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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #331767
Title: Disruption of transporters affiliated with enantio-pyochelin biosynthesis gene cluster of Pseudomonas protegens Pf-5 has pleiotropic effects

Author
item LIM, CHEE - Macquarie University
item PENESYAN, ANAHIT - Macquarie University
item HASSAN, KARL - Macquarie University
item LOPER, JOYCE - Former ARS Employee
item PAULSEN, IAN - Macquarie University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2016
Publication Date: 7/21/2016
Citation: Lim, C.K., Penesyan, A., Hassan, K.A., Loper, J.E., Paulsen, I.T. 2016. Disruption of transporters affiliated with enantio-pyochelin biosynthesis gene cluster of Pseudomonas protegens Pf-5 has pleiotropic effects. PLoS One. 11(7):e0159884. doi: 10.1371/journal.pone.0159884.

Interpretive Summary: Biological control provides a promising strategy for managing plant diseases, but has not yet been utilized widely in agriculture due, in part, to unexplained variation in its success in managing disease. Our research goals are to identify sources of variation in biological control, and devise ways to make it more reliable. We focus on Pseudomonas bacteria that occur naturally on plant surfaces such as leaves and roots. Specifically, we focus on Pseudomonas protegens strain Pf-5, which lives on plant seeds and roots, and protects the plant from infection by plant pathogens that live in the soil. Iron is a prevalent element in the soil, but it is in a form that is unavailable to bacteria like Pf-5. In this study, we investigated the function of genes in a gene cluster for production of an iron-chelating compound (siderophore) called enantio-pyochelin. This compound is secreted by cells of Pf-5, chelates iron in the environment, and is then transported back into the cell to provide iron for bacterial growth. In this study, we found that the membrane transporters encoded by genes in the enantio-pyochelin cluster have diverse functions in the uptake of resources and stress response of Pf-5. These data fit into an emerging picture of environmental factors influencing this biological control bacterium.

Technical Abstract: Pseudomonas protegens Pf-5 (formerly Pseudomonas fluorescens) is a biocontrol bacterium that produces the siderophore enantio-pyochelin under conditions of iron starvation in a process that is often accompanied by the secretion of its biosynthesis intermediates, salicylic acid and dihydroaeruginoic acid. In this study, we investigated whether several transporters that are encoded by genes within or adjacent to the enantio-pyochelin biosynthetic cluster, serve as efflux systems for enantio-pyochelin and/or its intermediates. In addition, we determined whether these transporters have broad substrates range specificity using a Phenotype Microarray system. Intriguingly, knockouts of the pchH and fetF transporter genes resulted in mutant strains that secrete higher levels of enantio-pyochelin as well as its intermediates salicylic acid and dihydroaeruginoic acid. Analyses of these mutants did not indicate significant change in transcription of biosynthetic genes involved in enantiopyochelin production. In contrast, the deletion mutant of PFL_3504 resulted in reduced transcription of the biosynthetic genes as well as decreased dihydroaeruginoic acid concentrations in the culture supernatant, which could either point to regulation of gene expression by the transporter or its role in dihydroaeruginoic acid transport. Disruption of each of the transporters resulted in altered stress and/or chemical resistance profile of Pf-5, which may reflect that these transporters could have specificity for rather a broad range of substrates.