Abstract
To inhibit expression specifically in the phloem, a 274-bp fragment of a cDNA (Gln1-5) encoding cytosolic glutamine synthetase (GS1) from tobacco was placed in the antisense orientation downstream of the cytosolic Cu/Zn superoxide dismutase promoter of Nicotiana plumbaginifolia. After Agrobacterium-mediated transformation, two transgenic N. tabacum lines exhibiting reduced levels of GS1 mRNA and GS activity in midribs, stems, and roots were obtained. Immunogold labeling experiments allowed us to verify that the GS protein content was markedly decreased in the phloem companion cells of transformed plants. Moreover, a general decrease in proline content in the transgenic plants in comparison with wild-type tobacco was observed when plants were forced to assimilate large amounts of ammonium. In contrast, no major changes in the concentration of amino acids used for nitrogen transport were apparent. A (15)NH(4)(+)-labeling kinetic over a 48-hr period confirmed that in leaves of transgenic plants, the decrease in proline production was directly related to glutamine availability. After 2 weeks of salt treatment, the transgenic plants had a pronounced stress phenotype, consisting of wilting and bleaching in the older leaves. We conclude that GS in the phloem plays a major role in regulating proline production consistent with the function of proline as a nitrogen source and as a key metabolite synthesized in response to water stress.
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Claims 7
Claim · model-written summary
Two transformed lines showed reduced GS1 mRNA and GS activity.
- Taxon
- N. tabacum
Nicotiana tabacume0 - Material
- two transgenic N. tabacum linese0
- Treatment
- transgenice0
- Gene
- GS1e0
- Outcome
- GS1 mRNA and GS activitye0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“two transgenic N. tabacum lines exhibiting reduced levels of GS1 mRNA and GS activity in midribs, stems, and roots were obtained”
Claim · model-written summary
GS protein declined in phloem companion cells of transformed plants.
- Taxon
- tobaccoNicotiana tabacume1
- Organ / stage
- phloem companion cellse0
- Treatment
- transformed plantse0
- Gene
- GSe0
- Outcome
- GS protein contente0
- Direction
- markedly decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GS protein content was markedly decreased in the phloem companion cells of transformed plants”
e1“wild-type tobacco”
Claim · model-written summary
Transgenic plants had less proline under high ammonium assimilation than wild-type tobacco.
- Taxon
- tobaccoNicotiana tabacume0
- Treatment
- transgenic plantse0
- Outcome
- proline contente0
- Direction
- decreasee0
- Qualifier
- large amounts of ammoniume0
- Comparator
- wild-type tobaccoe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a general decrease in proline content in the transgenic plants in comparison with wild-type tobacco was observed when plants were forced to assimilate large amounts of ammonium”
Claim · model-written summary
Transport amino acid concentrations showed no major change.
- Taxon
- tobaccoNicotiana tabacume1
- Treatment
- transgenic plantse1
- Outcome
- concentration of amino acids used for nitrogen transporte0
- Direction
- no major changese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no major changes in the concentration of amino acids used for nitrogen transport were apparent”
e1“a general decrease in proline content in the transgenic plants in comparison with wild-type tobacco was observed when plants were forced to assimilate large amounts of ammonium”
Claim · model-written summary
Labeling linked reduced proline production to glutamine availability.
- Taxon
- tobaccoNicotiana tabacume1
- Compound
- glutaminee0
- Outcome
- decrease in proline productione0
- Qualifier
- glutamine availabilitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decrease in proline production was directly related to glutamine availability”
e1“wild-type tobacco”
Claim · model-written summary
After salt treatment transgenic plants displayed wilting and bleaching of older leaves.
- Taxon
- tobaccoNicotiana tabacume1
- Material
- transgenic plantse0
- Organ / stage
- older leavese0
- Treatment
- salt treatmente0
- Outcome
- wilting and bleachinge0
- Value
- 2 weekse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 2 weeks of salt treatment, the transgenic plants had a pronounced stress phenotype, consisting of wilting and bleaching in the older leaves”
e1“wild-type tobacco”
Claim · model-written summary
The authors conclude that phloem GS regulates proline production.
- Taxon
- tobaccoNicotiana tabacume1
- Organ / stage
- phloeme0
- Gene
- GSe0
- Outcome
- proline productione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GS in the phloem plays a major role in regulating proline production”
e1“wild-type tobacco”
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