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Babaco mosaic virus BabMV induces defense metabolite production in papaya plants (Carica papaya)

Abstract:

While the physiological and molecular responses of plants to viral infections are well documented, the progressive metabolic changes at different stages of the infection and their functional implications are still poorly understood. Therefore, this study investigates the dynamics of metabolic changes in papaya plants infected with Babaco Mosaic Virus (BabMV). We inoculated papaya plants with BabMV and collected leaf samples at 2, 10, 15, and 30 days post-inoculation (dpi). A PCA analysis revealed a separation of metabolic profiles of the infection stages. Early metabolic responses to stress (primarily at 2–10 dpi) could be associated with the accumulation of sulfur-containing amino acids and phenolic compounds. As the response progresses, at late stages (15-30dpi) metabolic shifts toward stress-defense metabolites occur, particularly involving proline and polyamine biosynthetic pathway and their precursors, including glutamine, ornithine, and arginine. Upregulation of key biosynthetic enzymes e.g., glutamine synthetase and pyrroline-5-carboxylate synthase for proline synthesis, and ornithine decarboxylase and spermidine synthase for polyamine production, coupled with downregulation of catabolic enzymes such as proline dehydrogenase and polyamine oxidase. There was a notable rise in phenylalanine levels alongside increased phenylalanine ammonia-lyase (PAL) activity, providing an explanation for the observed increase of phenolics and flavonoids levels. This metabolic shift likely contributes to the accumulation of antioxidant metabolites crucial for the plant's defense response.