The carnivorous Venus flytrap uses prey-derived amino acid carbon to fuel respiration

The present study was performed to elucidate the fate of carbon (C) and nitrogen (N) derived from protein of prey caught by carnivorous Dionaea muscipula. For this, traps were fed ¹³ C/¹⁵ N-glutamine (Gln). The release of ¹³ CO₂ was continuously monitored by isotope ratio infrared spectrometry. After 46 h, the allocation of C and N label into different organs was determined and tissues were subjected to metabolome, proteome and transcriptome analyses. Nitrogen of Gln fed was already separated from its C skeleton in the decomposing fluid secreted by the traps. Most of the Gln-C and Gln-N recovered inside plants were localized in fed traps. Among nonfed organs, traps were a stronger sink for Gln-C compared to Gln-N, and roots were a stronger sink for Gln-N compared to Gln-C. A significant amount of the Gln-C was respired as indicated by ¹³ C-CO₂ emission, enhanced levels of metabolites of respiratory Gln degradation and increased abundance of proteins of respiratory processes. Transcription analyses revealed constitutive expression of enzymes involved in Gln metabolism in traps. It appears that prey not only provides building blocks of cellular constituents of carnivorous Dionaea muscipula, but also is used for energy generation by respiratory amino acid degradation.