NSF/MCB-BSF High-resolution mapping of the protein landscape in plant photosynthetic membranes

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Life on earth is fueled by photosynthesis, which converts sunlight into metabolic energy forms. In plants, photosynthetic energy conversion is realized by pigment-protein complexes that are harbored in highly specialized thylakoid membranes inside the chloroplasts. The dynamic response of the protein landscape in thylakoid membranes to unpredictable environmental changes (i.e. fluctuations in sunlight intensity by clouds, self-shading of leaves in wind) triggers photoprotective high-energy quenching (qE) that is essential for the survival of the plant. The project will map qE-induced protein landscape dynamics in thylakoid membranes with molecular resolution as a basis for understanding key photosynthetic functions. The intellectual merit of the proposed work is that it defines an innovative and complete pipeline of methods, ranging from state-of the art electron microscopy to coarse grain computer simulations, which will provide a quantitative understanding of photosynthetic light harvesting and electron transport. This pipeline will lead to urgently needed insights into dynamic structure-function relationships in thylakoid membranes. Furthermore, it is raising protein landscape analysis to a new level with unprecedented resolution to increase our in-depth understanding of photosynthetic energy conversion. The broader impact of the project is twofold: First, it will provide hands-on research experience to undergraduate students from underrepresented groups, and establish a new computer-based teaching tool for a computational chemistry course. Second, social benefits of the proposed work are expected for the improvement of crop plants and biofuel prospects since it turns out that optimization and adjustment of the qE mechanisms by bioengineering could be a powerful tool to increase plant performances. To generate high-resolution protein maps of the thylakoid protein landscape as basis to provide mechanistic understanding for the qE-dependent regulation of light-harvesting and electron transport, three specific aims will be pursued. Aim #1: Establishing high-resolution protein maps for different qE states. Plants will be examined using electron microscopy and compositional analysis which will lead to detailed coarse grain thylakoid protein landscapes. Aim #2: Determine how qE-induced changes in protein landscapes impact light harvesting and photoprotective qE. Coarse grain protein maps of thylakoid membranes will be used to model photosynthetic light harvesting in order to interpret measured data. Aim #3: Determine how qE-triggered switches in protein landscapes control diffusion dependent electron transport. A dynamic protein landscape model for the entire thylakoid membrane will be developed that allows simulation of the whole photosynthetic electron transport to understand in vivo data. This collaborative US/Israel project is supported by the US National Science Foundation and the Israeli Binational Science Foundation.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.