Integrative metabolomics and proteomics analyses revealed that the improved curing process enhanced the quality of flue-cured tobacco

Tobacco is a widely cultivated economic crop globally, with the quality of flue-cured tobacco being closely linked to the curing process. In this study, we improved the curing process parameters for Yunyan 87 tobacco leaves and explored the effects of these treatments on tobacco curing. The improved curing process enhanced the visual and chemical quality of flue-cured tobacco leaves. Metabolomics and proteomics analyses revealed that the treatment upregulated the expression of proteins such as glycogen phosphorylase (PYG), alpha-amylase (AMY), and acid invertase (INV) in the tobacco leaves during the key stages of the curing process, which promoted the accumulation of sugars like glucose and fructose. Additionally, the treatment regulated the expression of key enzymes such as triosephosphate isomerase (TIM), fructose bisphosphate aldolase (ALDO), glutamine synthetase (glnA), and arogenate dehydratase (ADT) involved in glycolysis, the TCA cycle, and amino acid metabolism, fostering the synthesis of amino acids including L -glutamine, 4-aminobutyric acid, and L -phenylalanine. The flavonoid levels in flue-cured tobacco were correlated with protein expression in the biosynthesis of phenylpropanoids and flavonoids at the 42°C stage. This regulation of flavonoid synthesis and degradation was accompanied by the upregulation of carotenoid epsilon hydroxylase (LUT1) and zeaxanthin epoxide enzyme (ZEP), which increased carotenoid content. Our findings indicate that the treatment curing process enhance aroma precursors such as sugars, amino acids, flavonoids, and carotenoids in flue-cured tobacco. This process holds significant potential for the development of tobacco production and offers a theoretical foundation for optimizing both the tobacco curing process and tobacco quality.