Phospholipids Signaling System in Plant Innate Immunity - PAMP Signals in Plant Innate Immunity: Signal Perception and Transduction - page 377

Phospholipase C /Acyl hydrolase

PAMP/
Elicitor

Phosphatidic
acid (PA)

Diacyl
glycerol

Free linolenic
acids

Lipoxygenase

Hydroperoxide fatty acid

Phospholipase D

Allene oxide synthase

Jasmonate

Fig. 8.4 Role of phospholipases in jasmonate biosynthesis pathway (Adapted from Wang et al.
2000 )

8.5 Phospholipids in JA Signaling System

PLD-mediated formation of PA may initiate a lipolytic pathway, consisting of PLD,
PA phosphatase, and acyl-hydrolyzing enzymes. In this pathway, phospholipids are
converted sequentially into PA, DAG, and free linoleic acids (Ryu and Wang 1998 ;
Wang et al. 2000 ). The free linolenic acid is the substrate for JA synthesis (Fig. 8.4 ).

8.6 Phospholipid Signaling System in ABA Signaling

Network

Phospholipid signaling system involving phospholipase C, phospholipase D, and
inositol (1,4,5) trisphosphate (IP3) have all been implicated in ABA signaling.
Phospholipase D-mediated phosphatidic acid (PA) production has been shown to
promote ABA-induced gene expression (Zhang et al. 2005 ). Phospholipase D

-1-
derived PA regulates a protein phosphatase 2C, ABI1, which is a negative regulator
of ABA responses in Arabidopsis (Zhang et al. 2004 ). ABA treatment promotes an
increase in PA from phosphatidylcholine. The PA binds to ABI1 and arginine 73 in
ABI1 is essential for PA-ABI1 binding. Binding of PA to ABI1 protein results in
anchorage of ABI1 to the plasma membrane and a decrease in ABI1 PP2C activity.
This membrane tethering reduces the movement of ABI1 from the cytosol into the
nucleus. The lack of ABA-induced production of PA in PLD

α

1 -null cells results in
a decrease in the association of ABI1 with the plasma membrane in response to
ABA (Zhang et al. 2004 ). These results suggest that PA produced by PLD

α

α 1 inhibits