Research Activity: Pollen tube growth delivers the sperm cells to the egg apparatus in higher plants, and is essential for sexual reproduction and food production. Because the growth rate oscillates, as do the underlying physiological processes, it is possible, using cross-correlation analysis, to determine if a process precedes or follows the change in growth rate. The main objective of this project is to focus on anticipatory events, because they are thought to represent primary regulators of growth.
Three apical events that anticipate increases in growth rate will receive attention as follows: increase in cell wall thickness, increase in pH in the alkaline band, and the oscillatory inward movement of endoplasmic reticulum (ER). As a working model it is suggested that secretion anticipates growth and accounts for the cell wall thickening, that changes in alkalinity modulate the structure of the actin cytoskeleton, and that changes in actin dictate the movement of ER and secretory vesicles.
Using different microscopic methods, including ratiometric ion imaging, fluorescence confocal imaging, and electron microscopy (EM), secretion, pH, and actin structure will be examined. Secretion dynamics will be probed using a pollen specific pectin methylesterase, linked to GFP. Oscillations in pH will be determined in cells injected with BCECF-dextran. Experimental modification of pH and/or the activity of the H+-ATPase will characterize the relationship of the alkaline band to growth. The structure of actin will be examined at the EM level. Finally, the activity of the actin cytoskeleton will be probed by examining the motion of ER.
Broader Impact: This project emphasizes the inclusion of underrepresented minorities as primary investigators in the research/discovery process. Dr. S. McKenna, who is a faculty member at Long Island University (LIU), where there are many minority students, is a Senior Collaborator. His involvement is two fold: firstly, as a researcher, he shares in the discovery process, and greatly improves the upward trajectory of his career. Secondly, as a mentor, he will help identify qualified minority students and engage them in research.
