Improving photosynthetic metabolism for crop yields: what is going to work?

The last ten years has seen an enormous research effort in photosynthesis for crop improvement. Progress has been made in models Arabidopsis and tobacco, but demonstration of benefits in food security crops in field situations has been limited. Opinions are polarised whether the focus on photosynthesis is the right one. This article aims to develop a balanced way forward for photosynthesis research taking the view that bespoke improvements may be necessary depending on the crop and environment. Photosynthesis strongly affects the whole system with many interactions and feedbacks which must be considered in photosynthetic improvement. A recent paper (Yoon et al. 2020) overexpresses Rubisco in paddy rice with yield improvements up to 28% in field conditions. It is argued that this approach was successful because plants did not enter water deficit in the hydrated conditions and secondly nitrogen uptake was also increased to accompany increased carbon. In dry conditions combined with high light improved photoprotection may be a better strategy. For environments that experience intermittent mild to moderate drought representative of a lot of agriculture optimising source-sink may enable yield potential to be combined with resilience. To maximise benefits from photosynthesis research wider collaborations between teams from different backgrounds will be necessary to deliver success.