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Journal of Bacteriology, February 2009, p. 890-897, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01507-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

OryR Is a LuxR-Family Protein Involved in Interkingdom Signaling between Pathogenic Xanthomonas oryzae pv. oryzae and Rice {triangledown}

Sara Ferluga1 and Vittorio Venturi1,2*

Bacteriology Group, International Centre for Genetic Engineering & Biotechnology, Trieste, Italy,1 Plant Bacteriology Group, International Centre for Genetic Engineering & Biotechnology, Biosafety Outstation, Ca'Tron, Treviso, Italy2

Received 25 October 2008/ Accepted 17 November 2008

Xanthomonas oryzae pv. oryzae, the causal agent of bacterial leaf blight in rice, contains a regulator that is encoded in the genome, designated OryR, which belongs to the N-acyl homoserine lactone (AHL)-dependent quorum-sensing LuxR subfamily of proteins. However, we previously reported that X. oryzae pv. oryzae does not make AHLs and does not possess a LuxI-family AHL synthase and that the OryR protein is solubilized by a compound present in rice. In this study we obtained further evidence that OryR interacts with a rice signal molecule (RSM) and that the OryR concentration increases when rice is infected with X. oryzae pv. oryzae. We also describe three OryR target promoters which are regulated differently: (i) the neighboring proline iminopeptidase (pip) virulence gene, which is positively regulated by OryR in the presence of the RSM; (ii) the oryR promoter, which is negatively autoregulated independent of the RSM; and (iii) the 1,4-β-cellobiosidase cbsA gene, which is positively regulated by OryR independent of the RSM. We also found that the RSM for OryR is small, is not related to AHLs, and is not able to activate the broad-range AHL biosensor Agrobacterium tumefaciens NT1(pZLQR). Furthermore, OryR does not regulate production of the quorum-sensing diffusible signal factor present in the genus Xanthomonas. Therefore, OryR has unique features and is an important regulator involved in interkingdom communication between the host and the pathogen.

* Corresponding author. Mailing address: Bacteriology Group, International Center for Genetic Engineering & Biotechnology, Padriciano 99, 34012 Trieste, Italy. Phone: 390403757319. Fax: 39040226555. E-mail: venturi{at}icgeb.org

{triangledown} Published ahead of print on 21 November 2008.

Journal of Bacteriology, February 2009, p. 890-897, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01507-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Subramoni, S., Venturi, V. (2009). LuxR-family 'solos': bachelor sensors/regulators of signalling molecules. Microbiology 155: 1377-1385 [Abstract] [Full Text]  
  • Malott, R. J., O'Grady, E. P., Toller, J., Inhulsen, S., Eberl, L., Sokol, P. A. (2009). A Burkholderia cenocepacia Orphan LuxR Homolog Is Involved in Quorum-Sensing Regulation. J. Bacteriol. 191: 2447-2460 [Abstract] [Full Text]  


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