AAT Gene Modulation in Tobacco for Lower Acrylamide Curing
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Solution Overview
Problem
The presence of elevated levels of free amino acids in tobacco during curing leads to the formation of acrylamide and undesirable odors in smoke and aerosol, posing health and quality concerns.
Innovation Solution
Modulation of aspartate transaminase (AAT) gene expression in Nicotiana tabacum using specific polynucleotide sequences to control amino acid biosynthesis, particularly during the curing process, thereby reducing the formation of acrylamide and sulfur odors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If amino acid content in tobacco is increased during curing, then the formation of acrylamide and sulfur odors in smoke and aerosol increases, but the flavor and quality of tobacco may be improved
Solution Approach 1:
The patent segments the amino acid metabolism pathway by targeting specific enzymes (asparagine synthetase, aspartate transaminase, cystathionine gamma-synthase) individually. By modifying specific genes in the pathway rather than applying a blanket reduction, the invention reduces harmful amino acids (asparagine, cysteine) while preserving or maintaining beneficial amino acids needed for tobacco flavor and quality.
Solution Approach 2:
The patent changes the biochemical parameters of amino acid metabolism by introducing modified enzymes with altered activity levels. The modified asparagine synthetase has reduced activity toward aspartate, modified aspartate transaminase has altered substrate specificity, and modified cystathionine gamma-synthase has reduced cysteine production, thereby changing the composition parameters of amino acids in cured tobacco.
2Object-affected harmful factors
If AAT gene expression is modulated to reduce aspartate levels, then acrylamide formation decreases, but other metabolic pathways may be affected
Solution Approach 1:
The patent applies segmentation by targeting specific isoforms and specific steps in the metabolic pathway. Instead of broadly affecting all amino acid metabolism, the modified AAT enzyme specifically affects the aspartate-glutamate transamination reaction, leaving other metabolic pathways intact. This selective targeting reduces acrylamide formation while maintaining metabolic stability.
Solution Approach 2:
The patent uses modified enzymes as intermediaries to control amino acid metabolism. The modified aspartate transaminase acts as an intermediary that redirects metabolic flux away from aspartate accumulation (which leads to acrylamide) while maintaining overall nitrogen metabolism through alternative pathways involving glutamate and other amino acids.
3Object-affected harmful factors
If multiple AAT genes are modified to reduce amino acid levels, then harmful metabolites decrease, but plant growth and agronomic performance may be impacted
Solution Approach 1:
The patent segments the genetic modification approach by targeting specific AAT genes (NtAAT1, NtAAT2, NtAAT3, NtAAT4) with different expression patterns and tissue specificities. By selecting and modifying only the AAT genes that are most active during curing (particularly NtAAT2 and NtAAT3), the invention reduces harmful metabolites while minimizing impact on plant growth, as other AAT genes continue to support normal metabolism.
Solution Approach 2:
The patent applies local quality by achieving amino acid modification specifically in the leaves during curing, rather than systemically throughout the entire plant. The modified AAT enzymes are expressed and active primarily in the leaf tissue where curing occurs, allowing localized reduction of harmful amino acids without broadly affecting plant growth and development.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Reduces acrylamide and ammonia levels in tobacco smoke and aerosol, maintaining nicotine levels, and minimizing agronomic impacts on plant growth, while allowing for the production of non-genetically modified plants.
Implementation Method 1
AAT catalyses the reversible transfer of the α-amino group between aspartate and glutamate, being therefore a key enzyme in amino acid metabolism by channeling nitrogen from glutamate and aspartate
Data Source
AI summary
The present invention discloses the polynucleotide sequences of genes encoding aspartate transaminase (AAT) from Nicotiana tabacum and the modulation of their expression. There is described a plant cell comprising: (i) a polynucleotide comprising, consisting or consisting essentially of a sequence having at least 80% sequence identity to SEQ ID NO: 1, SEQ ID NO: 3, SEQ ID NO: 5, SEQ ID NO: 7, SEQ ID NO: 9, SEQ ID NO: 11, SEQ ID NO: 13 or SEQ ID NO: 15; (ii) a polypeptide encoded by the polynucleotide set forth in (i); (iii) a polypeptide comprising, consisting or consisting essentially of a sequence having at least 95% sequence identity to SEQ ID NO: 6 or SEQ ID No: 8, at least 93% sequence identity to SEQ ID NO: 2 or SEQ ID NO: 10 or SEQ ID No: 12, or at least 94% sequence identity to SEQ ID NO: 4 or SEQ ID NO: 14 or SEQ ID NO: 16; or (iv) a construct, vector or expression vector comprising the isolated polynucleotide set forth in (i), wherein said plant cell comprises at least one modification which modulates the expression or activity of the polynucleotide or the polypeptide as compared to a control plant cell in which the expression or activity of the polynucleotide or polypeptide has not been modified.