Surveying Rubisco diversity and temperature response to improve crop photosynthetic efficiency

Abstract

The threat to global food security of stagnating yields and population growth makes increasing crop productivity a critical goal over the coming decades. One key target for improving crop productivity and yields is increasing the efficiency of photosynthesis. Central to photosynthesis is Rubisco, which is a critical but often rate-limiting component. Here, we present full Rubisco catalytic properties measured at three temperatures for 75 plants species representing both crops and undomesticated plants from diverse climates. Some newly characterized Rubiscos were naturally "better" compared to crop enzymes and have the potential to improve crop photosynthetic efficiency. The temperature response of the various catalytic parameters was largely consistent across the diverse range of species, though absolute values showed significant variation in Rubisco catalysis, even between closely related species. An analysis of residue differences among the species characterized identified a number of candidate amino acid substitutions that will aid in advancing engineering of improved Rubisco in crop systems. This study provides new insights on the range of Rubisco catalysis and temperature response present in nature, and provides new information to include in models from leaf to canopy and ecosystem scale.

Acclimation of Biochemical and Diffusive Components of Photosynthesis in Rice, Wheat, and Maize to Heat and Water Deficit: Implications for Modeling Photosynthesis

“…The most commonly used “standard” Rubisco kinetics and temperature functions are those for tobacco as obtained by Bernacchi et al (2002). However, it is well documented that significant differences occur among species in Rubisco kinetics (e.g., Galmés et al, 2005, 2015; Savir et al, 2010; Orr et al, 2016; Prins et al, 2016), and these differences result in significant bias in model parameterization (Walker et al, 2013). These authors also indicate that in vitro Rubisco kinetics may not accurately describe the operation of Rubisco under physiological conditions, due to degradation and/or inactivation of the enzyme during extraction or differences in the in vitro assay conditions compared to the chloroplast stroma.…”

“…In contrast, measuring in vitro kinetic constants of Rubisco is easier and less time consuming, so that a number of different species can be characterized in a reasonable time (Hermida-Carrera et al, 2016; Orr et al, 2016; Prins et al, 2016). Therefore, we propose using Γ * derived from in vitro S c/o measured in each species at different temperatures to first estimate g m and, then, parameterize photosynthesis from A N -C c curves using the species and temperature specific in vitro kinetics of Rubisco rather than “standard” values determined for model species.…”

“…It is thus strongly recommended that the use of “standard” Rubisco kinetics from tobacco is avoided when modeling photosynthesis in other species. As obtaining in vivo Rubisco kinetics for different species is not achievable in the short-term, we propose to use in vitro kinetics as determined by the methods explained here and elsewhere (Kane et al, 1994; Ruuska et al, 1998; Parry et al, 2007; Shay and Kubien, 2013; Perdomo, 2015; Galmés et al, 2016; Orr et al, 2016; Prins et al, 2016) as a first proxy for in vivo kinetics.…”

Optimizing photorespiration for improved crop productivity

“…This trend is not observed in Form I Rubisco from diatoms, which contain a carbon concentrating mechanism and sustain near‐C3 levels of enzyme specificity and carboxylation turnover rates, in addition to much slower rates of oxygenation (Young et al ). This highlights the need to eliminate sampling bias towards crop plants and model species and survey Rubisco kinetic data from diverse sources to identify alternative evolutionary pathways to lower oxygenase activity (Orr et al ; Prins et al ). Implementing a non‐native Rubisco, such as a high‐specificity red algal or cyanobacterial version, into crop plants could offer a greater benefit than enhancing native Rubisco kinetics alone, particularly when coupled with a carbon‐concentrating mechanism (Zhu et al ; Lin et al ).…”

Photosynthesis: ancient, essential, complex, diverse … and in need of improvement in a changing world

“…Plant photosynthesis is limited by Rubisco (ribulose‐1,5‐bisphosphate carboxylase/oxygenase) activity much of the time due to its slow catalytic turnover, and concurrent oxygenase activity that competes with carbon fixation, especially in conditions of low chloroplastic CO 2 concentration and higher temperatures. That not all Rubiscos are identical has motivated work, reported at this meeting, on the extensive screening of natural diversity in Rubisco structure and kinetic properties (Galmés et al ., ; Whitney et al ., ; Hermida‐Carrera et al ., ; Orr et al ., ). Such characterization is essential to underpin attempts to tailor crops to future climates.…”