Examining the correlated molecular mechanisms of self and heterospecific pollen-pistil recognition

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Flowering plants display their charismatic flowers open and ready for pollinators or wind to bring pollen for reproduction. Determining how plants successfully reproduce requires understanding the molecular mechanisms underlying how female reproductive organs (pistils) recognize and accept high quality pollen while rejecting low quality pollen. The recognition between pistils and pollen is significant for two important mate choices in plants - distinguishing between self-pollen and non-self-pollen as well as between pollen from the same species and pollen from different species. This research investigates the molecular mechanisms underlying self-pollen reject and foreign-species pollen rejection in Phlox drummondii, a native Texas wildflower. In this species there is extensive natural variation in the ability of pistils to recognize and reject self and foreign pollen and the variation in these two recognition systems is highly correlated across individuals. This research involves a detailed genetic investigation of molecular mechanisms causing pollen-pistil recognition and the causes of the correlation between incompatibilities. Specifically, this research combines quantitative genetic dissection of variation in incompatibilities, with genome-wide gene expression analyses, and an artificial selection experiment to discover new mechanisms of pollen-pistil interactions in a species that has evolved self and foreign incompatibly independently of those found in model plant systems. This research will be complemented by outreach activities associated with the local natural history museum. The scientists will create educational activities for elementary and high school students, provide teacher professional development workshops about floral diversity, and organize public lectures on plant science. This project investigates the long-standing hypothesis that self and heterospecific pollen-pistil incompatibility systems are mechanistically linked by dissecting the molecular basis of variation in incompatibility within a non-model wildflower species. Specifically, this research will determine if self and heterospecific recognition share genetic mechanisms, if the breakdown of self and heterospecific incompatibility involves multiple genes including genes outside the self-identity locus, and if the correlation between self and heterospecific incompatibility could constrain the evolution of pollen-pistil recognition. To accomplish these goals, this research will determine the molecular mechanisms underlying incompatibly through whole-genome gene expression analyses, characterize the genetic architecture of the breakdown of self and heterospecific pollen recognition through genetic mapping experiments, and quantify the genetic constraint imposed by the correlation between incompatibilities using an artificial selection experiment. This integrative research will test specific hypotheses about the genetic basis of incompatibly in plants while discovering new mechanisms of pollen-pistil recognition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.