Biology Reference
In-Depth Information
2.6.10
Superoxide Dismutase (SOD) as a PAMP
A protein of the extracellular proteome of
Xanthomonas campestris
pv.
campestris
was identifi ed as a PAMP. The protein PAMP was a superoxide dismutase (SodM).
It elicited H
2
O
2
production in tobacco cell cultures. The amino acid sequence of this
protein was found to be responsible for the elicitation of the oxidative burst reaction
(Watt et al.
2006
).
2.6.11
Bacterial DNA as PAMP
Elicitor activity of bacterial DNA has been demonstrated on the model plant
Arabidopsis thaliana
.
Eco
RI-digested plasmid DNA induced generation of ROS
generation and deposition of callose, whereas
Sm
a1- and
Hap
II-digested plasmid
DNA and
Eco
RI-digested herring DNA did not remarkably induce these
responses (Yakushiji et al.
2009
). Further, methylation of the CpG sequence of
plasmid DNA and
Escherichia coli
DNA reduced the level of the defense
responses (Yakushiji et al.
2009
). These results suggest that the nonmethylated
CpG DNA is a PAMP/MAMP. The non-methylated DNA of the bacteria seems
to be translocated into the cytoplasm of plant cells by endocytosis, as the endo-
cytosis inhibitors signifi cantly inhibited DNA-induced defense responses
(Yakushiji et al.
2009
).
2.6.12
NEP1-Like Proteins as Bacterial PAMPs
Nep1-like proteins (NLPs) have been detected in some bacterial pathogens,
including
Pectobacterium carotovorum
subsp.
carotovorum
(Mattinen et al.
2004
; Kufner et al.
2009
) and
P. carotovorum
subsp.
atrosepticum
(Pemberton
et al.
2005
). These proteins were shown to be virulence factors (Ottmann et al.
2009
) and these NLPs also trigger immune responses. The NLPs have dual func-
tions, acting both as triggers of immune responses and as toxin-like virulence
factors (Ottmann et al.
2009
).
2.7
Fungal PAMPs
2.7.1
Chitooligosaccharides as PAMPs
Several PAMPs have been detected in various plant fungal pathogens. Chitin,
(
4-linked polymer of
N
-acetylglucosamine; GlcNAc), is a major component
of fungal cell walls. It is not found in plants; however the plants secrete
β
-1
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