期刊
MOLECULAR MICROBIOLOGY
卷 62, 期 3, 页码 760-771出版社
WILEY
DOI: 10.1111/j.1365-2958.2006.05400.x
关键词
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资金
- NIAID NIH HHS [T32 AI007414] Funding Source: Medline
- NIGMS NIH HHS [GM59776] Funding Source: Medline
The bacterial mutualist Xenorhabdus nematophila colonizes a specific region of its nematode host Steinernema carpocapsae. We previously reported the identification of a chromosomal locus encoding three X. nematophila genes of unknown function, nilA, B and C, that are each necessary for colonization. Subsequent work indicated the global regulator Lrp is a repressor of nilC: nilC transcription is elevated in an lrp mutant and Lrp interacts directly with the nilC promoter. In this manuscript, we report the identification of an additional gene, nilR, required for repression of nilC transcription. We show that nilR and lrp mutants also have elevated expression of nilA and nilB, demonstrating that nilA, B and C are co-ordinately regulated. nil gene expression is derepressed most strongly when both nilR and lrp are lacking, suggesting NilR and Lrp synergistically repress nil transcription. NilR contains a helix-turn-helix-type DNA binding domain and likely acts directly at promoters. A comparison of the wild type and nilR proteomes indicates that NilR, unlike Lrp, regulates a small number of genes. Finally, X. nematophila carrying an ectopic copy of nilR colonizes at similar to 60-fold lower levels than the control strain, suggesting that derepression of nil gene expression is necessary for nematode colonization.
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