Rubisco Activity and Thermal Response in Photosynthesis

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyses the primary carbon-fixation step of the Calvin–Benson cycle, converting atmospheric CO₂ into organic sugars. Despite its central role, Rubisco’s catalytic turnover is slow and its dual carboxylase/oxygenase activity imposes a trade-off between carbon assimilation and photorespiration. Photosynthetic efficiency is further constrained by the thermal sensitivity of both Rubisco and associated electron transport processes. Leaf-level CO₂ assimilation typically peaks at a modest optimum temperature (Topt) and declines at higher temperatures due to enzyme deactivation, altered membrane fluidity, increased photorespiratory losses and impairment of chloroplast electron transport. Understanding the interplay between Rubisco kinetics, its activation state and thermal response has become critical for modelling plant productivity under climate change, guiding crop improvement strategies and informing bioengineering approaches aimed at enhancing carbon fixation in diverse environments.

Research from Nature Portfolio

Recent studies have demonstrated that, across a broad range of higher plants, the decline in net CO₂ assimilation above Topt is accounted for by coordinated deactivation of Rubisco and reductions in chloroplast electron transport rate (J). A mechanistic model arises in which, in the absence of CO₂ supply limitations, rising leaf temperature predictably impairs both Rubisco activation state and J, thereby constraining photosynthetic flux under short-term heat stress.

Reconstruction and biochemical characterisation of ancestral Rubisco enzymes have revealed that ancient forms exhibited divergent evolutionary trajectories in specificity for CO₂ versus catalytic turnover rate. These studies indicate that thermal stability and catalytic efficiency have been shaped over geological timescales, providing a framework for understanding how modern Rubisco variants may be optimised for current and future temperature regimes.

Rubisco Activity and Thermal Response in Photosynthesis publication trend

The graph below shows the total number of articles in rubisco activity and thermal response in photosynthesis across all publications each year (not limited to Nature Index journals).

Technical terms

Rubisco: Ribulose-1,5-bisphosphate carboxylase/oxygenase, the key enzyme fixing CO₂ into organic carbon in the Calvin–Benson cycle.

Photorespiration: Process in which Rubisco oxygenates ribulose-1,5-bisphosphate, leading to CO₂ release and reduced photosynthetic efficiency.

Electron transport rate (J): Rate of electron flow through the photosynthetic electron transport chain, generating ATP and NADPH for carbon fixation.

Activation state: Fraction of Rubisco molecules in the carbamylated, catalytically competent form.

Topt: Optimal leaf temperature at which net CO₂ assimilation rate is maximised before thermal inactivation ensues.

References

1. Rubisco deactivation and chloroplast electron transport rates co-limit photosynthesis above optimal leaf temperature in terrestrial plants. Nature Communications (2023).
2. Biochemical characterization of predicted Precambrian RuBisCO. Nature Communications (2016).
3. The effect of increasing temperature on crop photosynthesis: from enzymes to ecosystems. Journal of Experimental Botany (2021).
4. Sensitivity and Responses of Chloroplasts to Heat Stress in Plants. Frontiers in Plant Science (2020).
5. Rubisco and Rubisco Activase Play an Important Role in the Biochemical Limitations of Photosynthesis in Rice, Wheat, and Maize under High Temperature and Water Deficit. Frontiers in Plant Science (2017).