Towards the breeding of climate smart crops - Understanding plant acclimation to their environment

Abstract

Plants can adjust the biochemical processes in their existing organs and tailor them to their surrounding environment. This biochemical adjustment to a change in environmental condition is known as dynamic acclimation. The way in which plants dynamically acclimate their rates of photosynthesis and the downstream carbon metabolism to changes in temperature is poorly understood. With the aim of understanding, holistically, the coordinated changes in carbon uptake and utilization that encapsulate dynamic acclimation, I use both experimental and computational methods to assess the biochemical responses of mature Arabidopsis leaves to different temperature treatments. Arabidopsis leaves accumulate starch, malate and fumarate during the day and consume these carbon stores at night when the plant cannot photosynthesize. My measurements of photosynthetic parameters and diurnal metabolite concentrations show that the amount and the form of carbon stored in Arabidopsis leaves changes non-linearly with temperature. Fumarate, for example, has previously been shown to accumulate to a greater extent in the cold and was speculated to be a cold-sensor for photosynthetic acclimation. However, working across the full physiological temperature range of Arabidopsis, I observe an increased fumarate accumulation at both high and low temperatures. I use both kinetic and constraint-based metabolic modelling techniques to unveil how these changes in carbon metabolism in response to temperature support a photosynthetic acclimation response. I demonstrate how unbiased constraint-based methods, which do not require an objective function and thus minimize the observer bias imposed on the model, are particularly suited to studying dynamic acclimation of plants. Combining my own experimental data with existing omics data sets as model constraints, I propose the ratio of triose phosphate to 3-phosphoglycerate export from the chloroplast as a new metabolic signal for cold acclimation. Furthermore, I adapt a reliability engineering approach called Failure Mode and Effect Analysis to build a framework for studying the reliability of metabolism. Using this approach, I conclude that cytosolic fumarase, the enzyme responsible for fumarate accumulation in Arabidopsis leaves, acts as a fail-safe to carbon metabolism. Increased fumarate accumulation in response to extreme temperatures maintains system stability and is required for photosynthetic acclimation.

Date of Award	31 Dec 2020
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Royston Goodacre (Supervisor), Giles Johnson (Supervisor) & Jean-Marc Schwartz (Supervisor)