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The 5' untranslated region of the soybean cytosolic glutamine synthetase ?(1) gene contains prokaryotic translation initiation signals and acts as a translational enhancer in plants.

ABSTRACT: Glutamine synthetase (GS) catalyzes the synthesis of glutamine from glutamate and ammonia. In plants, it occurs as two major isoforms, a cytosolic form (GS(1)) and a nuclear encoded chloroplastic form. The focus of this paper is to determine the role of the 5'UTR of a GS(1) gene. GS(1) gene constructs with and without its 5' and 3' UTRs, driven by a constitutive promoter, were agroinfiltrated into tobacco leaves and the tissues were analyzed for both transgene transcript and protein accumulation. The constructs were also tested in an in vitro transcription/translation system and in Escherichia coli. Our results showed that while the 3'UTR functioned in the destabilization of the transcript, the 5'UTR acted as a translation enhancer in plant cells but not in the in vitro translation system. The 5'UTR of the GS(1) gene when placed in front of a reporter gene (uidA), showed a 20-fold increase in the level of GUS expression in agroinfiltrated leaves when compared to the same gene construct without the 5'UTR. The 5'UTR-mediated translational enhancement is probably another step in the regulation of GS in plants. The presence of the GS(1) 5'UTR in front of the GS(1) coding region allowed for its translation in E. coli suggesting the commonality of the translation initiation mechanism for this gene between plants and bacteria.

SUBMITTER: Ortega JL

PROVIDER: S-EPMC3881598 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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The 5' untranslated region of the soybean cytosolic glutamine synthetase β(1) gene contains prokaryotic translation initiation signals and acts as a translational enhancer in plants.

Ortega Jose Luis JL Wilson Olivia L OL Sengupta-Gopalan Champa C

Molecular genetics and genomics : MGG 20121019 11-12

Glutamine synthetase (GS) catalyzes the synthesis of glutamine from glutamate and ammonia. In plants, it occurs as two major isoforms, a cytosolic form (GS(1)) and a nuclear encoded chloroplastic form. The focus of this paper is to determine the role of the 5'UTR of a GS(1) gene. GS(1) gene constructs with and without its 5' and 3' UTRs, driven by a constitutive promoter, were agroinfiltrated into tobacco leaves and the tissues were analyzed for both transgene transcript and protein accumulation ...[more]

PMID: 23080263

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Project description:BackgroundNitrogen is a crucial nutrient that is both essential and rate limiting for plant growth and seed production. Glutamine synthetase (GS), occupies a central position in nitrogen assimilation and recycling, justifying the extensive number of studies that have been dedicated to this enzyme from several plant sources. All plants species studied to date have been reported as containing a single, nuclear gene encoding a plastid located GS isoenzyme per haploid genome. This study reports the existence of a second nuclear gene encoding a plastid located GS in Medicago truncatula.ResultsThis study characterizes a new, second gene encoding a plastid located glutamine synthetase (GS2) in M. truncatula. The gene encodes a functional GS isoenzyme with unique kinetic properties, which is exclusively expressed in developing seeds. Based on molecular data and the assumption of a molecular clock, it is estimated that the gene arose from a duplication event that occurred about 10 My ago, after legume speciation and that duplicated sequences are also present in closely related species of the Vicioide subclade. Expression analysis by RT-PCR and western blot indicate that the gene is exclusively expressed in developing seeds and its expression is related to seed filling, suggesting a specific function of the enzyme associated to legume seed metabolism. Interestingly, the gene was found to be subjected to alternative splicing over the first intron, leading to the formation of two transcripts with similar open reading frames but varying 5' UTR lengths, due to retention of the first intron. To our knowledge, this is the first report of alternative splicing on a plant GS gene.ConclusionsThis study shows that Medicago truncatula contains an additional GS gene encoding a plastid located isoenzyme, which is functional and exclusively expressed during seed development. Legumes produce protein-rich seeds requiring high amounts of nitrogen, we postulate that this gene duplication represents a functional innovation of plastid located GS related to storage protein accumulation exclusive to legume seed metabolism.

Dataset Information

The 5' untranslated region of the soybean cytosolic glutamine synthetase ?(1) gene contains prokaryotic translation initiation signals and acts as a translational enhancer in plants.

Publications

The 5' untranslated region of the soybean cytosolic glutamine synthetase β(1) gene contains prokaryotic translation initiation signals and acts as a translational enhancer in plants.

Similar Datasets

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