Agriculture Reference
In-Depth Information
Fig. 8.1.
Representation of NO signaling functions during the hypersensitive response.
Dashed lines
represent potential NO functions;
solid lines
represent experimental supported
results.
Av r
avirulence signal,
CHS
chalcone synthase,
C
4
H
cinnamic acid-4-hydroxylase,
CA
cinnamic acid,
Ca
2+
calcium influx,
cADPR
cyclic ADP ribose,
cGMP
cyclic GMP,
GSNO
S
-nitroso-l-glutathione,
PAL
phenylalanine ammonia lyase,
PHE
phenylalanine,
PR pro-
teins
pathogenesis-related proteins,
R
receptor,
SA
salicylic acid,
SAR
systemic acquired
resistance,
SOD
superoxide dismutase
blockers for Ca
2+
channels and anion channels, suggesting that the initial
ion fluxes are crucial for the induction of defense responses (Wendehenne
et al. 2002).
8.3
NO Production During the Hypersensitive
Disease Resistance Response
In mammals, biosynthesis of NO is primarily catalyzed by NO synthase
(NOS) by oxidation of l-arginine to l-citrulline and NO. In plants, NO
can be produced through both nonenzymatic and enzymatic routes. The
former include the light-mediated conversion of NO
2
to NO catalyzed by
carotenoids (Cooney et al. 1994). Liberation of NO occurs from nitrite
at neutral pH (Yamasaki and Sakihama 2000). Other nonenzymatic reac-
tions occur at acidic pH and in the presence of reducing agents such as
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