Open Access Research article

Integration Host Factor (IHF) binds to the promoter region of the phtD operon involved in phaseolotoxin synthesis in P. syringae pv. phaseolicola NPS3121

Jackeline Lizzeta Arvizu-Gómez1, Alejandro Hernández-Morales1, Guillermo Pastor-Palacios2, Luis G Brieba2 and Ariel Álvarez-Morales1*

Author Affiliations

1 Departamento de Ingeniería Genética, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional Unidad Irapuato, Apdo Postal 629, CP 36821, Irapuato, Gto, México

2 Laboratorio Nacional de Genómica para la Biodiversidad, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apdo Postal 629, CP 36821, Irapuato, Gto, México

For all author emails, please log on.

BMC Microbiology 2011, 11:90  doi:10.1186/1471-2180-11-90

Published: 4 May 2011

Abstract

Background

Pseudomonas syringae pv. phaseolicola, the causal agent of halo blight disease in beans, produces a toxin known as phaseolotoxin, in whose synthesis participate a group of genes organized within the genome in a region known as the "Pht cluster". This region, which is thought to have been acquired by horizontal gene transfer, includes 5 transcriptional units, two monocistronic (argK, phtL) and three polycistronic (phtA, phtD, phtM), whose expression is temperature dependent. So far, the regulatory mechanisms involved in phaseolotoxin synthesis have not been elucidated and the only well-established fact is the requirement of low temperatures for its synthesis. In this work, we searched for regulatory proteins that could be involved in phaseolotoxin synthesis, focusing on the regulation of the phtD operon.

Results

In this study we identified the global regulator IHF (Integration Host Factor), which binds to the promoter region of the phtD operon, exerting a negative effect on the expression of this operon. This is the first regulatory protein identified as part of the phaseolotoxin synthesis system. Our findings suggest that the Pht cluster was similarly regulated in the ancestral cluster by IHF or similar protein, and integrated into the global regulatory mechanism of P. syringae pv. phaseolicola, after the horizontal gene transfer event by using the host IHF protein.

Conclusion

This study identifies the IHF protein as one element involved in the regulation of phaseolotoxin synthesis in P. syringae pv. phaseolicola NPS3121 and provides new insights into the regulatory mechanisms involved in phaseolotoxin production.