Phospholipids Signaling System in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 376

Elicitor

Activation of PLC-
DAG pathway

Activation of PLD
pathway

Second phase of PA
accumulation

First phase of PA
accumulation

DAG

Binds

Phosphoinositide-dependent
kinase 1 (PDK1)

NADPH
oxidase

NADPH
oxidase

Activation

OXI1 protein kinase

First phase of rapid and low ROS
production

NADPH oxidase

Second phase of prolonged and massive ROS production

Fig. 8.3 Role of phospholipase pathways in biphasic PA and ROS generation in Arabidopsis
(Adapted from Yamaguchi et al. 2005 ; Andersson et al. 2006 )

The oxidative burst mediated by elicitors occurs in two phases (Fig. 8.4 ). The
fi rst phase shows a rapid (5 min onward) and low ROS production whereas the sec-
ond phase shows a prolonged (3-6 h) and massive ROS production (Lamb and
Dixon 1997 ). The biphasic ROS generation in rice cells induced by an elicitor was
associated with the activation of PLC and PLD. The activation of both enzymes was
shown for the fi rst phase of ROS generation, whereas for the second phase only the
activation of PLD was observed (Yamaguchi et al. 2005 ). A biphasic accumulation
of PA has been reported in Arabidopsis on recognition of elicitors (Fig. 8.3 ). The
fi rst wave was attributed to the PLC/DAG kinase pathway and the second to PLD.
Both the phospholipase pathways acted upstream of ROS formation (Andersson
et al. 2006 ). PA accumulated rapidly via PLC/DAG kinase pathway in tobacco cells
treated with an elicitor and PLC activity was required for the rapid ROS accumula-
tion (de Jong et al. 2004 ). The NO-dependent, PLC/DAG kinase-generated PA is
involved in the induction of ROS production (Laxalt et al. 2007 ).