A Photosynthetic Link Between Carbon Assimilation, Nutrients, and Trace Gas Exchange

Plant C₁ metabolism is an important but still underappreciated part of plant function, connecting photosynthesis with nutrient use, stress responses, and the exchange of trace gases with the atmosphere. Although it plays a central role in plant growth and regulation, many questions remain about how C₁ compounds are produced, transported through the plant, and linked to other core metabolic processes.

In this talk, I will present evidence for an active oxidative C₁ pathway in plants, in which compounds such as methanol are converted stepwise to formaldehyde, formic acid, and CO₂, while also contributing to other important C₁ metabolic processes. I will also present recent work revealing a highly active photosynthetic C₁ pathway in poplar that appears to connect methyl-group metabolism directly with CO₂ assimilation, while also interacting with nitrogen and sulfur metabolism. I will discuss the idea that this pathway works together with photorespiration, may help plants cope with heat and drought stress, and may influence how plants regulate the chemical modification of many important biomolecules critical for growth and development.

Beyond its roles inside plant cells, C₁ metabolism also influences communication within plants and exchange with the atmosphere through the production of volatile compounds, including signaling molecules such as methyl salicylate, methyl jasmonate, and ethylene. Mobile C₁-related compounds such as S-methylmethionine and methionine may also help transport sulfur, nitrogen, and methyl groups through the plant, linking photosynthetic tissues in the canopy with non-photosynthetic tissues such as stems and roots.

I will further expand this framework to the rhizosphere, where roots may release a range of C₁ compounds and closely related metabolites, including methanol, formaldehyde, formic acid, methionine, and S-methylmethionine. These root-derived compounds may help link plant metabolism with microbial methylotrophy in soils, fueling microbial communities that consume single-carbon compounds and influencing nutrient cycling, trace gas exchange, and plant–microbe interactions belowground. This rhizosphere perspective suggests that plant C₁ metabolism may connect aboveground photosynthesis with belowground microbial processes in ways that have not yet been fully recognized.

Given its deep microbial ancestry and its production of diverse volatile compounds, C₁ metabolism may also offer a useful framework for thinking about much broader questions, including the origins of life and the search for biosignatures beyond Earth. I will briefly explore how C₁-based metabolism, because of its apparent antiquity and its links to volatile trace gases, may provide clues about early metabolic evolution as well as new ideas for detecting signs of life on exoplanets.

Using a new high-sensitivity laser spectrometer for C₁ gases together with complementary analytical tools, plant fumigation experiments, isotope labeling, nutrient limitation studies, and metabolomics, I will present recent progress and future plans to measure and manipulate these processes in real time in leaves, stems, roots, and their surrounding environments. Together, these studies suggest that plant C₁ metabolism is a major and underrecognized regulator of plant productivity, stress tolerance, and carbon and nutrient cycling on land, with implications that extend from the rhizosphere to planetary biology.