Function and mechanism of action of plant-specific LINC complexes in pollen tube and guard cell biology.

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This project explores the function of a new class of plant proteins that are involved in positioning the nucleus with the plant cell. The manner in which the position of the nucleus affects the function of plant cells is important for their life cycle and for their response to changing environmental conditions. This project will first explore the mechanisms by which nuclear position is controlled in the pollen tube, a structure that is essential for fertilization and thus the subsequent seed production in flowering plants. This project will also explore the role of the nuclear position in the cells that control the opening and closing of apertures (stomata) in the leaf of the plant, which regulate the movement of carbon dioxide from the air into the plant, and the loss of water (as vapor) from plant leaves into the air. The uptake of carbon dioxide from the air and the loss of water from the plant are of added significance in the face of increasingly frequent climate events such as drought, temperature extremes and the rising levels of carbon dioxide in the earth's atmosphere.Plant-specific outer nuclear envelope proteins (KASH proteins) are the functional equivalent of animal KASH proteins of the linker of nucleoskeleton and cytoskeleton (LINC) complexes. This project will dissect how KASH proteins function in plant male fertility and guard cell function. One plant specific LINC complex is required to move the vegetative nucleus through the pollen tube and its disruption affects pollen tube termination and male fertility. The connection of this newly discovered process to known signaling pathways of pollen tube function will be determined. A second plant-specific LINC complex is involved in anchoring the nucleus in guard cells and its disruption changes guard cell actin organization, abiotic stress responses, and guard cell dynamics. The connection between guard cell nuclear position, cortical actin patterns and aperture regulation by biotic and abiotic signals will be investigated. Mathematical modeling and targeted genetic and biochemical approaches will be used to identify the motors, clarify the force requirements and define the mechanisms that control nuclear movement in pollen tube and guard cells.