Biochemical, Physiological and Transcriptomic Comparison between Burley and Flue-Cured Tobacco Seedlings in Relation to Carbohydrates and Nitrate Content

Abstract

Burley tobacco is a genotype of chloroplast-deficient mutant with accumulates high levels of tobacco-specific nitrosamines (TSNAs) which would induce malignant tumors in animals. Nitrate is a principle precursor of tobacco-specific nitrosamines. Nitrate content in burley tobacco was significantly higher than that in flue-cured tobacco. The present study investigated differences between the two tobacco types to explore the mechanisms of nitrate accumulation in burley tobacco. transcripts (3079) related to the nitrogen and carbon metabolism were observed. Expression of genes involved in carbon fixation, glucose and starch biosynthesis, nitrate translocation and assimilation were significantly low in burley tobacco than flue-cured tobacco. Being relative to flue-cured tobacco, burley tobacco was significantly lower at total nitrogen and carbohydrate content, nitrate reductase and glutamine synthetase activities, chlorophyll content and photosynthetic rate (Pn), but higher nitrate content. Burley tobacco required six-fold more nitrogen fertilizers than flue-cured tobacco, but both tobaccos had a similar leaf biomass. Reduced chlorophyll content and photosynthetic rate (Pn) might result in low carbohydrate formation, and low capacity of nitrogen assimilation and translocation might lead to nitrate accumulation in burley tobacco.

Identification of Milk Fat Metabolism-Related Pathways of the Bovine Mammary Gland during Mid and Late Lactation and Functional Verification of the ACSL4 Gene

“…Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis was achieved on KOBAS 3.0 [ 32 ]. R based on the hypergeometric distribution was operated to analyze not only GO terms but also KEGG pathways [ 33 ]. The calculation formula was as follows: (N represents the number of genes annotated in a pathway, n represents the number of DEGs in N, M represents the number of genes belonging to a particular pathway, and m represents the number of DEGs annotated in this particular pathway).…”

Oxidative stress-induced formation of covalently linked ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit dimer in tobacco plants

“…Burley is a mutant tobacco variety with characteristic yellow–green leaves. Although the genetic nature of this leaf phenotype remains unknown, it has been recently shown that key genes related to chlorophyll biosynthesis and photosynthesis are significantly down-regulated in burley plants and that this causes a decrease in chlorophyll content and a reduction of photosynthesis efficiency when compared to other tobacco varieties [24]. In previous studies, we have analyzed total protein extracts of other tobacco varieties (e.g., Petit Havana SR1) and of the model plant Arabidopsis exposed to oxidative stress and we did not observe any accumulation of covalently linked LSU dimer in total extracts [25–32].…”

Metabolome and molecular basis for carbohydrate increase and nitrate reduction in burley tobacco seedlings by glycerol through upregulating carbon and nitrogen metabolism

“…From our early study, we have found that nitrogen application was 5-folds higher in burley tobacco than in flue-cured tobacco to produce similar leaf biomass, and lower contents of pigment and energy substances and weaker nitrogen assimilation were the key factors contributing to nitrate accumulation in burley tobacco 7,8 . In this study, glycerol was applied to regulate carbohydrate and nitrate accumulation in two burley tobacco varieties.…”

“…In burley tobacco, high nitrate accumulation is correlated with nitrogen amount applied and reducing nitrogen level was effective in decreasing nitrate content 3 , although there is currently no in-depth coverage at molecular level in burley tobacco. From our early study, we have found that nitrogen application was 5-folds higher in burley tobacco than in flue-cured tobacco to produce similar leaf biomass, and lower contents of pigment and energy substances and weaker nitrogen assimilation were the key factors contributing to nitrate accumulation in burley tobacco 7 , 8 . In this study, glycerol was applied to regulate carbohydrate and nitrate accumulation in two burley tobacco varieties.…”

“…Nitrate is mainly accumulated during plant growth and development in the field 7 . Mostly, the low capacity of nitrogen assimilation and translocation lead to nitrate accumulation in burley tobacco 8 . Moreover, decreasing nitrate content in burley tobacco is always the important approach to lower the formation of TSNAs.…”