This project will study how calcium ions in cells sometimes undergo rapid oscillations in space and time during polar cell growth, a mechanism that is extremely important during pollen tube tip growth during plant fertilization, extension of fungal hyphae, and tumor cell metastasis. Spatiotemporal calcium ion image data will be collected from growing Arabidopsis pollen tubes and the investigators will undertake an iterative modeling-experimental testing approach, drawing on joint expertise from cell biologists, mathematicians and statisticians, aimed at discovering the unknown quantitative mechanisms that modulate rapid and directed pollen tube tip growth. The fundamental knowledge gained from this project may aid development for chemical or genetic disease treatment strategies, since cell polarization is involved in many human diseases and cancers. Results could assist with understanding fungal pathogens, because pollen tube tip growth is analogous to that of invasive fungal hyphae. This interdisciplinary project involves undergraduate, graduate students and postdoctoral trainees. Computational and simulation tools and theoretical results will be made publicly available to enable greater use and facilitate other researchers in these fields. This project is funded jointly by the Division of Mathematical Sciences Mathematical Biology Program, the Division of Molecular and Cellular Biosciences Cellular Dynamics and Function Program, and the Division of Integrative Organismal Systems Physiological Mechanisms and Biomechanics Program.
Calcium is of broad biological importance, needed not only for bone development but also as a signal to regulate a vast number of cellular processes such as polar cell growth. Intracellular calcium oscillation provides a key spatiotemporal calcium signal, but the underlying mechanisms regulating mechanisms remain largely unknown. The proposed project will use Arabidopsis pollen tube polar growth as a model system. Experimental data suggests that oscillatory pollen tube tip growth is controlled by the spatiotemporal oscillation of two intertwined key regulators: the ROP1 GTPase activity localized to the apical plasma membrane (cell boundary) and the tip-focused calcium gradient within the cell cytoplasm. To quantitatively elucidate these interdependent relationships and the underlying mechanism for the spatiotemporal oscillation of the system, we will develop a 2D calcium gradient model to characterize the formation of tip-focused intracellular calcium gradient and a reaction-diffusion activator-inhibitor system of ROP1 and calcium gradients that generate spatiotemporal oscillations. ROP1 and calcium dynamics will also be formulated in 3D to elucidate mechanistic linkage between rapid tip growth and growth redirection. The proposed research will establish new design principles underscoring rapid spatiotemporal oscillations that serve as a common regulatory mechanism and organize developmental strategies for many cell functions. This work will also characterize the quantitative mechanisms underlying the generation of calcium gradients and oscillations that are common calcium signals in all cellular organisms, with significant impact on a broad range of biological systems.
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.
