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Fig. 4.6
Role of calmodulin
in Ca
2+
-triggered ROS
generation
Calcium influx
Calcium signature
Calmodulin gene activation
Calmodulin
Ca
2+
/CaM complex
Activation
NAD kinase
NADPH
Activation
NADPH oxidase
ROS
4.14.7
Catalases as CaM-Binding Proteins
CaM binds to and activates some plant catalases in the presence of calcium. Ca
2+
/
CaM may down-regulate H
2
O
2
levels in plants by stimulating the catalytic activity
of plant catalase. The results suggest that calcium has dual functions in regulating
H
2
O
2
homeostasis, which in turn infl uences redox signaling in plants (Yang and
Poovaiah
2002b
). Redox signaling system has been reported to be involved in plant
defense response against pathogens (Önnerud et al.
2002
; Cumming et al.
2004
;
Fobert and Després
2005
; Fedoroff
2006
).
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