Biology Reference
In-Depth Information
Chapter 8
Phospholipids Signaling System in Plant
Innate Immunity
Abstract
Phospholipids are the sources for production of the second messengers
phosphatidic acid (PA), diacylglycerol (DAG), and inositol 1,4,5-trisphosphate (IP
3
),
which are involved in defense signaling system. Phospholipase C (PLC) and phos-
pholipase D (PLD) are the key enzymes involved in generation of the phospholipid
second messengers. G-proteins, Ca
2+
infl ux, nitric oxide (NO), and reactive oxygen
species (ROS) are involved in PAMP elicitors-triggered activation of PLC and PLD.
IP
3
is involved in activation of Ca
2+
signaling system. PA is an important second mes-
senger in activating ROS, jasmonate (JA), abscisic acid (ABA) systems and it also
activates phosphorylation/dephosphorylation in various signaling systems. DAG is
involved in JA biosynthesis and ROS signaling system. Biphasic production of PA
and ROS through distinctly different phospholipase pathways has been reported.
Protein kinases and phosphatases play key roles in phospholipid signaling system.
Keywords
Phosphatidic acid (PA) • Diacetylglycerol (DAG) • Inositol 1,4,5-
trisphosphate (IP3) • Phospholipases • Protein kinases • Phosphorylation • Second
messengers
8.1
Biosynthesis of Phospholipids-Derived Second
Messengers
Phospholipids are the structural components of cell membranes and they are also
sources of second messengers involved in defense signaling system. Many different
phospholipids can be cleaved by phospholipases to generate second messengers
(Berridge
1984
; Chasan
1995
). Phospholipase C (PLC) and phospholipase D (PLD)
are the key enzymes involved in generation of various phospholipid second mes-
sengers Munnik et al.
1998b
). In the phospholipase C-mediated pathway for the
generation of second messengers (Fig.
8.1
), PLC hydrolyzes the signaling phos-
pholipids (PLs) phosphatidylinositol 4-phosphate (PIP) or phosphatidylinositol
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