Soft rot erwiniae: from genes to genomes
Ian K. Toth*, Kenneth S. Bell, Maria C. Holeva and Paul R. J. Birch
Plant-Pathogen Interactions Programme, Scottish Crop Research Institute,
Invergowrie, Dundee DD2 5DA, UK
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| Summary: |
The soft rot erwiniae, Erwinia
carotovora ssp. atroseptica (Eca), E. carotovora
ssp. carotovora (Ecc) and E. chrysanthemi (Ech)
are major bacterial pathogens of potato and other crops world-wide. We
currently understand much about how these bacteria attack plants and
protect themselves against plant defences. However, the processes
underlying the establishment of infection, differences in host range and
their ability to survive when not causing disease, largely remain a
mystery. This review will focus on our current knowledge of pathogenesis
in these organisms and discuss how modern genomic approaches, including
complete genome sequencing of Eca and Ech, may open the door
to a new understanding of the potential subtlety and complexity of soft
rot erwiniae and their interactions with plants. |
| Taxonomy: |
The soft rot erwiniae are members
of the Enterobacteriaceae, along with other plant pathogens such as
Erwinia amylovora and human pathogens such as Escherichia coli,
Salmonella spp. and Yersinia spp. Although the genus name Erwinia
is most often used to describe the group, an alternative genus name Pectobacterium
was recently proposed for the soft rot species. |
| Host Range: |
Ech mainly affects crops and
other plants in tropical and subtropical regions and has a wide host range
that includes potato and the important model host African violet (Saintpaulia
ionantha). Ecc affects crops and other plants in subtropical
and temperate regions and has probably the widest host range, which also
includes potato. Eca, on the other hand, has a host range limited
almost exclusively to potato in temperate regions only. |
| Disease symptoms: |
Soft rot erwiniae cause general
tissue maceration, termed soft rot disease, through the production of
plant cell wall degrading enzymes. Environmental factors such as
temperature, low oxygen concentration and free water play an essential
role in disease development. On potato, and possibly other plants, disease
symptoms may differ, e.g. blackleg disease is associated more with Eca
and Ech than with Ecc. |
| Useful websites: |
www.scri.sari.ac.uk/TiPP/Erwinia.htm
www.ahabs.wisc.edu:16080/pernalab/erwinia/index.htm
www.tigr.org/tdb/mdb/mdbinprogress.html
www.sanger.ac.uk/Projects/E_carotovora/ |
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(a) Comparison of healthy potato plant (left) and plant infected with Erwinia
carotovora ssp. atroseptica (right) showing severe wilting and
stem rot due to blackleg disease (see base of stem). (b) African violet (Saintpaulia
ionantha) leaf infected with Erwinia chrysanthemi. (c) Growth
of soft rot erwinia on crystal violet pectate (CVP) medium showing
characteristic cavities formed by the production of exoenzymes. (d) In
planta virulence screening assay by stab inoculation of Erwinia
carotovora subsp. atroseptica into potato stems showing
increasing severity from left to right.
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