Proteomic and metabolic evaluation of lettuce (Lactuca sativa L.) fertilized with organic substrates from a composting

Compost material results from the digestion of organic matter by the action of the macro- and mesofauna, including different communities of microorganisms. The decomposition of organic matter generates leachate, a complex and balanced source of nutrition for plants, such as fruits and vegetables. Here, we describe the proteomic and metabolomic profiles of lettuce (Lactuca sativa L.) cultivated with mineral fertilizer, compost (at three dosages), and its leachate. Lettuce is the third most consumed vegetable by the Brazilian population, and its nutritional quality can be linked to the fertilizer used for its production. Its proteomics analysis resulted in an increased concentration of proteins related to photosynthesis, such as PSAD1 and PSAC, and the growth-linked protein FH4 in crops fertilized with compost compared to plants cultivated with mineral fertilizers. Metabolomics analysis showed changes in the TCA cycle (p < 0.003), pyruvate metabolism pathway (p < 0.004), glyoxylate and dicarboxylate metabolism (p < 0.009), and alanine, aspartate, and glutamate metabolism (p < 0.044) in leaves from compost-fertilized lettuce, indicating metabolic changes related to energetic metabolism. Our metabolomics and proteomics data show that compost fertilization improved plant growth, as this fertilization directly affected the proteins and metabolites involved in the photosynthesis process. Organic fertilizers can be an alternative for agriculture as they avoid using industrialized fertilizers, which can generate high costs for food production and enable the use of organic waste for food production, positively affecting the environment and the food chain.