Several projects in our laboratory center on the developmental genetics of plant reproduction, with an emphasis on cellular interactions during double fertilization. I will focus on the reception of the pollen tube by the synergid cells, where the pollen tube arrests growth and ruptures to release the sperm cells. We have isolated and characterized female gametophytic mutants that disrupt pollen tube reception. Pollen tubes that encounter such mutant female gametophytes are unable to rupture and release the sperm cells (Huck et al., Development 130:2149; Kessler et al., Science 330:968). These phenotypes suggest that the female gametophyte controls the behavior of the male gametophyte (pollen) in this process. One of the mutants, feronia, was shown to affect a receptor-like kinase (Escobar-Restrepo et al., Science 317:656), while another, nortia, disrupts a seven-transmembrane-domain-protein similar to the powdery mildew resistance protein Mlo (Kessler et al., Science 330:968). The identification of additional components in this signal transduction cascade suggest the involvement of glycosylation in this important recognition process. Furthermore, interspecific crosses between Brassicaceae can result in a similar phenotype, suggesting the cell-cell interactions during pollen tube reception may be involved in interspecific crossing barriers. Using genome-wide association studies, we have been able to identify ARTUMES, a factor that plays a specific role in interspecific compatibility while intraspecific crosses are not affected by mutations in this gene. Thus, pollen tube reception may be involved in establishing crossing barriers essential to maintain species boundaries similar to sperm-egg interactions in animals.