Project description:Background: Tobacco leaves are the core raw materials for cigarette production, and their quality has direct and significant impacts on the sensory qualities of cigarette products. Cembrane diterpenoid alcohols are the main precursors of the aroma and fragrance components of tobacco leaves, accounting for approximately 60% of their chemical composition and considerably contributing to their aroma. Initially, we used ⁶⁰Co-γ radiation to induce mutagenesis in the tobacco wildtype variety, GDH64, to obtain the aphid-resistant mutant, MuGHD64. Cembrane diterpenoid alcohol levels were significantly increased in MuGHD64, indicating altered aromatic quality of its tobacco leaves. However, characteristic traits of and molecular mechanisms underlying the increased cembrane diterpenoid alcohol levels in MuGHD64 remain unknown. Therefore, MuGHD64 and GDH64 were investigated in this study. Results: Physiological and biochemical indicator levels were measured in MuGHD64 and GDH64, and transcriptome sequencing was performed to determine the mechanisms responsible for the increased cembrane diterpenoid alcohol levels in MuGHD64. Notably, cembratriene-ol and -diol levels were significantly higher in MuGHD64 than in GDH64. Additionally, MuGHD64 exhibited optimal chemical component levels and improved coordination. Its sensory quality indicators, such as aroma quality and intensity, sweetness, smoothness, and fineness, were superior to those of GDH64. Leaf surface secretory trichome density was significantly higher in MuGHD64 than in GDH64 at all stages. Levels of the cembrane diterpenoid alcohol metabolic precursors, isopentenyl and geranylgeranyl diphosphates, were also significantly higher in MuGHD64 than in GDH64. Transcriptome sequencing revealed that differentially expressed genes were mainly enriched in the metabolic processes related to terpenoid biosynthesis, sesquiterpenoid biosynthesis, isoprenoid biosynthesis, diterpenoid metabolism, diterpenoid biosynthesis, terpenoid skeleton biosynthesis, and plant hormone signal transduction. Cloning and sequencing of the cembratriene-ol synthase gene, NtCYC, revealed that the coding sequence of MuGHD64 harbored nucleotide substitutions at eight sites, resulting in six amino acid alterations. This significantly increased the gene expression levels, enhancing cembratriene-ol synthesis. Consequently, cembratriene-ol and -diol levels were significantly elevated, markedly improving the aroma quality of MuGHD64. Conclusions: Overall, this study revealed new genetic resources for the enhanced synthesis of cembratriene-ol, providing a foundation for breeding aroma-rich high-quality tobacco plants.

Project description:Comparative analysis of tobacco leaves transcriptomes unveils carotenoid pathway potentially determined the characteristics of aroma compounds in different environmental regions. Tobacco (Nicotiana tabacum) is a sensitive crop to environmental changes, and a tobacco with unique volatile aroma fractions always formed in specific ecological conditions. In order to investigate the differential expressed genes caused by environmental changes and reveal the formation mechanism of characteristics of tobacco in three different aroma tobacco regions of Guizhou Province, Agilent tobacco microarray was adapted for transcriptome comparison of tobacco leaves in medium aroma tobacco region Kaiyang and light aroma tobacco regions Weining and Tianzhu. Results showed that there was big difference among the gene expression profiles of tobacco leaves in different environmental conditions. A total of 517 differential expressed genes (DEGs) between Weining and Tianzhu were identified, while 733 and 1,005 genes differentially expressed between Longgang and another two tobacco regions Weining and Tianzhu, respectively. Compared with Longgang, up-regulated genes in Weining and Tianzhu were likely involved in secondary metabolism pathways, especially carotenoid pathway, including PHYTOENE SYNTHASE, PHYTOENE DEHYDROGENASE, LYCOPENE ε-CYCLASE, CAROTENOID β-HYDROXYLASE and CAROTENOID CLEAVAGE DIOXYGENASE 1 genes, while most down-regulated genes played important roles in response to temperature and light radiation, such as heat shock proteins. Gene Ontology and MapMan analyses demonstrated that the DEGs among different environmental regions were significantly enriched in light reaction of photosystem II, response of stimulus and secondary metabolism, suggesting they played crucial roles in environmental adaptation and accumulation of aroma compounds in tobacco plants. Through comprehensive transcriptome comparison, we not only identified several stress response genes in tobacco leaves from different environmental regions but also highlighted the importance of carotenoid pathway genes for characteristics of aroma compounds in specific growing regions. Our study primarily laid the foundation for further understanding the molecular mechanism of environmental adaptation of tobacco plants and molecular regulation of aroma substances in tobacco leaves.

Project description:Comparative analysis of tobacco leaves transcriptomes unveils carotenoid pathway potentially determined the characteristics of aroma compounds in different environmental regions. Tobacco (Nicotiana tabacum) is a sensitive crop to environmental changes, and a tobacco with unique volatile aroma fractions always formed in specific ecological conditions. In order to investigate the differential expressed genes caused by environmental changes and reveal the formation mechanism of characteristics of tobacco in three different aroma tobacco regions of Guizhou Province, Agilent tobacco microarray was adapted for transcriptome comparison of tobacco leaves in medium aroma tobacco region Kaiyang and light aroma tobacco regions Weining and Tianzhu. Results showed that there was big difference among the gene expression profiles of tobacco leaves in different environmental conditions. A total of 517 differential expressed genes (DEGs) between Weining and Tianzhu were identified, while 733 and 1,005 genes differentially expressed between Longgang and another two tobacco regions Weining and Tianzhu, respectively. Compared with Longgang, up-regulated genes in Weining and Tianzhu were likely involved in secondary metabolism pathways, especially carotenoid pathway, including PHYTOENE SYNTHASE, PHYTOENE DEHYDROGENASE, LYCOPENE ε-CYCLASE, CAROTENOID β-HYDROXYLASE and CAROTENOID CLEAVAGE DIOXYGENASE 1 genes, while most down-regulated genes played important roles in response to temperature and light radiation, such as heat shock proteins. Gene Ontology and MapMan analyses demonstrated that the DEGs among different environmental regions were significantly enriched in light reaction of photosystem II, response of stimulus and secondary metabolism, suggesting they played crucial roles in environmental adaptation and accumulation of aroma compounds in tobacco plants. Through comprehensive transcriptome comparison, we not only identified several stress response genes in tobacco leaves from different environmental regions but also highlighted the importance of carotenoid pathway genes for characteristics of aroma compounds in specific growing regions. Our study primarily laid the foundation for further understanding the molecular mechanism of environmental adaptation of tobacco plants and molecular regulation of aroma substances in tobacco leaves. In order to investigate the differential expressed genes caused by environmental changes and reveal the formation mechanism of characteristics of tobacco in three different aroma tobacco regions of Guizhou Province, Agilent tobacco microarray was adapted for transcriptome comparison of tobacco leaves in medium aroma tobacco region Kaiyang and light aroma tobacco regions Weining and Tianzhu.

			Action	DRS
	a_MTBLS14776_LC-MS_negative_hilic.txt	Txt
	a_MTBLS14776_LC-MS_positive_hilic.txt	Txt
	i_Investigation.txt	Txt
	m_MTBLS14776_LC-MS_negative_hilic_v2_maf.tsv	Tabular
	m_MTBLS14776_LC-MS_positive_hilic_v2_maf.tsv	Tabular

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