Tobacco (Nicotiana tabacum), is a world’s major non-food agricultural crop widely cultivated for its economic value. Among several color change associated biological processes, plastid pigment metabolism is of trivial importance in postharvest plant organs during curing and storage. However, the molecular mechanisms involved in carotenoid and chlorophyll metabolism, as well as color change in tobacco leaves during curing, need further elaboration. Here, proteomic analysis at different curing stages (0 h, 48 h, 72 h) was performed in tobacco cv. Bi’na1 with an aim to investigate the molecular mechanisms of pigment metabolism in tobacco leaves as revealed by the iTRAQ proteomic approach. Our results displayed significant differences in leaf color parameters and ultrastructural fingerprints that indicate an acceleration of chloroplast disintegration and promotion of pigment degradation in tobacco leaves due to curing. In total, 5931 proteins were identified, of which 923 (450 up-regulated, 452 down-regulated, and 21 common) differentially expressed proteins (DEPs) were obtained from tobacco leaves. To elucidate the molecular mechanisms of pigment metabolism and color change, 19 DEPs involved in carotenoid metabolism and 12 DEPs related to chlorophyll metabolism were screened. The results exhibited the complex regulation of DEPs in carotenoid metabolism, a negative regulation in chlorophyll biosynthesis, and a positive regulation in chlorophyll breakdown, which delayed the degradation of xanthophylls and accelerated the breakdown of chlorophylls, promoting the formation of yellow color during curing. Particularly, the up-regulation of the chlorophyllase-1-like isoform X2 was the key protein regulatory mechanism responsible for chlorophyll metabolism and color change. The expression pattern of 8 genes was consistent with the iTRAQ data. These results not only provide new insights into pigment metabolism and color change underlying the postharvest physiological regulatory networks in plants, but also a broader perspective, which prompts us to pay attention to further screen key proteins in tobacco leaves during curing.

High-temperature stress is the main environmental stress that restricts the growth and development of woody plants, and the growth and development of woody plants are affected by high-temperature stress. The influence of high temperature on woody plants varies with the degree and duration of the high temperature and the species of woody plants. Woody plants have the mechanism of adapting to high temperature, and the mechanism for activating tolerance in woody plants mainly counteracts the biochemical and physiological changes induced by stress by regulating osmotic adjustment substances, antioxidant enzyme activities and transcription control factors. Under high-temperature stress, woody plants ability to perceive high-temperature stimuli and initiate the appropriate physiological, biochemical and genomic changes is the key to determining the survival of woody plants. The gene expression induced by high-temperature stress also greatly improves tolerance. Changes in the morphological structure, physiology, biochemistry and genomics of woody plants are usually used as indicators of high-temperature tolerance. In this paper, the effects of high-temperature stress on seed germination, plant morphology and anatomical structure characteristics, physiological and biochemical indicators, genomics and other aspects of woody plants are reviewed, which provides a reference for the study of the heat-tolerance mechanism of woody plants.

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.

Introduction: Flue-cured tobacco ( Nicotiana tabacum ) leaves exhibit substantial variation in oil content, yet the metabolic basis underlying these differences remains unclear. Methods: In this study, we integrated physicochemical measurements, ultrastructural observation, and metabolomic profiling to investigate oil-associated metabolic characteristics. High-oil and low-oil leaves from Tongren (TR; TRH, high-oil; TRL, low-oil) and Weining (WN; WNH, high-oil; WNL, low-oil) were analyzed. Results: High-oil leaves exhibited higher petroleum ether extract content (TRH 5.56%; TRL 4.63%; WNH 4.82%; WNL 4.15%) and lower softness value (TRH 34.7 mN; TRL 47.3 mN; WNH 21.7 mN; WNL 36.3 mN), with reduced luminosity (L*) and increased red-green axis (a*). Ultrastructural analysis revealed a greater abundance of lipid droplets in high-oil leaves, while starch granules persisted in low-oil leaves from TR. Metabolomic profiling identified 38 differential metabolites in TR (upregulated: triacylglycerols, phospholipids, fatty acid derivatives; downregulated: polyphenols, phenylpropanoids) and 47 in WN (upregulated: flavonoids, coumarins, sesquiterpene lactones; downregulated: organic acids, sugar alcohols, some fatty acid derivatives). Four metabolites—namely, marmesin, an arteannuin-like compound, isoferulic acid, and p-hydroxycinnamic acid—were found to be prevalent in both regions and exhibited a significant correlation with oil-related traits. Discussion: Pathway enrichment analysis further indicated that high-oil leaves from TR and WN displayed distinct metabolic patterns despite similar oil phenotypes. These findings suggest that oil accumulation is associated with region-distinct metabolic profiles and provide potential metabolic markers for oil-related quality improvement.

To clarify maturity-associated metabolic differences in flue-cured tobacco grown in distinct ecological regions of Guizhou and their relationships with post-curing style characteristics, middle leaves of Yunyan 87 were collected from Dafang County (DF) and Weining County (WN), representing honey-sweet and fresh-sweet regions, respectively, at 16 (T1), 18 (T2), 20 (T3), 22 (T4), and 24 (T5) days after topping. Leaf phenotypes, color parameters, SPAD values, key enzyme activities, and sensory style scores were assessed across the five stages, whereas widely targeted metabolomics was performed on cured leaves from T1 and T5, resulting in four metabolomic groups: DF_T1, DF_T5, WN_T1, and WN_T5. Local environmental and soil variables and RT-qPCR validation of selected pathway genes were incorporated to strengthen ecological and transcriptional interpretation. With delayed harvest, leaves from both regions changed from green to yellow-green and pale yellow, the midrib gradually lost greenness and turned whitish, and trichome shedding increased; these phenotypes appeared earlier in DF. SPAD values generally declined in both regions and remained higher in WN than in DF. POD, LOX, PPO, and SPS activities increased with maturity, with generally higher activities in DF. Sensory evaluation indicated that the target style characteristics of cured leaves from both regions were enhanced with increasing maturity. Widely targeted metabolomics of cured leaves identified 72 differential metabolites in DF between T5 and T1, including 44 upregulated and 28 downregulated metabolites, with high proportions of flavonoids, alkaloids, terpenoids, and other phenolic-related metabolites. In WN cured leaves, 51 differential metabolites were identified, including 19 upregulated and 32 downregulated metabolites, mainly associated with sugar metabolism, glutathione metabolism, flavonoid biosynthesis, and ABC transporters. Environmental correlation analysis suggested that radiation-, temperature-, precipitation-, and soil-related variables were associated with region-specific flavonoid and antioxidant-related metabolic patterns. RT-qPCR of selected flavonoid biosynthesis and sugar metabolism/transport genes in fresh leaves supported pathway-level transcriptional divergence, although partial transcription–metabolite decoupling was also observed. Collectively, these results reveal regional differences in physiological and metabolic remodeling at key maturity stages and provide preliminary metabolomics-based evidence for optimizing harvest timing and style-oriented quality regulation of flue-cured tobacco in Guizhou.

Yellowing is a critical post-harvest process that determines the flavor, quality, and economic value of crops, particularly tobacco (Nicotiana tabacum L.).