genus Collinsia (Plantaginaceae), multiple sister species pairs consist of an outcrosser and a selfer. A change in the developmental timing of the reproductive whorls underlies these evolutionary transitions to selfing. However, the molecular basis of this developmental phenomenon is unknown. We compared expression data across the entire floral development in the two sister taxa, the outcrossing C. linearis and the seling C. rattanii. Our data revealed there might be an association between putative metal ion binding proteins and the change in the developmental timing in C. rattanii. In addition, in agreement with a previous report, our results suggest that putative genes involved in pollen development and pollinator attraction are downregulated in C. rattanii