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Abstract Increase photorespiration and optimising intrinsic water use efficiency are unique challenges to photosynthetic carbon fixation at elevated temperatures. To determine how plants can adapt to facilitate high rates of photorespiration at elevated temperatures while also maintaining water‐use efficiency, we performed in‐depth gas exchange and biochemical assays of the C3extremophile,Rhazya stricta. These results demonstrate thatR. strictasupports higher rates of photorespiration under elevated temperatures and that these higher rates of photorespiration correlate with increased activity of key photorespiratory enzymes; phosphoglycolate phosphatase and catalase. The increased photorespiratory enzyme activities may increase the overall capacity of photorespiration by reducing enzymatic bottlenecks and allowing minimal inhibitor accumulation under high photorespiratory rates. Additionally, we found the CO2transfer conductances (stomatal and mesophyll) are re‐allocated to increase the water‐use efficiency inR. strictabut not necessarily the photosynthetic response to temperature. These results suggest important adaptive strategies inR. strictathat maintain photosynthetic rates under elevated temperatures with optimal water loss. The strategies found in R. stricta may inform breeding and engineering efforts in other C3species to improve photosynthetic efficiency at high temperatures.
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Increasing thermostability of the key photorespiratory enzyme glycerate 3‐kinase by structure‐based recombination
Summary As global temperatures rise, improving crop yields will require enhancing the thermotolerance of crops. One approach for improving thermotolerance is using bioengineering to increase the thermostability of enzymes catalysing essential biological processes. Photorespiration is an essential recycling process in plants that is integral to photosynthesis and crop growth. The enzymes of photorespiration are targets for enhancing plant thermotolerance as this pathway limits carbon fixation at elevated temperatures. We explored the effects of temperature on the activity of the photorespiratory enzyme glycerate kinase (GLYK) from various organisms and the homologue from the thermophilic algaCyanidioschyzon merolaewas more thermotolerant than those from mesophilic plants, includingArabidopsis thaliana. To understand enzyme features underlying the thermotolerance ofC. merolaeGLYK (CmGLYK), we performed molecular dynamics simulations using AlphaFold‐predicted structures, which revealed greater movement of loop regions of mesophilic plant GLYKs at higher temperatures compared to CmGLYK. Based on these simulations, hybrid proteins were produced and analysed. These hybrid enzymes contained loop regions from CmGLYK replacing the most mobile corresponding loops of AtGLYK. Two of these hybrid enzymes had enhanced thermostability, with melting temperatures increased by 6 °C. One hybrid with three grafted loops maintained higher activity at elevated temperatures. Whilst this hybrid enzyme exhibited enhanced thermostability and a similar Kmfor ATP compared to AtGLYK, its Kmfor glycerate increased threefold. This study demonstrates that molecular dynamics simulation‐guided structure‐based recombination offers a promising strategy for enhancing the thermostability of other plant enzymes with possible application to increasing the thermotolerance of plants under warming climates.
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- Award ID(s):
- 2030337
- PAR ID:
- 10560697
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Plant Biotechnology Journal
- Volume:
- 23
- Issue:
- 2
- ISSN:
- 1467-7644
- Format(s):
- Medium: X Size: p. 454-466
- Size(s):
- p. 454-466
- Sponsoring Org:
- National Science Foundation
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