Multi‐Omics Combined With Mitochondrial Feeding Assays Reveal a Novel Energy Metabolism Strategy for Floral Thermogenesis in Magnolia Driven by Synergistic Supply of Multiple Substrates

The high demand for energy during floral thermogenesis drives the synergistic operation of multiple energy substrates for the rapid temperature rise and successful reproduction of flowers. However, how thermogenic plants precisely regulate substrate supply and metabolic pathways within a short time to support large-scale energy and heat release remains a mystery. This study revealed the elaborate synergistic supply mechanism of multi-source substrates in Magnolia denudata during thermogenesis. Transcriptome analysis showed that genes related to the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS) were significantly upregulated during the thermogenic stage (S2). Mitochondrial feeding assays using isotopically labelled substrates revealed that during the thermogenic stage, both the amount of pyruvate imported via the mitochondrial pyruvate carrier (MPC) and NAD-malic enzyme (NAD-ME) increased, and their synergistic effect accelerated the metabolic flow of the TCA cycle. Targeted lipidomics analysis indicated that the content of 63.6% fatty acids in the fatty acid degradation pathway decreased, while the key enzyme genes involved in triacylglycerol lipase (TGL) and fatty acid β-oxidation pathways were highly expressed during the thermogenic stage. In addition, enhanced expression of genes related to alanine aminotransferase (AlaAT) and glutamate dehydrogenase (GDH) suggested that amino acid metabolism might provide additional substrates for thermogenesis. This study clarifies the synergistic energy supply of carbohydrate, fatty acid and amino acid metabolism during thermogenesis in M. denudata, providing new evidence for understanding the metabolic regulatory flexibility of floral thermogenesis in plants.