Summary
Plants acclimate their photosynthetic capacity in response to changing
environmental conditions. In Arabidopsis thaliana, photosynthetic
acclimation to cold requires the accumulation of the organic acid
fumarate, catalysed by a cytosolic fumarase FUM2, however the role of
this is currently unclear.
In this study, we use an integrated experimental and modelling approach
to examine the role of FUM2 and fumarate across the physiological
temperature range. Using physiological and biochemical analyses, we
demonstrate that FUM2 is necessary for acclimation not only to low
temperatures, as previously shown, but also to increased temperature.
To understand the role of FUM2 activity, we have adapted a reliability
engineering technique, Failure Mode and Effect Analysis (FMEA), to apply
it to a biological problem. This allows us to formalize a rigorous
approach for ranking metabolites according to the potential risk they
pose to the metabolic system. FMEA identifies fumarate as a low-risk
metabolite. Its precursor, malate, is shown to be high-risk and liable
to cause system instability. We conclude that the role of cytosolic
fumarase, FUM2, is to provide a fail-safe, maintaining system stability
under changing environmental conditions.