The Rhizobium GstI protein reduces the NH4+ assimilation capacity of Rhizobium leguminosarum

We show that the protein encoded by the glutamine synthetase translational inhibitor (gstI) gene reduces the NH4+ assimilation capacity of Rhizobium leguminosarum. In this organism, gstI expression is regulated by the ntr system, including the PII protein, as a function of the nitrogen (N) status of...

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Published in:	Molecular plant-microbe interactions Vol. 14; no. 7; pp. 823 - 831
Main Authors:	TATS, Rosarita, MANDRICH, Luigl, SPINOSA, Maria R, RICCIO, Anna, LAMBERTI, Alessandro, LACCARINO, Maurizio, PATRIARCA, Eduardo J
Format:	Journal Article
Language:	English
Published:	St Paul, MN APS Press 01-07-2001 The American Phytopathological Society
Subjects:	Agronomy. Soil science and plant productions Bacterial Proteins - genetics Bacterial Proteins - metabolism Base Sequence Biological and medical sciences DNA, Bacterial - genetics Economic plant physiology Fabaceae - microbiology Fundamental and applied biological sciences. Psychology Genes, Bacterial Glutamate-Ammonia Ligase - metabolism histochemical localization Mutagenesis, Site-Directed Mutation Nitrogen - metabolism Nitrogen Fixation - genetics Parasitism and symbiosis PCR mutagenesis Plant physiology and development posttranscriptional regulation Promoter Regions, Genetic protein purification Quaternary Ammonium Compounds - metabolism Repressor Proteins - genetics Repressor Proteins - metabolism Rhizobium leguminosarum - genetics Rhizobium leguminosarum - growth & development Rhizobium leguminosarum - metabolism Symbiosis Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...) Vicia hirsuta Symbiosis Symbionte Ammonium Symbiotic relation Nutrition Plant nodule Translation inhibitor Gene expression Metabolism Inorganic element Structure function relationship Rhizobium leguminosarum Endocytosis Regulation(control) Leguminosae Dicotyledones Angiospermae Nitrogen fixation Bacteria Nutrient Spermatophyta Rhizobiaceae Cytoplasm
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Summary:	We show that the protein encoded by the glutamine synthetase translational inhibitor (gstI) gene reduces the NH4+ assimilation capacity of Rhizobium leguminosarum. In this organism, gstI expression is regulated by the ntr system, including the PII protein, as a function of the nitrogen (N) status of the cells. The GstI protein, when expressed from an inducible promoter, inhibits glutamine synthetase II (glnII) expression under all N conditions tested. The induction of gstI affects the growth of a glutamine synthetase I (glnA-) strain and a single amino acid substitution (W48D) results in the complete loss of GstI function. During symbiosis, gstI is expressed in young differentiating symbiosomes (SBs) but not in differentiated N2-fixing SBs. In young SBs, the PII protein modulates the transcription of NtrC-regulated genes such as gstI and glnII. The evidence presented herein strengthens the idea that the endocytosis of bacteria inside the cytoplasm of the host cells is a key step in the regulation of NH4+ metabolism.
ISSN:	0894-0282 1943-7706
DOI:	10.1094/MPMI.2001.14.7.823