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Recent review highlights key new insights in Rubisco regulation to enhance crop productivity

Rubisco is the most abundant protein on Earth and plays a crucial role in the photosynthetic process that allows plants to grow and produce the food everything on Earth needs to survive. However, being incredibly important doesn’t mean it works incredibly well. In fact, Rubisco has been described as an inefficient enzyme. So much so that researchers such as Elizabete Carmo-Silva with the Realizing Increased Photosynthetic Efficiency (RIPE) Project have spent decades working on ways to improve its regulation and efficiency.

In the photosynthetic process, Rubisco is responsible for taking in CO2 and turning it into glucose and energy for the plant. This means it controls how much energy the plant has for making food and how quickly it can produce it. However, 25% of the time Rubisco mistakes O2 for CO2, creating a toxin for the plant rather than energy. This is often exacerbated under non-optimal environmental conditions such as heat and drought.

Considerable research over the last few decades has focused on how to improve this inefficient but essential enzyme. This is of particular interest under the current and future climate scenarios, where optimizing Rubisco usage processes (also known as regulation) can lead to improved photosynthesis and crop productivity. In a recent manuscript, published in New Phytologist, Carmo-Silva and two colleagues review the knowns and highlight the key insights of Rubisco regulation in crops.

“Decades of research have revealed the complexities of Rubisco regulation and shown that this is a highly integrated process that occurs in all plants,” said Carmo-Silva, Professor of Crop Physiology at Lancaster University. “The manuscript proposes key unknowns that should be addressed to inform effective strategies for improving crop yields and climate resilience.”

Previous research has been split into three categories based on how scientists approached Rubisco regulation: 1) Regulation by Rubisco Activase, 2) Regulation by climate-driven changes in the chloroplast stroma environment, and 3) new opportunities to enhance regulation, where the authors indicate future efforts should focus. One of the options that Carmo-Silva believes is a great opportunity, is to speed up the Rubisco response to changing environments.

“If we want to focus on improving crop yield and crop climate resilience, we should focus on the response to changes in light and increasing temperatures because those are two conditions where Rubisco activity is most limiting,” said Carmo-Silva. “Regulating Rubisco activity in plant leaves is crucial to maximizing the success of crop improvement approaches.”

Carmo-Silva leads the Rubisco research efforts for Realizing Increased Photosynthetic Efficiency (RIPE), an international research project that is engineering crops to be more productive by improving photosynthesis, the natural process all plants use to convert sunlight into energy and yields. Her work has been supported by the Bill & Melinda Gates Foundation, Foundation for Food & Agriculture Research, U.K. Foreign, Commonwealth & Development Office, and Bill & Melinda Gates Agricultural Innovations (Gates Ag One).

Compiling this review was important to Carmo-Silva professionally and personally. In addition to gathering all of the research in one place, she was able to do so with two women researchers who, like her, are native Portuguese speakers. Co-authors Joana Amaral and Ana KM Lobo are Carmo-Silva’s colleagues at the Lancaster Environment Centre.

Amaral and Lobo are part of European Union’s Horizon 2020 sister projects CAPITALISE (Combining Approaches for Photosynthetic Improvement To ALlow Increased Sustainability in European agriculture) and PhotoBoost (A holistic approach to improve the photosynthetic performance and productivity of C3 crops under diverse environmental conditions), respectively. Both projects aim to improve photosynthesis for higher-yielding crops in Europe (tomato, barley, maize, potato, and rice), while RIPE focuses on crops that are key sources of calories and protein in Sub-Saharan Africa (e.g., cowpea).

“This review combines the exciting discussion of relevant fundamental scientific papers and recent research approaches,” said Amaral. “We are thankful for the constructive feedback from reviewers and the editor and proud of the final result,” added Lobo. Tansley reviews are meant to be accessible and the three authors embraced the challenge of simplifying the complex regulation of Rubisco.