In plantacomparative transcriptomics of host-adapted strains ofRalstonia solanacearum

Abstract

Background. Ralstonia solanacearum is an economically important plant pathogen with an unusually large host range. The Moko (banana) and NPB (not pathogenic to banana) strain groups are closely related but are adapted to distinct hosts. Previous comparative genomics studies uncovered very few differences that could account for the host range difference between these pathotypes. To better understand the basis of this host specificity, we used RNAseq to profile the transcriptomes of an R. solanacearum Moko strain and an NPB strain under in vitro and in planta conditions.Results. RNAs were sequenced from bacteria grown in rich and minimal media, and from bacteria extracted from mid-stage infected tomato, banana and melon plants. We computed differential expression between each pair of conditions to identify constitutive and host-specific gene expression differences between Moko and NPB. We found that type III secreted effectors were globally up-regulated upon plant cell contact in the NPB strain compared with the Moko strain. Genes encoding siderophore biosynthesis and nitrogen assimilation genes were highly up-regulated in the NPB strain during melon pathogenesis, while denitrification genes were up-regulated in the Moko strain during banana pathogenesis. The relatively lower expression of oxidases and the denitrification pathway during banana pathogenesis suggests that R. solanacearum experiences higher oxygen levels in banana pseudostems than in tomato or melon xylem.Conclusions. This study provides the first report of differential gene expression associated with host range variation. Despite minimal genomic divergence, the pathogenesis of Moko and NPB strains is characterized by striking differences in expression of virulence- and metabolism-related genes.

Plant–phytopathogen interactions: bacterial responses to environmental and plant stimuli

“…Analysis of xylem sap from different plant species showed potassium as the most abundant mineral nutrient, followed by nitrate and chloride (Fatima and Senthil‐Kumar, ). Global expression analyses have been used to understand how R. solanacearum survives and succeeds within the host xylem (Brown and Allen, ; Jacobs et al ., ; Ailloud et al ., ). In an initial study using in vivo expression technology, 153 unique genes were shown to be induced in planta (Brown and Allen, ).…”

“…R. solanacearum phylotypes partly explain the broad host range of this species complex and differential gene expression associated with host range variation has been reported recently (Ailloud et al ., ). Two closely related strains belonging to distinct R. solanacearum pathotypes were compared; a Moko strain (pathogenic to banana but not to cucurbits) and a NPB strain (pathogenic to cucurbits but not to banana).…”

Identification of Cyclic Dipeptides from Escherichia coli as New Antimicrobial Agents against Ralstonia Solanacearum

“…R. solanacearum has an unusually wide host range, infecting more than 200 species belonging to more than 54 botanical families, including economically-important crops [ 2 , 3 , 4 ]. It represents a heterogeneous group subdivided into five races based on host range, five biovars based on physiological and biochemical characteristics [ 5 , 6 ], and four phylotypes roughly corresponding to geographic origin [ 7 , 8 ]. It can survive in soil for many years and can spread through water, rhizosphere contact, and farming [ 9 ].…”

Contribution of a lectin, LecM, to the quorum sensing signalling pathway of Ralstonia solanacearum strain OE1‐1

“…Ailloud et al . () performed transcriptome analyses of R. solanacearum strains infecting host plants using RNA‐seq, and many virulence‐related genes were differentially expressed during infection, compared with in vitro growth, such as growth on a rich medium. A large majority of the PhcA controlled genes followed the same regulation pattern in both rich medium in vitro and after in planta growth, except for a set of HrpG‐HrpB regulated genes, including the type III secretion machinery and type III effectors, whose genes appeared to be specifically induced by PhcA in the plant environment, whereas this regulator repressed their expression in rich medium (Perrier et al ., ).…”