Abstract
Plants in natural environments receive light through sunflecks, the duration and distribution of these being highly variable across the day. Consequently, plants need to adjust their photosynthetic processes to avoid photoinhibition and maximize yield. Changes in the composition of the photosynthetic apparatus in response to sustained changes in the environment are referred to as photosynthetic acclimation, a process that involves changes in protein content and composition. Considering this definition, acclimation differs from regulation, which involves processes that alter the activity of individual proteins over short-time periods, without changing the abundance of those proteins. The interconnection and overlapping of the short- and long-term photosynthetic responses, which can occur simultaneously or/and sequentially over time, make the study of long-term acclimation to fluctuating light in plants challenging. In this review we identify short-term responses of plants to fluctuating light that could act as sensors and signals for acclimation responses, with the aim of understanding how plants integrate environmental fluctuations over time and tailor their responses accordingly. Mathematical modeling has the potential to integrate physiological processes over different timescales and to help disentangle short-term regulatory responses from long-term acclimation responses. We review existing mathematical modeling techniques for studying photosynthetic responses to fluctuating light and propose new methods for addressing the topic from a holistic point of view.
Highlights
Plants in natural environments are exposed to light and other environmental conditions that fluctuate on timescales ranging over orders of magnitude
As this review has shown, there is a gap between studies that consider short-term responses to changes in light conditions, and those that consider long-term acclimation processes
The photosynthetic apparatus is highly complex; understanding the regulatory networks of fluctuating light responses over time will require a deeper understanding of the system itself
Summary
Plants in natural environments are exposed to light and other environmental conditions that fluctuate on timescales ranging over orders of magnitude. A role for STN7-dependent phosphorylation was found in PSI photoprotection, through the maintenance of the redox stability of the electron transport chain (Grieco et al, 2012) Both STN7 and STN8 are capable of phosphorylating a range of proteins in the chloroplast (Schönberg et al, 2017), extending their involvement in the short-term response to fluctuating light onto further processes of acclimation. The relevance of NPQ as a long-term acclimation response to fluctuating light was recently shown using tobacco transgenic lines overexpressing PSBS and zeaxanthin epoxidase (ZEP) and violaxanthin de-epoxidase (VDE), the key enzymes in the xanthophyll cycle (Kromdijk et al, 2016) These plants showed a higher CO2 assimilation compared to the WT, leading to a higher dry mass accumulation under field conditions. Mechanistic models, albeit harder to construct, have several advantages over empirical models
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