TY - JOUR

T1 - Towards a dynamic photosynthesis model to guide yield improvement in C4 crops

AU - Wang, Y.

AU - Chan, K.X.

AU - Long, S.P.

PY - 2021/7/31

Y1 - 2021/7/31

N2 - The most productive C4 food and biofuel crops, such as Saccharum officinarum (sugarcane), Sorghum bicolor (sorghum) and Zea mays (maize), all use NADP-ME-type C4 photosynthesis. Despite high productivities, these crops fall well short of the theoretical maximum solar conversion efficiency of 6%. Understanding the basis of these inefficiencies is key for bioengineering and breeding strategies to increase the sustainable productivity of these major C4 crops. Photosynthesis is studied predominantly at steady state in saturating light. In field stands of these crops light is continually changing, and often with rapid fluctuations. Although light may change in a second, the adjustment of photosynthesis may take many minutes, leading to inefficiencies. We measured the rates of CO2 uptake and stomatal conductance of maize, sorghum and sugarcane under fluctuating light regimes. The gas exchange results were combined with a new dynamic photosynthesis model to infer the limiting factors under non-steady-state conditions. The dynamic photosynthesis model was developed from an existing C4 metabolic model for maize and extended to include: (i) post-translational regulation of key photosynthetic enzymes and their temperature responses; (ii) dynamic stomatal conductance; and (iii) leaf energy balance. Testing the model outputs against measured rates of leaf CO2 uptake and stomatal conductance in the three C4 crops indicated that Rubisco activase, the pyruvate phosphate dikinase regulatory protein and stomatal conductance are the major limitations to the efficiency of NADP-ME-type C4 photosynthesis during dark-to-high light transitions. We propose that the level of influence of these limiting factors make them targets for bioengineering the improved photosynthetic efficiency of these key crops. © 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

AB - The most productive C4 food and biofuel crops, such as Saccharum officinarum (sugarcane), Sorghum bicolor (sorghum) and Zea mays (maize), all use NADP-ME-type C4 photosynthesis. Despite high productivities, these crops fall well short of the theoretical maximum solar conversion efficiency of 6%. Understanding the basis of these inefficiencies is key for bioengineering and breeding strategies to increase the sustainable productivity of these major C4 crops. Photosynthesis is studied predominantly at steady state in saturating light. In field stands of these crops light is continually changing, and often with rapid fluctuations. Although light may change in a second, the adjustment of photosynthesis may take many minutes, leading to inefficiencies. We measured the rates of CO2 uptake and stomatal conductance of maize, sorghum and sugarcane under fluctuating light regimes. The gas exchange results were combined with a new dynamic photosynthesis model to infer the limiting factors under non-steady-state conditions. The dynamic photosynthesis model was developed from an existing C4 metabolic model for maize and extended to include: (i) post-translational regulation of key photosynthetic enzymes and their temperature responses; (ii) dynamic stomatal conductance; and (iii) leaf energy balance. Testing the model outputs against measured rates of leaf CO2 uptake and stomatal conductance in the three C4 crops indicated that Rubisco activase, the pyruvate phosphate dikinase regulatory protein and stomatal conductance are the major limitations to the efficiency of NADP-ME-type C4 photosynthesis during dark-to-high light transitions. We propose that the level of influence of these limiting factors make them targets for bioengineering the improved photosynthetic efficiency of these key crops. © 2021 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

KW - C4 photosynthesis

KW - mathematical model

KW - photosynthetic induction

KW - PPDK regulatory protein

KW - Rubisco activase

KW - Saccharum officinarum

KW - Sorghum bicolor

KW - stomatal conductance

KW - Zea mays

KW - Carbon dioxide

KW - Crops

KW - Grain (agricultural product)

KW - Productivity

KW - Non-steady-state conditions

KW - Photosynthetic efficiency

KW - Photosynthetic enzymes

KW - Pyruvate phosphate dikinase

KW - Solar conversion efficiencies

KW - Temperature response

KW - Translational regulation

KW - Photosynthesis

U2 - 10.1111/tpj.15365

DO - 10.1111/tpj.15365

M3 - Journal article

VL - 107

SP - 343

EP - 359

JO - The Plant Journal

JF - The Plant Journal

SN - 0960-7412

IS - 2

ER -