Global gene expression during stringent response in Corynebacterium glutamicum in presence and absence of the rel gene encoding pppGpp synthaseReport as inadecuate




Global gene expression during stringent response in Corynebacterium glutamicum in presence and absence of the rel gene encoding pppGpp synthase - Download this document for free, or read online. Document in PDF available to download.

BMC Genomics

, 7:230

First Online: 08 September 2006Received: 04 July 2006Accepted: 08 September 2006

Abstract

BackgroundThe stringent response is the initial reaction of microorganisms to nutritional stress. During stringent response the small nucleotides pppGpp act as global regulators and reprogram bacterial transcription. In this work, the genetic network controlled by the stringent response was characterized in the amino acid-producing Corynebacterium glutamicum.

ResultsThe transcriptome of a C. glutamicum rel gene deletion mutant, unable to synthesize pppGpp and to induce the stringent response, was compared with that of its rel-proficient parent strain by microarray analysis. A total of 357 genes were found to be transcribed differentially in the rel-deficient mutant strain. In a second experiment, the stringent response was induced by addition of DL-serine hydroxamate SHX in early exponential growth phase. The time point of the maximal effect on transcription was determined by real-time RT-PCR using the histidine and serine biosynthetic genes. Transcription of all of these genes reached a maximum at 10 minutes after SHX addition. Microarray experiments were performed comparing the transcriptomes of SHX-induced cultures of the rel-proficient strain and the rel mutant. The differentially expressed genes were grouped into three classes. Class A comprises genes which are differentially regulated only in the presence of an intact rel gene. This class includes the non-essential sigma factor gene sigB which was upregulated and a large number of genes involved in nitrogen metabolism which were downregulated. Class B comprises genes which were differentially regulated in response to SHX in both strains, independent of the rel gene. A large number of genes encoding ribosomal proteins fall into this class, all being downregulated. Class C comprises genes which were differentially regulated in response to SHX only in the rel mutant. This class includes genes encoding putative stress proteins and global transcriptional regulators that might be responsible for the complex transcriptional patterns detected in the rel mutant when compared directly with its rel-proficient parent strain.

ConclusionIn C. glutamicum the stringent response enfolds a fast answer to an induced amino acid starvation on the transcriptome level. It also showed some significant differences to the transcriptional reactions occuring in Escherichia coli and Bacillus subtilis. Notable are the rel-dependent regulation of the nitrogen metabolism genes and the rel-independent regulation of the genes encoding ribosomal proteins.

Electronic supplementary materialThe online version of this article doi:10.1186-1471-2164-7-230 contains supplementary material, which is available to authorized users.

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Author: Olaf Brockmann-Gretza - Jörn Kalinowski

Source: https://link.springer.com/article/10.1186/1471-2164-7-230







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