Expression profiles of differentially regulated genes during the early stages of apple flower infection with Erwinia amylovora

Abstract

To identify genes involved in the response to the fire blight pathogen Erwinia amylovora in apple (Malus×domestica), expression profiles were investigated using an apple oligo (70-mer) array representing 40, 000 genes. Blossoms of a fire blight-susceptible apple cultivar Gala were collected from trees growing in the orchard, placed on a tray in the laboratory, and spray-inoculated with a suspension of E. amylovora at a concentration of 108 cfu ml−1. Uninoculated detached flowers served as controls at each time point. Expression profiles were captured at three different time points post-inoculation at 2, 8, and 24 h, together with those at 0 h (uninoculated). A total of about 3500 genes were found to be significantly modulated in response to at least one of the three time points. Among those, a total of 770, 855, and 1002 genes were up-regulated, by 2-fold, at 2, 8, and 24 h following inoculation, respectively; while, 748, 1024, and 1455 genes were down-regulated, by 2-fold, at 2, 8, and 24 h following inoculation, respectively. Over the three time points post-inoculation, 365 genes were commonly up-regulated and 374 genes were commonly down-regulated. Both sets of genes were classified based on their functional categories. The majority of up-regulated genes were involved in metabolism, signal transduction, signalling, transport, and stress response. A number of transcripts encoding proteins/enzymes known to be up-regulated under particular biotic and abiotic stress were also up-regulated following E. amylovora treatment. Those up- or down-regulated genes encode transcription factors, signaling components, defense-related, transporter, and metabolism, all of which have been associated with disease responses in Arabidopsis and rice, suggesting similar response pathways are involved in apple blossoms.

Pathogenicity and infection strategies of the fire blight pathogen Erwinia amylovora in Rosaceae: State of the art

“…Sarowar et al (2011) for instance obtained a total of 3500 genes involved in metabolism, signal transduction and stress response, which were significantly modulated in fireblight-infected blossoms of the apple cultivar 'Gala' and which indicates that several pathways are affected as a result of a successful infection with E. amylovora. Probably one of the earliest responses of a plant to fire blight is a rapid increase of reactive oxygen species (ROS), followed by the production of several secondary metabolites, plant hormones and components of other defence-related pathways, of which some are discussed here more in detail and are represented in Fig.…”

Transcriptomics Analysis of Apple Leaves in Response to Alternaria alternata Apple Pathotype Infection

“…Apple is not just an agronomically important crop; it is also a model species within Rosaceace (Shulaev et al, 2008). Although, several studies to date have analyzed apple-pathogen interactions (Sarowar et al, 2011; Vilanova et al, 2014), this study is the first global transcription analysis of apple in response to AAAP.…”

Molecular response of resistant and susceptible apple genotypes to Erwinia amylovora infection

“…Gala is highly susceptible to fire blight (Sobiczewski et al 2004), this shows that induction of PR genes alone is not providing resistance to the pathogen. Sarowar et al (2011) analysed gene expression in the E. amylovorachallenged blossoms of cv. Gala using an apple oligo (70-mer) arrays.…”

“…Venisse et al (2001) have demonstrated that in the pear leaves challenged with E. amylovora the activity of GST increased, together with other antioxidant enzymes like ascorbate peroxidase (AsPOX), glutathione reductase (GR) and peroxidase (POX). Interestingly, Sarowar et al (2011) reported that glutathione S-transferase was suppressed in apple blossoms of cv. Gala following E. amylovora inoculation.…”