Biology Reference
In-Depth Information
PAMP
Activation
Phospholipase D
Regulates
3-phosphoinositide-dependent
protein kinase1
Phosphatidic acid
(PDK1)
Phosphorylation
NADPH oxidase
Oxidative signal-inducible1
(OXI1)
Interaction with
MAPK
Pto kinase interactor 1-2 (PTI1-2)
ROS generation
Fig. 9.2
Role of PDK1 - OXI1 - PTI1 - MAPK mediated phosphorylation events in ROS genera-
tion (Adapted from Rentel et al.
2004
; Anthony et al.
2004
,
2006
)
(Devarenne et al.
2006
; Zegzouti et al.
1999
). PTI1-2 has been found to be an
interacting partner of OXI1, which is downstream of OXI1. Its sequence closely
resembled the tomato Pto kinase, which is involved in triggering programmed cell
death-mediated disease resistance (Anthony et al.
2006
). H
2
O
2
is produced via
OXI1-PTI1-2 pathway (Anthony et al.
2006
). PDK1 enzyme activity is regulated
by phosphatidic acid (PA) (Anthony et al.
2004
). PA is generated via two distinct
phospholipase pathways, either directly by phospholipase D (PLD) or the sequen-
tial action of phospholipase C (PLC) and diaceylglycerol kinase (Testernik and
Munnik
2005
). PDK1 is specifi cally activated by PLD-generated PA (PA
PLD
)
(Anthony et al.
2004
). The lipids signaling pathways converge via the PDK1-OXI1
axis (Anthony et al.
2006
). Thus, three protein kinases (PDK1, OXI1, and PTI1-2)
are involved in phosphorylation-mediated ROS signaling system in
A
.
thaliana
(Anthony et al.
2006
).
Kinase active PTI1-2 is able to increase the expression of ROS promoters
indicating that PTI1-2 functions in specifi c ROS signaling pathways (Anthony et al.
2006
). Oxi1 null mutants are impaired in the activation of the MAPKs MPK3 and
MPK6 upon oxidative stress, suggesting that OXI1 functions downstream of ROS
but upstream of the MAPK module (Rentel et al.
2004
).
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