The role of ELMOD family proteins and their genetic network in the development of specialized membrane domains on the Arabidopsis pollen surface

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In order for cells to correctly grow, divide and move, develop proper shapes, send signals to their neighbors, transport nutrients, and protect themselves, they often must direct certain molecules to specific regions on their surface. The resulting regions are known to be chemically distinct from the rest of the cellular surface, but how cells determine where to form these regions and what shape they should adopt is not well understood. To investigate these questions, this project will study pollen grains. Pollen has characteristic regions on its surface, called pollen apertures, which differ from the rest of the pollen surface and can be easily recognized under a microscope. Within a plant species, all apertures tend to develop at the same positions and acquire the same shape, whereas across plant species, aperture patterns often vary widely. In important crops such as corn and rice, pollen becomes sterile if apertures are missing. Thus, understanding how these regions form is important for control of plant reproduction. This project will focus on investigating what proteins are involved in aperture formation and what roles these proteins play in this process. The Broader Impacts of this project will include: a) the intrinsic merit of the research itself as apertures are important for plant reproduction; b) the training of several young scientists, from postdocs to undergraduate students, in methods of classical and molecular genetics, plant biology, microscopy, and biochemistry; and c) educating the general public about the importance of pollen in plant life cycle through a range of activities. To properly perform their functions, cells often form distinct domains in their plasma membranes, recruiting to these domains specific proteins, lipids, and other molecules. Yet the molecular mechanisms creating such domains are not well understood, particularly for plant cells. Specific regions on pollen surface devoid of the pollen wall exine, known as pollen apertures, are produced from the distinct aperture domains that form in the plasma membrane of the pollen precursor cells. Easily recognizable and quantifiable, pollen apertures present a powerful model for studying how plant cells form plasma membrane domains and how they select and specify sites where these domains would develop. Several members of the ENGULFMENT AND MOTILITY DOMAIN (ELMOD) protein family were recently found to be essential players in the process of aperture domain specification in Arabidopsis pollen, controlling the number and shape of aperture domains. Yet how ELMOD proteins promote formation of aperture domains and what molecular roles these proteins play in plant cells is completely unknown. Through a variety of genetic, biochemical, and imaging approaches, this project will define the roles of plant ELMOD proteins and identify members of the genetic network that function along with the ELMOD proteins in the specification of aperture domains.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.