Cell-to-cell communication is the driving force behind successful reproduction in flowering plants. Extensive extracellular communication events occur between the male and female gametophytes during pollen tube reception to facilitate successful fertilization. These signaling events culminate into a product of great importance for both animals and plants: the seed. In this study, the pathogen defense regulator PATTERN-TRIGGERED IMMUNITY COMPROMISED RECEPTOR-LIKE CYTOPLASMIC KINASE 1 (PCRK1) was identified to function in pollen tube reception from both the male and female gametophytes in the flowering plant <i>Arabidopsis thaliana</i> using a forward genetic screen. A knockout of <i>pcrk1</i> suppresses the pollen tube overgrowth phenotype leading to infertility in <i>nortia</i> mutants. In addition, <i>pcrk1</i> pollen affected the pollen tube overgrowth phenotypes of pollen tube reception mutants <i>feronia</i> and <i>turan</i>. Shared molecular components of pollen tube reception and pathogen invasion have been reported. This study reveals another link between pathogen defense and pollen tube reception. By studying the links between fertility and disease in plants, we may be able to uncover potential trade-offs with fertility when breeding for pathogen resistance.<br>

Fertilization, both in plants and animals, is at its core, a study of cell to cell communication. With respect to plants, the male gametophyte, the pollen tube, elongates within the female organ called the pistil, transporting in its cytoplasm two sperm cells. The pollen tube is attracted by signals secreted from the synergid cells that are located at the entrance to the female gametophyte that resides in the ovule. Secondary pollen tube visitors to the ovules are unwanted and repelled presumably by signals emitted by the fertilized female. The final communication between the pollen tube and female gametophyte is the induction of pollen tube rupture upon penetration of the synergid cell, an event that leads to the release of the two sperm cells, which go on to fertilize the central cell and egg cell within the female gametophyte, completing a double fertilization process that is unique to plants. My thesis research is centered on elucidating the mechanism behind the synergid cell-induced pollen tube rupture process. Studies in our laboratory have established that the synergid cell-expressed receptor like kinase, called FERONIA, mediates a highly oxidative environment in the female gematophyte that is necessary for the pollen tube rupture process. Using an in vitro pollen tube culture system, my research showed that reactive oxygen species (ROS) induces pollen tube rupture in a Ca2+-dependent manner. My results suggests a careful and truly fascinating, though still hypothetical, design of a two molecule, FERONIA and ROS, two step activation system that uses ROS to prime the pollen tube outside the synergid cell, then expose it to calcium within the synergid cell to ensure that pollen tube rupture happens in the synergid cell, enabling fertilization.