Affiliation:
1. Department of Plant Pathology and Center for Microbial Pathogenesis, Michigan State University, 103 Center for Integrated Plant Systems, East Lansing, Michigan 48824
Abstract
ABSTRACT
The enterobacterium
Erwinia amylovora
is a devastating plant pathogen causing necrotrophic fire blight disease of apple, pear, and other rosaceous plants. In this study, we used a modified in vivo expression technology system to identify
E. amylovora
genes that are activated during infection of immature pear tissue, a process that requires the major pathogenicity factors of this organism. We identified 394 unique pear fruit-induced (
pfi
) genes on the basis of sequence similarity to known genes and separated them into nine putative function groups including host-microbe interactions (3.8%), stress response (5.3%), regulation (11.9%), cell surface (8.9%), transport (13.5%), mobile elements (1.0%), metabolism (20.3%), nutrient acquisition and synthesis (15.5%), and unknown or hypothetical proteins (19.8%). Known virulence genes, including
hrp/hrc
components of the type III secretion system, the major effector gene
dspE
, type II secretion, levansucrase (
lsc
), and regulators of levansucrase and amylovoran biosynthesis, were upregulated during pear tissue infection. Known virulence factors previously identified in
E
. (
Pectobacterium
)
carotovora
and
Pseudomonas syringae
were identified for the first time in
E. amylovora
and included HecA hemagglutinin family adhesion, Peh polygalacturonase, new effector HopPtoC
EA
, and membrane-bound lytic murein transglycosylase MltE
EA
. An insertional mutation within
hopPtoC
EA
did not result in reduced virulence; however, an
mltE
EA
knockout mutant was reduced in virulence and growth in immature pears. This study suggests that
E. amylovora
utilizes a variety of strategies during plant infection and to overcome the stressful and poor nutritional environment of its plant hosts.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
124 articles.
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