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ARS Home » Pacific West Area » Corvallis, Oregon » Horticultural Crops Research Unit » Research » Publications at this Location » Publication #320440
Title: Phloroglucinol functions as an intracellular and intercellular chemical messenger influencing gene expression in Pseudomonas protegens

Author
item Clifford, Jennifer
item BUCHANAN, ALEX - Oregon State University
item VINING, OLIVER - Oregon State University
item Kidarsa, Teresa
item CHANG, JEFF - Oregon State University
item MCPHAIL, KERRY - Oregon State University
item Loper, Joyce

Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2015
Publication Date: 10/14/2015
Citation: Clifford, J.M., Buchanan, A., Vining, O., Kidarsa, T.A., Chang, J.H., Mcphail, K., Loper, J.E. 2015. Phloroglucinol functions as an intracellular and intercellular chemical messenger influencing gene expression in Pseudomonas protegens. Environmental Microbiology. 18(10):3296-3308. doi: 10.1111/1462-2920.13043.

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 spp., which is a genus of bacteria that occurs naturally on plant surfaces such as leaves and roots. In this study, we identified a chemical compound that controls the production of antifungal compounds by the biological control bacterium Pseudomonas protegens Pf-5. We show that this compound controls the expression of many genes, including those involved in biological control. These results are important to other scientists because the broad role of this compound was unexpected, so the research advances knowledge of bacterial gene regulation. The results also add to the information about factors influencing gene expression in plant-associated Pseudomonas spp., which can assist scientists in formulated more consistent biological control strategies for use in agriculture.

Technical Abstract: Bacteria can be both highly communicative and highly competitive in natural habitats and antibiotics are thought to play a role in both of these processes. The soil bacterium Pseudomonas protegens Pf-5 produces a spectrum of antibiotics, two of which, pyoluteorin and 2,4-diacetylphloroglucinol (DAPG), function in intracellular and intercellular communication, both as autoinducers of their own production. Here, we demonstrate that phloroglucinol (PG), an intermediate in DAPG biosynthesis, can serve as an intercellular signal influencing the expression of pyoluteorin biosynthesis genes, the production of pyoluteorin, and inhibition of Pythium ultimum, a phytopathogenic oomycete sensitive to pyoluteorin. Through analysis of RNAseq data sets, we show that phloroglucinol had broad effects on the transcriptome of Pf-5, significantly altering the transcription of more than a hundred genes by at least two fold. The effects of nanomolar versus micromolar concentrations of phloroglucinol differed both quantitatively and qualitatively, influencing the expression of distinct sets of genes or having opposite effects on transcript abundance of certain genes. Therefore, our results support the concept of hormesis, a phenomenon associated with signaling molecules that elicit distinct responses at different concentrations.