Location: Horticultural Crops ResearchTitle: Identification of a Signal That Mediates the Crosstalk Between Biosynthetic Gene Clusters for the Antibiotics 2,4-diacetylphloroglucinol and Pyoluteorin in Pseudomonas protegens Pf-5 Author
|Yan, Qing - Oregon State University|
|Philmus, Benjamin - Oregon State University|
|Chang, Jeff - Oregon State University|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2015
Publication Date: 9/8/2015
Citation: Yan, Q., Philmus, B., Chang, J.H., Loper, J.E. 2015. Identification of a Signal That Mediates the Crosstalk Between Biosynthetic Gene Clusters for the Antibiotics 2,4-diacetylphloroglucinol and Pyoluteorin in Pseudomonas protegens Pf-5 [abstract]. American Society for Microbiology Conference on Pseudomonas 2015.
Technical Abstract: Pseudomonas protegens Pf-5 produces a broad spectrum of secondary metabolites with anti-microbial activity. The production of two of these metabolites, 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin, is coordinately regulated. Our previous study indicated that phloroglucinol, an intermediate in the synthesis of DAPG, is required for the production of pyoluteorin and can regulate the transcription of pyoluteorin biosynthetic genes in a concentration-dependent manner. However, the mechanism by which phloroglucinol regulates pyoluteorin production remains obscure. Here we report that phloroglucinol-mediated regulation of the pyoluteorin biosynthesis gene pltA by the linked transcriptional regulator PltR was abolished by a mutation in pltM, which encodes a putative halogenase. A pltM mutant of Pf-5 could not produce pyoluteorin or express pltA, even in the presence of phloroglucinol. The role of pltM in the pyoluteorin biosynthesis is intriguing because the biosynthesis gene cluster contains two halogenase-encoding genes, pltA and pltM, and PltA is sufficient to add both chlorines to pyoluteorin. Further investigations indicated that the expression of pltA in the pltM mutant could be activated by the supernatant of wild-type Pf-5 cultures. With these data, we hypothesized that pltM synthesizes a signal from phloroglucinol. We purified PltM and found that the purified protein could convert phloroglucinol into new compounds in vitro. These compounds induced pltA expression in a pltM deficient strain. The chemical structures of the compounds were elucidated by LC-MS as 2-chloro-1,3,5-trihydroxybenzene and 2,4-dichlorobenzene-1,3,5-triol, two chlorinated derivatives of phloroglucinol. Taken together, our data suggest that phloroglucinol was processed by PltM into two chlorinated phloroglucinol derivatives, which function as intercellular signals regulating pyoluteorin gene expression. To our knowledge, this is the first example of co-regulation of two antibiotics mediated by transforming an intermediate of one pathway into signals activating the second pathway.