Abstract
Glutamine synthetase (GS; EC 6.3.1.2) is a key enzyme of ammonia assimilation in higher plants. In the present study the subunit composition and localization of GS in germinating barley (Hordeum vulgare) seed have been clarified. Analysis of the GS polypeptide composition by immunoblotting revealed two different polypeptides. A and B, with a molecular mass of 42 and 40 kDa, respectively. In the scutellum subunit A was already present in the ungerminated seed and remained unchanged, whereas subunit B appeared on day 2 and increased about 5-fold during germination. Polypeptide B also appeared later during germination in the aleurone layer, roots and weakly in the etiolated shoots. By immunogold microscopy, GS was detected in the scutellum and the aleurone layer of barley seeds during germination. Subcellular localization of GS on ultrathin cryosections showed that a cytosolic isozyme was present in the scutellum. Our study confirms that only a cytosolic GS is expressed in barley seed, and its subunit composition changes during germination.
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Claims 7
Claim · model-written summary
Barley germinating seeds contained two GS polypeptides, A at 42 kDa and B at 40 kDa.
Not reportedTaxon
Verbatim
e0“two different polypeptides. A and B, with a molecular mass of 42 and 40 kDa, respectively”
Claim · model-written summary
GS subunit A was present in ungerminated scutellum and remained unchanged during germination.
Not reportedTaxon
Verbatim
e0“In the scutellum subunit A was already present in the ungerminated seed and remained unchanged”
Claim · model-written summary
GS subunit B appeared on day 2 and increased about fivefold during scutellum germination.
Not reportedTaxon
Verbatim
e0“subunit B appeared on day 2 and increased about 5-fold during germination”
Claim · model-written summary
GS polypeptide B appeared later in aleurone, roots, and weakly in shoots.
Not reportedTaxon
Verbatim
e0“Polypeptide B also appeared later during germination in the aleurone layer, roots and weakly in the etiolated shoots”
Claim · model-written summary
GS was detected in scutellum and aleurone during germination.
- Taxon
- barley
.jpg?width=60)
Hordeum vulgaree0 - Organ / stage
- scutellum and the aleurone layere0
- Outcome
- GSe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“GS was detected in the scutellum and the aleurone layer of barley seeds during germination”
Claim · model-written summary
The scutellum contained a cytosolic GS isozyme.
Not reportedTaxon
Verbatim
e0“a cytosolic isozyme was present in the scutellum”
Claim · model-written summary
Only cytosolic GS was expressed in barley seed, with subunit composition changing during germination.
- Taxon
- barleyHordeum vulgaree0
- Outcome
- cytosolic GSe0
- Direction
- changese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“only a cytosolic GS is expressed in barley seed, and its subunit composition changes during germination”