Abstract
Nornicotine is a secondary tobacco alkaloid that is produced by the N-demethylation of nicotine. Nornicotine production and accumulation in tobacco are undesirable because nornicotine serves as the precursor in the synthesis of the well characterized carcinogen N'-nitrosonornicotine during the curing and processing of tobacco. Although nornicotine is typically a minor alkaloid in tobacco plants, in many tobacco populations a high percentage of individuals can be found that convert a substantial proportion of the nicotine to nornicotine during leaf senescence and curing. We used a microarray-based strategy to identify genes that are differentially regulated between closely related tobacco lines that accumulate either nicotine (nonconverters) or nornicotine (converters) as the predominant alkaloid in the cured leaf. These experiments led to the identification of a small number of closely related cytochrome P450 genes, designated the CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines. RNA interference-induced silencing of the CYP82E2 gene family suppressed the synthesis of nornicotine in strong converter plants to levels similar to that observed in nonconverter individuals. Although each of the six identified members of the P450 family share >90% nucleotide sequence identity, sense expression of three selected isoforms revealed that only one (CYP82E4v1) was involved in the conversion of nicotine to nornicotine. Yeast expression analysis revealed that CYP82E4v1 functions as a nicotine demethylase. Identification of the gene(s) responsible for nicotine demethylation provides a potentially powerful tool toward efforts to minimize nornicotine levels, and thereby N'-nitrosonornicotine formation, in tobacco products.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 5
Claim · model-written summary
CYP82E2 family transcript levels were consistently higher in converter than nonconverter tobacco lines.
- Taxon
- tobacco
Nicotiana tabacume0 - Material
- convertere0
- Gene
- CYP82E2 familye0
- Outcome
- collective transcript levelse0
- Direction
- highere0
- Comparator
- nonconverter tobacco linese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines.”
Claim · model-written summary
Silencing the CYP82E2 family suppressed nornicotine synthesis in strong converter tobacco plants to nonconverter levels.
- Taxon
- tobaccoNicotiana tabacume1
- Material
- strong converter plantse0
- Treatment
- RNA interference-induced silencing of the CYP82E2 gene familye0
- Gene
- CYP82E2 gene familye0
- Outcome
- synthesis of nornicotinee0
- Direction
- suppressede0
- Comparator
- nonconverter individualse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RNA interference-induced silencing of the CYP82E2 gene family suppressed the synthesis of nornicotine in strong converter plants to levels similar to that observed in nonconverter individuals.”
t0“Nicotiana tabacum”
e1“CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines.”
Claim · model-written summary
The six identified P450 members share over 90% nucleotide sequence identity.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- P450 familye0
- Outcome
- nucleotide sequence identitye0
- Value
- >90%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“each of the six identified members of the P450 family share >90% nucleotide sequence identity”
t0“Nicotiana tabacum”
e1“CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines.”
Claim · model-written summary
Of three expressed isoforms, only CYP82E4v1 converted nicotine to nornicotine.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- CYP82E4v1e0
- Outcome
- conversion of nicotine to nornicotinee0
- Qualifier
- only onee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sense expression of three selected isoforms revealed that only one (CYP82E4v1) was involved in the conversion of nicotine to nornicotine.”
t0“Nicotiana tabacum”
e1“CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines.”
Claim · model-written summary
Yeast expression showed CYP82E4v1 functions as a nicotine demethylase.
- Taxon
- tobaccoNicotiana tabacume1
- Gene
- CYP82E4v1e0
- Outcome
- functions as a nicotine demethylasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Yeast expression analysis revealed that CYP82E4v1 functions as a nicotine demethylase.”
t0“Nicotiana tabacum”
e1“CYP82E2 family, whose collective transcript levels were consistently higher in converter versus nonconverter tobacco lines.”
The same questions in other papers
loss of function · molecular: metabolites · Nicotiana tabacum (tobacco)Positive and negative results
9 papers in the same direction as this paper · 14 in the opposite direction
- positive
- negative
- no effect
20 papers more in this group
See all 24 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.