Hydrogen sulfide causes excision of a genomic island in Pseudomonas syringae pv. phaseolicola
European Journal of Plant Pathology
© The Author(s) 2017. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.
Hydrogen sulfide (H 2 S) is known to be an important signalling molecule in both animals and plants, despite its toxic nature. In plants it has been seen to control stomatal apertures, so altering the ability of bacteria to invade plant tissues. Bacteria are known to generate H 2 S as well as being exposed to plant-generated H 2 S. During their interaction with plants pathogenic bacteria are known to undergo alterations to their genomic complement. For example Pseudomonas syringae pv. phaseolicola (Pph) strain 1302A undergoes loss of a section of DNA known as a genomic island (PPHGI-1) when exposed to the plants resistance response. Loss of PPHGI-1 from Pph 1302A enables the pathogen to overcome the plants resistance response and cause disease. Here, with the use of H 2 S donor molecules, changes induced in Pph 1302A genome, as demonstrated by excision of PPHGI-1, were investigated. Pph 1302A cells were found to be resistant to low concentrations of H 2 S. However, at sub-lethal H 2 S concentrations an increase in the expression of the PPHGI-1 encoded integrase gene (xerC), which is responsible for island excision, and a subsequent increase in the presence of the circular form of PPHGI-1 were detected. This suggests that H 2 S is able to initiate excision of PPHGI-1 from the Pph genome. Therefore, H 2 S that may emanate from the plant has an effect on the genome structure of invading bacteria and their ability to cause disease in plants. Modulation of such plant signals may be a way to increase plant defence responses for crops in the future.
We would like to thank the University of the West of England, Bristol for financial support for this work.
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Vol. 149 (4), pp. 911 - 921