Biology Reference
In-Depth Information
PAMP
Perception
PRR
Ca
2+
influx
PAD4
CaM
Activation
Ca
2+
CBP60
SID2
SA biosynthesis
Immune responses
Fig. 4.11
Role of calmodulin binding protein CBP60 in induction of salicylic acid biosynthesis
(Adapted from Wang et al.
2009
,
2011
; Wan et al.
2012
)
Ca
2+
infl ux and subsequent Ca
2+
wave (calcium signature) may activate NADPH
oxidase and H
2
O
2
production (Zhao and Sakai
2003
). Calcium ion infl ux - induced
H
2
O
2
production triggers increases in lipoxygenase activity (Zhao and Sakai
2003
).
Lipoxygenase is an important enzyme in the octadecanoid pathway leading to the
biosynthesis of jasmonate (Fig.
4.12
; Schaller
2001
; Vidhyasekaran
2007
).
Exogenous application of H
2
O
2
has been found to induce the biosynthesis of endog-
enous jasmonate and initiate the JA pathway triggering downstream defense
responses (Zhao and Sakai
2003
). These studies suggest that Ca
2+
infl ux may be
involved in activation of JA signaling system.
Calcium-dependent protein kinases (CDPKs) are unique enzymes found in
plants and they are characterized as [Ca
2+
]
cyt
sensors in plants. The
Arabidopsis
CDPK CPK6, has been shown to function as [Ca
2+
]
cyt
sensor in the methyl jasmo-
nate (MeJA) signaling (Munemasa et al.
2011
). CPK6 has been found to be essential
for the regulation of plasma membrane Ca
2+
- permeable channel activity
(Munemasa et al.
2011
). MeJA signaling is involved in stomatal closure (Suhita
et al.
2003
), a plant immune response against bacterial pathogens and CPK6
functions as a positive regulator of MeJA signaling (Munemasa et al.
2011
).
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