Curing is an essential process for transforming tobacco leaves into an economic product. Optimizing curing parameters to regulate the orderly senescence and apoptosis of tobacco cells serves as a direct approach to enhancing the softness of leaves and a critical guarantee of quality. Therefore, understanding the intrinsic mechanisms underlying leaf softening during curing is vital for curing conditions and improving tobacco usability. To elucidate the degradation patterns of key cell wall components and dynamic changes in related enzyme activities during the softening of tobacco leaves during curing stage, we systematically analyzed the softening progression, cell wall structure, and dynamic transformation of key metabolites in the flue-cured variety Yunyan 87. The results demonstrated that leaf softness peaked during the yellowing stage (minimal softness value: 11.83mN). The cell wall structure progressively disintegrated throughout curing. Pectin methylesterase (PME), polygalacturonase (PG), and pectin lyase (PL) exhibited higher activities in fresh leaves and the yellowing stage, with corresponding values of 8.33 and 20.56 U/g for PME, 1.20 and 1.33 U/g for PG, and 2.39 and 4.93 U/g for PL. The cell wall matrix content decreased significantly during curing, reaching 412.84 mg/g in the drying stage.LC-MS/MS analysis identified 1,220 metabolites with significant alterations during curing, 54 of which were closely associated with cell wall metabolism. We further delineated metabolic pathways for cellulose, pectin, and lignin. This study comprehensively investigated the metabolic basis of tobacco leaf softening during curing, identifying the fresh leaves and yellowing stage as critical regulatory nodes. These findings provide valuable references for optimizing tobacco curing parameters.

Tobacco (Nicotiana tabacum) is a globally cultivated crop, with its quality closely associated with the color and chemical composition of cured tobacco leaves. In this experiment, the effects of spraying exogenous 2, 4-epibrassinolide (EBR) and melatonin (MT) on the development of tobacco leaves at maturity stage and the quality after curing were investigated. Both EBR and MT treatments significantly enhanced the appearance quality of tobacco leaves at the stem-drying stage. Following preharvest applications, the sugar-to-alkali ratio and potassium content increased, while the contents of starch, total alkaloids, and proteins decreased. The levels of conventional chemical components were improved, enhancing the overall coordination of the tobacco. Transcriptome analysis revealed that EBR treatment down-regulated the chlorophyll biosynthetic genes hemA, MgPEC, and ChlD, while up-regulating the chlorophyll degradation genes CHL2, SGR, and PAOs. Similarly, MT treatment down-regulated the chlorophyll biosynthetic genes FC2 and MgPEC and up-regulated the degradation genes CHL2 and SGR, thus promoting chlorophyll degradation. Furthermore, in the downstream carotenoid biosynthetic pathway, both EBR and MT treatments regulated abscisic acid-related genes, with NCEDs being up-regulated and CYP707A1s down-regulated, thereby promoting the leaf ripening. Metabolomics analysis indicated that EBR treatment primarily regulated alkaloids, terpenoids, and flavonoids, while MT treatment mainly affected flavonoids. Both treatments also reduced the accumulation of the harmful substance aristolochic acid B. Comprehensive evaluations of appearance quality, physiological parameters, transcriptome, and metabolomics analyses demonstrated that exogenous spraying of EBR and MT treatments improved the maturity and quality of cured tobacco leaves, with EBR treatment exhibiting a greater effect than MT treatment.

Green glutinous rice is a unique genetic germplasm that has yet to be adequately studied. This study investigated antioxidant capacity and flavonoid metabolites in the bran layer of green glutinous rice (LvH) compared to purple (HeiH), red (HongH) and white (GJG) varieties. The results showed that LvH bran had significantly higher content of total flavonoids and anthocyanin than that of HongH (1.91-fold and 4.34-fold) and GJG (2.45-fold and 13.30-fold). LvH bran also showed significantly higher levels of vitamin B1 and vitamin E than that of HeiH (1.94-fold and 1.15-fold) and HongH (1.22-fold and 1.13-fold), indicating that green glutinous rice bran was rich in bioactive components. LvH bran showed significantly lower IC₅₀ values for scavenging DPPH and ATBS radicals than GJG and even significantly lower IC₅₀ value for scavenging DPPH radicals than HongH, highlighting its potential as an effective source of antioxidants. LvH bran had significantly different downstream metabolite synthesis in the flavonoid pathway compared to HeiH, HongH, and GJG, with 40, 26, and 22 different metabolites, 23, 20, and 33 up-regulated differentially expressed metabolites (DEMs), and 73, 50, and 13 down-regulated DEMs, respectively. Of the 139 flavonoid metabolites identified in colored rice bran, 26 metabolites showed significant positive correlation with both ABTS and DPPH radical scavenging capacity. Typically, quercetin derivatives showed potential for evaluating the antioxidant capacity of colored rice bran. These findings offer valuable insights into the antioxidant properties of green glutinous rice bran and provide references for better understanding of flavonoid metabolites in different colored rice bran.

To clarify the relationships between the main chemical components in flue-cured tobacco in Guizhou and field meteorological factors during the tobacco growing period, the contributions of meteorological factors to the chemica... | Find, read and cite all the research you need on Tech Science Press

Microorganisms play a significant role in improving the flavor and quality of plant products. Analyzing how tobacco processing affects the microbial community structure is essential. Understanding the synergistic mechanisms of microorganisms during this process can help optimize the flavor and quality of plant products. In this study, samples were collected from four processing stages (T1: fresh leaves, T2: 42 °C, T3: 54 °C, T4: 68 °C), and metabolite and Phylloplane microbial data of tobacco leaves were generated. A comprehensive multi-omics analysis was conducted. The study shows that the increase in temperature and the decrease in humidity during the processing lead to the reorganization of the microbial community. Brevibacterium, Staphylococcus, Aspergillus, and Ganoderma were identified as core biomarkers. Bacteria dominate in the initial degradation of starch, while fungi promote the accumulation of soluble sugars through the transformation of intermediate products. This study deepens our understanding of the role of microorganisms and their carbohydrate metabolism in the tobacco leaf processing process and proposes a new strategy for constructing regulatory models by integrating multi-omics.

Saccharides critically influence tobacco quality. To elucidate the effects of postharvest shading (PS) pre-curing on saccharide metabolic flux, a targeted glycomics analysis was conducted. Compared to light exposure (CK), PS delayed chlorophyll degradation during pre-curing but accelerated yellowing, ultimately resulting in similar pigment levels. Additionally, PS inhibited photosynthesis, leading to reduced starch content and increased soluble sugar content before curing. Furthermore, PS altered the starch-to-sugar conversion, ultimately resulting in significantly higher soluble sugar content and lower starch content. Targeted glycomics analysis identified 21 saccharides, with glucose, D-fructose, and sucrose being dominant. Notably, PS ultimately increased glucose, D-fructose, and sucrose levels by 74.09%, 66.49%, and 17.36%, respectively. Pairwise comparisons revealed 6, 12, 5, 13, 10, and 11 differentially expressed metabolites before curing and at 38, 40, 42, 54, and 68 °C during curing, respectively, between PS and CK. Conjoint analysis identified methylgalactoside and three oligosaccharides (sucrose, raffinose, and maltose) as the central metabolites of saccharide metabolism during curing. D-mannose, D-sorbitol, and D-glucuronic acid were identified as biomarkers for assessing storage-induced metabolic perturbations using random forest algorithms. Collectively, these findings suggest that PS might enhance tobacco quality via carbohydrate metabolism modulation, providing a scientific basis for pre-curing protocol optimization and industrial application.