Cysteine-rich peptides promote interspecific genetic isolation in <i>Arabidopsis</i>

Abstract

Reproductive isolation is a prerequisite for speciation. Failure of communication between female tissues of the pistil and paternal pollen tubes imposes hybridization barriers in flowering plants. <i>Arabidopsis thaliana</i> LURE1 (AtLURE1) peptides and their male receptor PRK6 aid attraction of the growing pollen tube to the ovule. Here, we report that the knockout of the entire <i>AtLURE1</i> gene family did not affect fertility, indicating that AtLURE1-PRK6-mediated signaling is not required for successful fertilization within one <i>Arabidopsis</i> species. AtLURE1s instead function as pollen tube emergence accelerators that favor conspecific pollen over pollen from other species and thus promote reproductive isolation. We also identified maternal peptides XIUQIU1 to -4, which attract pollen tubes regardless of species. Cooperation between ovule attraction and pollen tube growth acceleration favors conspecific fertilization and promotes reproductive isolation.