biostudies-literatureJardine KJU.S. Department of EnergyU.S. Department of Energy, Office of Science, Office of Biological and Environmental Research1132-1153https://www.ebi.ac.uk/biostudies/studies/S-EPMC12489301biostudies-literatureUnknown248(3)One-carbon (C₁) metabolism, centered on the universal methyl donor S-adenosyl methionine (SAM), plays critical roles in biosynthesis, redox regulation, and stress responses across plants and microbes. A recently proposed photosynthetic C₁ pathway links SAM methyl groups directly to RuBisCO-mediated CO₂ assimilation and integrates with nitrogen and sulfur metabolism. Light-dependent SAM synthesis may regulate the methylation of biopolymers and specialized metabolites and help mitigate photorespiratory stress under elevated temperature and drought. Phylogenetic analysis of two core enzymes suggests evolutionary continuity from methylotrophic microbes to land plants, supporting microbial origins via endosymbiotic gene transfer. Beyond intracellular roles, C<suThe New phytologistEvolutionary and functional relationships between plant and microbial C&lt;sub&gt;1&lt;/sub&gt; metabolism in terrestrial ecosystems.PMC12489301DE‐AC02‐05CH11231DE-AC02-05CH11231Honeker LKYang YRoscioli JZhang ZKwatcho Kengdo SRiley WJJardine KJfalseEvolutionary and functional relationships between plant and microbial C&lt;sub&gt;1&lt;/sub&gt; metabolism in terrestrial ecosystems.One-carbon (C₁) metabolism, centered on the universal methyl donor S-adenosyl methionine (SAM), plays critical roles in biosynthesis, redox regulation, and stress responses across plants and microbes. A recently proposed photosynthetic C₁ pathway links SAM methyl groups directly to RuBisCO-mediated CO₂ assimilation and integrates with nitrogen and sulfur metabolism. Light-dependent SAM synthesis may regulate the methylation of biopolymers and specialized metabolites and help mitigate photorespiratory stress under elevated temperature and drought. Phylogenetic analysis of two core enzymes suggests evolutionary continuity from methylotrophic microbes to land plants, supporting microbial origins via endosymbiotic gene transfer. Beyond intracellular roles, C<su2025-01-01T00:00:00Z2025 Nov2026-06-30T03:32:16.961Z2026-06-30T03:23:45.612ZS-EPMC124893014077240110.1111/nph.70434