The function of lipid flippases in plant growth and thermotolerance

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A broader impact objective of this project is to develop crop plants that are more tolerant to heat stress. Climate change is expected to result in more frequent and severe periods of heat stress that will significantly reduce yields from agricultural crops. Simultaneously, projections indicate that world-wide food production must increase by more than 70% to feed an expected increase in the global human population to 10 billion by 2057. To meet the growing food demands it is critical that we develop crop plants that are more tolerant to heat stress conditions (i.e., the new normal). The proposed project aims to better understand how plants remodel their lipid membranes during heat stress, with a specific focus on a family of enzymes that flip lipids across membranes (lipid flippases). The research goals include engineering selected lipid flippases to be more active and testing whether these modified enzymes can accelerate the rate in which plants remodel their membranes to cope with changing temperatures. The research will determine whether this “faster membrane remodeling” strategy has any positive effect on plant growth, fertility, and seed yield under heat stress conditions. If successful, this technology could be applied to crop species and potentially improve yields under heat-stress conditions, thus strengthening global food-security in a warming world. Additionally, the research will provide a venue for teams of undergraduate student researchers to gain in-depth research experience in the field of plant biology. The long-term scientific goal is to understand the cellular functions of lipid flippases in eukaryotic cells and to use that knowledge to develop strategies to make crop plants more climate resilient. In plants, lipid flippases are referred to as ALAs (Aminophospho-Lipid ATPases, or P4-type ATPases) and these enzymes utilize ATP hydrolysis to catalyze the flipping of specific lipids from one side of the membrane to the other. Genetic knockouts of several ALAs in Arabidopsis result in plants that are hypersensitive to temperature changes. The central hypothesis guiding the research is that lipid flippases play critical roles in the rapid remodeling of membranes in response to changing temperatures. The first aim is to use domain swapping and site specific mutagenesis to identify important regulatory features within different ALAs. A key hypothesis to be tested is that variations in the C-terminal domain confer specific cellular functions, either by changing an ALA’s activity, regulation, localization, or substrate specificity. The second aim is to use lipidomics to quantify the abundance of specific lipids and determine whether a temperature-sensitive ala3 mutant has a defect in lipid remodeling during hot and cold temperature stresses. The third aim will determine whether the expression of a hyperactive ALA can improve vegetative growth or reproductive fitness under heat-stress conditions. The practical focus is to use recently gained knowledge on the C-terminal regulatory domains of ALAs to develop a novel strategy for improving thermotolerance in crop plants.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.