Using high-throughput 13CO2 labeling to determine if photorespiration can be engineered to increase flux to...

Photorespiration is connected to other aspects of plant metabolism, including one-carbon (C1) metabolism. While a major contributor of C1 units in leaves is serine, formate production through non-enzymatic decarboxylation of glyoxylate by H2O2 has been hypothesized to also contribute under some conditions. To determine if flux to C1 metabolism via formate can be increased through metabolic engineering, we developed a high throughput 13CO2 labeling system and used it to investigate wild-type (WT), catalase (cat) knockout, formate dehydrogenase (fdh) knockout, and fdh × cat double knockout Arabidopsis thaliana leaves. When fdh plants were labeled with 13C, there were no significant differences between fdh and WT plants in their C1 metabolites labeling kinetics. Additionally, the 13C labeling kinetics revealed that C1 metabolites were labeled more slowly in the cat and fdh × cat double mutant plants compared to WT plants, suggesting that formate production from glyoxylate is not a major contributor to C1 metabolism, nor can it be engineered to be so.