Abstract
There have been many attempts to increase concentrations of the nutritionally essential sulphur amino acids by modifying their biosynthetic pathway in leaves of transgenic plants. This report describes the first modification of cysteine biosynthesis in developing seeds; those of the grain legume, narrow leaf lupin (Lupinus angustifolius, L.). Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS), the immediate product of SAT, and up to 26-fold in free cysteine, resulting in some of the highest in vivo concentrations of these metabolites yet reported. Despite the dramatic changes in free cysteine in developing embryos of SAT overexpressers, concentrations of free methionine in developing embryos, and the total cysteine and methionine concentrations in mature seeds were not significantly altered. Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development, and no increase in mature seed total sulphur amino acids compared with controls lacking SAT overexpression. The data support the view that the cysteine biosynthetic pathway is active in developing seeds, and indicate that SAT activity limits cysteine biosynthesis, but that cysteine supply is not limiting for methionine biosynthesis or for storage protein synthesis in maturing lupin embryos in conditions of adequate sulphur nutrition. OAS and free methionine, but not free cysteine, were implicated as signalling metabolites controlling expression of a gene for a cysteine-rich seed storage protein.
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Claims 11
Claim · model-written summary
SAT expression increased OAS concentration up to fivefold in developing lupin embryos.
Verbatim
e0“Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS)”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
SAT expression increased free cysteine up to 26-fold in developing lupin embryos.
Verbatim
e0“Expression in developing lupin embryos of a serine acetyltransferase (SAT) from Arabidopsis thaliana (AtSAT1 or AtSerat 2;1) was associated with increases of up to 5-fold in the concentrations of O-acetylserine (OAS), the immediate product of SAT, and up to 26-fold in free cysteine”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
Free methionine in developing embryos was not significantly altered in SAT overexpressers.
Verbatim
e0“Despite the dramatic changes in free cysteine in developing embryos of SAT overexpressers, concentrations of free methionine in developing embryos, and the total cysteine and methionine concentrations in mature seeds were not significantly altered”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
Total cysteine and methionine concentrations in mature seeds were not significantly altered.
- Taxon
- narrow leaf lupint0
- Organ / stage
- mature seedse0
- Outcome
- total cysteine and methionine concentrationse0
- Direction
- not significantly alterede0
Not reportedMaterial
Verbatim
e0“the total cysteine and methionine concentrations in mature seeds were not significantly altered”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
Segregating F2 seeds with SAT and storage protein transgenes had increased OAS during development.
Verbatim
e0“Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
The same segregating seeds had increased free cysteine during development.
Verbatim
e0“Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
The segregating seeds did not show increased free methionine during development.
Verbatim
e0“Pooled F(2) seeds segregating for the SAT transgene and for a transgene encoding a methionine- and cysteine-rich sunflower seed storage protein also had increased OAS and free cysteine, but not free methionine, during development”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
The segregating seeds had no increase in mature seed total sulfur amino acids relative to controls lacking SAT overexpression.
Verbatim
e0“no increase in mature seed total sulphur amino acids compared with controls lacking SAT overexpression”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
The authors infer that SAT activity limits cysteine biosynthesis in developing seeds.
Verbatim
e0“The data support the view that the cysteine biosynthetic pathway is active in developing seeds, and indicate that SAT activity limits cysteine biosynthesis”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
The authors infer that cysteine supply does not limit methionine or storage protein synthesis under adequate sulfur nutrition.
Verbatim
e0“cysteine supply is not limiting for methionine biosynthesis or for storage protein synthesis in maturing lupin embryos in conditions of adequate sulphur nutrition”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”
Claim · model-written summary
OAS and free methionine, but not free cysteine, were implicated in regulation of a cysteine rich storage protein gene.
Verbatim
e0“OAS and free methionine, but not free cysteine, were implicated as signalling metabolites controlling expression of a gene for a cysteine-rich seed storage protein”
t0“narrow leaf lupin (Lupinus angustifolius, L.)”