Transcriptome analysis of the role of GlnD/GlnBK in nitrogen stress adaptation by Sinorhizobium meliloti Rm1021.

Svetlana N Yurgel,Jennifer Rice,Michael L Kahn

doi:10.1371/journal.pone.0058028

Svetlana N Yurgel, Jennifer Rice + Show 1 more

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https://doi.org/10.1371/journal.pone.0058028

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Journal: PloS one	Publication Date: Mar 13, 2013
Citations: 64	License type: CC BY 4.0

Affiliation: Washington State University

Abstract

Transcriptional changes in the nitrogen stress response (NSR) of wild type S. meliloti Rm1021, and isogenic strains missing both PII proteins, GlnB and GlnK, or carrying a ΔglnD-sm2 mutation were analyzed using whole-genome microarrays. This approach allowed us to identify a number of new genes involved in the NSR and showed that the response of these bacteria to nitrogen stress overlaps with other stress responses, including induction of the fixK2 transcriptional activator and genes that are part of the phosphate stress response. Our data also show that GlnD and GlnBK proteins may regulate many genes that are not part of the NSR. Analysis of transcriptome profiles of the Rm1021 ΔglnD-sm2 strain allowed us to identify several genes that appear to be regulated by GlnD without the participation of the PII proteins.

Highlights

Nitrogen is an essential chemical element for all living organisms
We showed the presence of these two nitrogen sources in growth media significantly affected the expression level of GSII and modification state of GSI [11] in S. meliloti Rm1021 and we concluded that these media were suitable for creating nitrogen limited (Glu) and nitrogen sufficient (NH4) growth conditions
To test whether glnD deletion affected EPS I production we evaluated the ability of Rm1021, Rm1021DglnD-sm2 and Rm1021DglnBDglnK to produce high molecular weight (HMW) EPS I under high and low nitrogen availability

Summary

Introduction

Nitrogen is an essential chemical element for all living organisms. It is an irreplaceable component of proteins, DNA and RNA – the building blocks in every living cell on Earth. Because of the inert nature of N2, nitrogen availability is a major factor limiting plant and bacterial development. The bacterial Nitrogen Stress Response (NSR) regulatory cascade is well defined, especially in enteric bacteria [1,2]. The uridylyltransferase and uridylyl cleavage enzyme GlnD is a primary sensor that activates the NSR in nitrogen-limited cells by uridylylating PII proteins (usually GlnB and GlnK). The activity of a two component regulatory system, NtrBC, is controlled by PII protein modification, resulting in NtrC phosphorylation and activation of nitrogen catabolism and assimilation under nitrogen limitation [2]. In E. coli, communication between GlnD and the NSR is mediated by the PII proteins; in a mutant lacking both GlnB and GlnK, the NSR phenotype does not depend on presence of GlnD [3]

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