International Network of Plant Abiotic Stress

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Phospholipids have long been known for their key role in maintaining the bilayerstructure of membranes and in physically separating the cytosol from organelles and the extracellular space. In the past decade, a completely novel and unexpected function emerged, fullfilling a crucial role in cell signalling. It was the discovery in animal cells, that agonist-activated cell surface receptors led to the activation of a phospholipase C (PLC), to hydrolyze the minor lipid, phosphatidylinositol 4,5-bisphosphate into two second messengers, inositol 1,4,5-trisphosphate (InsP₃) and diacylglycerol (DAG). While InsP₃ diffuses into the cytosol, where it releases Ca²⁺ from an intracellular store by activating a ligand-gated Ca²⁺-channel, DAG remains in the membrane to recruit and activate members of the protein kinase C family.

Over the years, a variety of other lipid based-signalling cascades were discovered. These include, phospholipase A, generating lyso-phospholipids and free fatty acids (to be converted into prostaglandins and leukotrienes), phospholipase D, to generate the lipid second messenger, phosphatidic acid (PA), and phosphoinositide 3-kinase (PI3K), generating a distinct set of polyphosphoinositides (PPI) phosphorylated at the D3-position of the inositol ring, all with separate signalling functions. Sphingolipids, representing another important group of signalling lipids, also came across.

The majority of these lipid-based signalling pathways have been discovered in plant cells too. Moreover, they have been found to be activated in response to a wide variety of biotic and abiotic stress signals, but also to be basically involved in plant growth and development. While many of the enzymes, lipids, and their targets involved are well conserved, major differences with the mammalian paradigms have also emerged.

This book highlights the current status of plant lipid signalling. All chapters have been written by experts in the field and cover information for both beginners and advanced lipidologists. Chapters include phospholipases (Chaps. 1-3), lipid kinases (Chaps. 4-7), lipid phosphatases (Chaps. 8-9), inositolphosphates and PPI metabolism (Chaps. 10-13), PA signalling (Chaps. 14-17), and additional lipid signals, e.g. oxylipins, NAPE and sphingolipids (Chaps 18-20).