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Title: PcsR2 Is a LuxR-Type Regulator That Is Upregulated on Wheat Roots and Is Unique to Pseudomonas chlororaphis

Abstract

LuxR solos are common in plant-associated bacteria and increasingly recognized for playing important roles in plant-microbe interkingdom signaling. Unlike the LuxR-type transcriptional regulators of prototype LuxR/LuxI quorum sensing systems, luxR solos do not have a LuxI-type autoinducer synthase gene associated with them. LuxR solos in plant-pathogenic bacteria are important for virulence and in plant endosymbionts contribute to symbiosis. In the present study, we characterized an atypical LuxR solo, PcsR2, in the biological control species Pseudomonas chlororaphis 30–84 that is highly conserved among sequenced P. chlororaphis strains. Unlike most LuxR solos in the plant-associated bacteria characterized to date, pcsR2 is not associated with a proline iminopeptidase gene and the protein has an atypical N-terminal binding domain. We created a pcsR2 deletion mutant and used quantitative RT-PCR to show that the expression of pcsR2 and genes in the operon immediately downstream was upregulated ~10-fold when the wild type strain was grown on wheat roots compared to planktonic culture. PcsR2 was involved in upregulation. Using a GFP transcriptional reporter, we found that expression of pcsR2 responded specifically to root-derived substrates as compared to leaf-derived substrates but not to endogenous AHLs. Compared to the wild type, the mutant was impaired in the ability tomore » utilize root carbon and nitrogen sources in wheat root macerate and to colonize wheat roots. Phenazine production and most biofilm traits previously shown to be correlated with phenazine production also were diminished in the mutant. Gene expression of several of the proteins in the phenazine regulatory network including PhzR, Pip (phenazine inducing protein) and RpeA/RpeB were reduced in the mutant, and overexpression of these genes in trans restored phenazine production in the mutant to wild-type levels, indicating PcsR2 affects the activity of the these regulatory genes upstream of RpeA/RpeB via an undetermined mechanism. Our results indicate PcsR2 upregulates the expression of the adjacent operon in response to unknown wheat root-derived signals and belongs to a novel subfamily of LuxR-type transcriptional regulators found in sequenced P. chlororaphis strains.« less

Authors:
 [1];  [2];  [3]
  1. Texas A & M Univ., College Station, TX (United States). Molecular and Environmental Plant Sciences Program and Dept. of Horticulture Sciences
  2. Texas A & M Univ., College Station, TX (United States). Dept. of Plant Pathology and Microbiology
  3. Texas A & M Univ., College Station, TX (United States). Molecular and Environmental Plant Sciences Program, Dept. of Plant Pathology and Microbiology, and Dept. of Horticulture Sciences
Publication Date:
Research Org.:
Texas A & M Univ., College Station, TX (United States). Texas A & M AgriLife Research
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1848487
Grant/Contract Number:  
EE0007104
Resource Type:
Accepted Manuscript
Journal Name:
Frontiers in Microbiology
Additional Journal Information:
Journal Volume: 11; Journal ID: ISSN 1664-302X
Publisher:
Frontiers Research Foundation
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; microbiology; plant-microbe interactions; interkingdom signaling; LuxR solos; Pseudomonas; phenazine

Citation Formats

Pan, Huiqiao, Pierson, Leland S., and Pierson, Elizabeth A. PcsR2 Is a LuxR-Type Regulator That Is Upregulated on Wheat Roots and Is Unique to Pseudomonas chlororaphis. United States: N. p., 2020. Web. doi:10.3389/fmicb.2020.560124.
Pan, Huiqiao, Pierson, Leland S., & Pierson, Elizabeth A. PcsR2 Is a LuxR-Type Regulator That Is Upregulated on Wheat Roots and Is Unique to Pseudomonas chlororaphis. United States. https://doi.org/10.3389/fmicb.2020.560124
Pan, Huiqiao, Pierson, Leland S., and Pierson, Elizabeth A. Tue . "PcsR2 Is a LuxR-Type Regulator That Is Upregulated on Wheat Roots and Is Unique to Pseudomonas chlororaphis". United States. https://doi.org/10.3389/fmicb.2020.560124. https://www.osti.gov/servlets/purl/1848487.
@article{osti_1848487,
title = {PcsR2 Is a LuxR-Type Regulator That Is Upregulated on Wheat Roots and Is Unique to Pseudomonas chlororaphis},
author = {Pan, Huiqiao and Pierson, Leland S. and Pierson, Elizabeth A.},
abstractNote = {LuxR solos are common in plant-associated bacteria and increasingly recognized for playing important roles in plant-microbe interkingdom signaling. Unlike the LuxR-type transcriptional regulators of prototype LuxR/LuxI quorum sensing systems, luxR solos do not have a LuxI-type autoinducer synthase gene associated with them. LuxR solos in plant-pathogenic bacteria are important for virulence and in plant endosymbionts contribute to symbiosis. In the present study, we characterized an atypical LuxR solo, PcsR2, in the biological control species Pseudomonas chlororaphis 30–84 that is highly conserved among sequenced P. chlororaphis strains. Unlike most LuxR solos in the plant-associated bacteria characterized to date, pcsR2 is not associated with a proline iminopeptidase gene and the protein has an atypical N-terminal binding domain. We created a pcsR2 deletion mutant and used quantitative RT-PCR to show that the expression of pcsR2 and genes in the operon immediately downstream was upregulated ~10-fold when the wild type strain was grown on wheat roots compared to planktonic culture. PcsR2 was involved in upregulation. Using a GFP transcriptional reporter, we found that expression of pcsR2 responded specifically to root-derived substrates as compared to leaf-derived substrates but not to endogenous AHLs. Compared to the wild type, the mutant was impaired in the ability to utilize root carbon and nitrogen sources in wheat root macerate and to colonize wheat roots. Phenazine production and most biofilm traits previously shown to be correlated with phenazine production also were diminished in the mutant. Gene expression of several of the proteins in the phenazine regulatory network including PhzR, Pip (phenazine inducing protein) and RpeA/RpeB were reduced in the mutant, and overexpression of these genes in trans restored phenazine production in the mutant to wild-type levels, indicating PcsR2 affects the activity of the these regulatory genes upstream of RpeA/RpeB via an undetermined mechanism. Our results indicate PcsR2 upregulates the expression of the adjacent operon in response to unknown wheat root-derived signals and belongs to a novel subfamily of LuxR-type transcriptional regulators found in sequenced P. chlororaphis strains.},
doi = {10.3389/fmicb.2020.560124},
journal = {Frontiers in Microbiology},
number = ,
volume = 11,
place = {United States},
year = {Tue Nov 10 00:00:00 EST 2020},
month = {Tue Nov 10 00:00:00 EST 2020}
}

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