Abstract
Tabacco is the only plant known to biosynthesize large quantities of 3-methyl alkanes and 2-methyl alkanes.We investigated the δ 13C values of long-chain n-alkanes, 3-methyl and 2-methyl alkanes extracted from tobacco grown under chamber conditions to confirm the pathway used by the tobacco plant to synthesize these particular lipids.Tobacco was also grown under different environment(temperature, water availability and light) in order to obtain their δ 13C values for purpose of evaluating the isotope fractionation effects.The 3-methyl alkanes were found to have a predominant even-carbon number distribution(maximum at C32), whereas the 2-methyl alkanes exhibited an odd-carbon number distribution(maximum at C31).The 2-methyl alkanes were relatively more abundant than the 3-methyl alkanes and only two 3-methyl alkanes(aiC30 and aiC32) were observed.The δ 13C of the 3-methl alkanes were found to be enriched in 13C by an average of 2‰ compared to the n-alkanes and 2-methyl alkanes supporting a different biosynthetic precursor(2-methylbutanoyl C5-CoA precursor).The decarboxylation step probably led to the loss of a carboxyl group of the coenzyme A being depleted in 13C compared to the methyl group.The 2-methyl alkanes having an odd-numbered dominance are mainly biosynthesized from a 2-methyl-propanoyl(C4)-CoA biological precursor.The δ 13C of acetyl-CoA and methylpropanoyl(C4)-CoA precursors are probably similar.The similarity in the 13C of n-alkanes and the 2-methyl alkanes are consistent with this suggestion.Higher water availability generally results in more negative 13C bulk values, which was confirmed in the present study by δ 13C values of 2-methl alkanes, 3-methyl alkanes and n-alkanes lipids extracted from the tobacco leaves.Likewise, light intensity has been shown to influence plant bulk 13C values.The δ 13C of n-alkanes in tobacco grown under low-light conditions were about 2.2‰ more depleted in 13C than those lipids extracted from tobacco grown under elevated light conditions.A similar order of difference was observed for the 2-methl alkanes and 3-methyl alkanes(1.8‰ and 1.9‰ , respectively), the lipids from tobacco grown under low-light conditions being depleted in 13C.A negligible difference was observed for the 2-methyl alkanes and 3-methyl alkanes extracted from tobacco grown under elevated temperature.These results are consistent with the work of Farquhar(1980) where temperature appears to have only a minor effect on plant bulk 13C.
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Claims 13
Claim · model-written summary
The 3-methyl alkanes had a predominant even-carbon number distribution with a maximum at C32.
- Taxon
- tobacco
Nicotiana tabacumt0 - Outcome
- even-carbon number distributione1
- Value
- maximum at C32e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e1“The 3-methyl alkanes were found to have a predominant even-carbon number distribution(maximum at C32), whereas the 2-methyl alkanes exhibited an odd-carbon number distribution(maximum at C31)”
Claim · model-written summary
The 2-methyl alkanes had an odd-carbon number distribution with a maximum at C31.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- odd-carbon number distributione1
- Value
- maximum at C31e1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e1“The 3-methyl alkanes were found to have a predominant even-carbon number distribution(maximum at C32), whereas the 2-methyl alkanes exhibited an odd-carbon number distribution(maximum at C31)”
Claim · model-written summary
The 2-methyl alkanes were relatively more abundant than the 3-methyl alkanes.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- 2-methyl alkanese2
- Direction
- more abundante2
- Comparator
- 3-methyl alkanese2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e2“The 2-methyl alkanes were relatively more abundant than the 3-methyl alkanes and only two 3-methyl alkanes(aiC30 and aiC32) were observed”
Claim · model-written summary
Only two 3-methyl alkanes (aiC30 and aiC32) were observed.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- 3-methyl alkanese2
- Value
- twoe2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e2“The 2-methyl alkanes were relatively more abundant than the 3-methyl alkanes and only two 3-methyl alkanes(aiC30 and aiC32) were observed”
Claim · model-written summary
The delta 13C of the 3-methyl alkanes was on average about 2 per mil enriched compared with the n-alkanes and 2-methyl alkanes.
