Abstract

Pantoea ananatis LMG 2665T synthesizes and utilizes acyl homoserine lactones (AHLs) for signalling. The complete set of genes regulated by the EanI/R quorum sensing (QS) system in this strain is still not fully known. In this study, RNA-sequencing (RNA-seq) was used to identify the EanI/R regulon in LMG 2665T. Pairwise comparisons of LMG 2665T in the absence of AHLs (Optical density (OD)600 = 0.2) and in the presence of AHLs (OD600 = 0.5) were performed. Additionally, pairwise comparisons of LMG 2665T and its QS mutant at OD600 = 0.5 were undertaken. In total, 608 genes were differentially expressed between LMG 2665T at OD600 = 0.5 versus the same strain at OD600 = 0.2 and 701 genes were differentially expressed between LMG 2665T versus its QS mutant at OD600 = 0.5. A total of 196 genes were commonly differentially expressed between the two approaches. These constituted approximately 4.5% of the whole transcriptome under the experimental conditions used in this study. The RNA-seq data was validated by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR). Genes found to be regulated by EanI/R QS were those coding for redox sensing, metabolism, flagella formation, flagella dependent motility, cell adhesion, biofilm formation, regulators, transport, chemotaxis, methyl accepting proteins, membrane proteins, cell wall synthesis, stress response and a large number of hypothetical proteins. The results of this study give insight into the genes that are regulated by the EanI/R system in LMG 2665T. Functional characterization of the QS regulated genes in LMG 2665T could assist in the formulation of control strategies for this plant pathogen.

Highlights

  • Pantoea ananatis is an ubiquitous, Gram-negative, yellow pigmented, rod shaped bacterium that has been described as an “emerging pathogen” of global importance [1]

  • The bacterial strains used in this study are P. ananatis LMG 2665T (virulent natural isolate from pineapple obtained from Belgian co-ordinated collections of microorganisms (BCCM)/LMG, University of Gent, Gent, Belgium), LMG 2665T ean∆I/R (P. ananatis LMG 2665T ∆ resistant to kanamycin) [5], Chromobacterium violaceum 026

  • The sampling points were determined by detection of acyl homoserine lactones (AHLs) using the CV026 assay as described

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Summary

Introduction

Pantoea ananatis is an ubiquitous, Gram-negative, yellow pigmented, rod shaped bacterium that has been described as an “emerging pathogen” of global importance [1]. This bacterium infects plants and is capable of surviving in different environments [1]. This pathogen causes disease symptoms in a number of economically important plants such as Eucalyptus [1,2], staple food crops, namely maize, rice and sorghum [3] as well as cash crops, for example, honeydew melons, pineapples and onions [1]. Unlike many other plant pathogens, P. ananatis does not possess Type 2 Secretion System (T2SS) and Type 3 Secretion System (T3SS) [9].

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