- Taxon
- tobaccoNicotiana tabacumt0
- Outcome
- δ 13C of the 3-methl alkanese3
- Direction
- enrichede3
- Value
- 2‰e3
- Comparator
- n-alkanes and 2-methyl alkanese3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e3“The δ 13C of the 3-methl alkanes were found to be enriched in 13C by an average of 2‰ compared to the n-alkanes and 2-methyl alkanes supporting a different biosynthetic precursor(2-methylbutanoyl C5-CoA precursor)”
Claim · model-written summary
The 3-methyl alkanes are supposed to be biosynthesised from a 2-methylbutanoyl C5-CoA precursor, a different precursor from the n-alkanes.
- Taxon
- tobaccoNicotiana tabacumt0
- Compound
- 2-methylbutanoyl C5-CoAe3
- Outcome
- biosynthetic precursore3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e3“The δ 13C of the 3-methl alkanes were found to be enriched in 13C by an average of 2‰ compared to the n-alkanes and 2-methyl alkanes supporting a different biosynthetic precursor(2-methylbutanoyl C5-CoA precursor)”
Claim · model-written summary
The 2-methyl alkanes with odd-numbered dominance are mainly biosynthesised from a 2-methyl-propanoyl (C4)-CoA precursor.
- Taxon
- tobaccoNicotiana tabacumt0
- Compound
- 2-methyl-propanoyl(C4)-CoAe4
- Outcome
- odd-numbered dominancee4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e4“The 2-methyl alkanes having an odd-numbered dominance are mainly biosynthesized from a 2-methyl-propanoyl(C4)-CoA biological precursor”
Claim · model-written summary
The decarboxylation step probably removed a carboxyl group of coenzyme A that is depleted in 13C relative to the methyl group (hypothesis).
- Taxon
- tobaccoNicotiana tabacumt0
- Compound
- coenzyme Ae5
- Outcome
- loss of a carboxyl groupe5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e5“The decarboxylation step probably led to the loss of a carboxyl group of the coenzyme A being depleted in 13C compared to the methyl group”
Claim · model-written summary
Tobacco grown under low light had n-alkane delta 13C values about 2.2 per mil more depleted than under elevated light.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- low-light conditionse6
- Outcome
- δ 13C of n-alkanese6
- Direction
- more depletede6
- Value
- 2.2‰e6
- Comparator
- elevated light conditionse6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e6“The δ 13C of n-alkanes in tobacco grown under low-light conditions were about 2.2‰ more depleted in 13C than those lipids extracted from tobacco grown under elevated light conditions”
Claim · model-written summary
Under low light, the delta 13C of 2-methyl alkanes was depleted by about 1.8 per mil.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- low-light conditionse7
- Outcome
- 2-methl alkanese7
- Direction
- depletede7
- Value
- 1.8‰e7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e7“A similar order of difference was observed for the 2-methl alkanes and 3-methyl alkanes(1.8‰ and 1.9‰ , respectively), the lipids from tobacco grown under low-light conditions being depleted in 13C”
Claim · model-written summary
Under low light, the delta 13C of 3-methyl alkanes was depleted by about 1.9 per mil.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- low-light conditionse7
- Outcome
- 3-methyl alkanese7
- Direction
- depletede7
- Value
- 1.9‰e7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e7“A similar order of difference was observed for the 2-methl alkanes and 3-methyl alkanes(1.8‰ and 1.9‰ , respectively), the lipids from tobacco grown under low-light conditions being depleted in 13C”
Claim · model-written summary
Higher water availability gave more negative delta 13C values in 2-methyl, 3-methyl and n-alkane lipids of tobacco leaves.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- Higher water availabilitye7
- Outcome
- δ 13C values of 2-methl alkanes, 3-methyl alkanes and n-alkanes lipidse7
- Direction
- more negativee7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e7“Higher water availability generally results in more negative 13C bulk values, which was confirmed in the present study by δ 13C values of 2-methl alkanes, 3-methyl alkanes and n-alkanes lipids extracted from the tobacco leaves”
Claim · model-written summary
Elevated temperature caused a negligible difference in the delta 13C of 2-methyl and 3-methyl alkanes.
- Taxon
- tobaccoNicotiana tabacumt0
- Treatment
- elevated temperaturee7
- Outcome
- 2-methyl alkanes and 3-methyl alkanese7
- Direction
- no_changeinferrede7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“tobacco leaves”
e7“A negligible difference was observed for the 2-methyl alkanes and 3-methyl alkanes extracted from tobacco grown under elevated temperature”
The same questions in other papers
heat · molecular: metabolites · Nicotiana tabacum (tobacco)Positive and negative results
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