title: Biochemical characterization of the tomato phosphatidylinositol-specific phospholipase C (PI-PLC) family and its role in plant immunity.
abstract: Plants possess effective mechanisms to quickly respond to biotic and abiotic stresses. The rapid activation of phosphatidylinositol-specific phospholipase C (PLC) enzymes occurs early after the stimulation of plant immune-receptors. Genomes of different plant species encode multiple PLC homologs belonging to one class, PLCζ. Here we determined whether all tomato homologs encode active enzymes and whether they can generate signals that are distinct from one another. We searched the recently completed tomato (Solanum lycopersicum) genome sequence and identified a total of seven PLCs. Recombinant proteins were produced for all tomato PLCs, except for SlPLC7. The purified proteins showed typical PLC activity, as different PLC substrates were hydrolysed to produce diacylglycerol. We studied SlPLC2, SlPLC4 and SlPLC5 enzymes in more detail and observed distinct requirements for Ca(2+) ions and pH, for both their optimum activity and substrate preference. This indicates that each enzyme could be differentially and specifically regulated in vivo, leading to the generation of PLC homolog-specific signals in response to different stimuli. PLC overexpression and specific inhibition of PLC activity revealed that PLC is required for both specific effector- and more general "pattern"-triggered immunity. For the latter, we found that both the flagellin-triggered response and the internalization of the corresponding receptor, Flagellin Sensing 2 (FLS2) of Arabidopsis thaliana, are suppressed by inhibition of PLC activity. Altogether, our data support an important role for PLC enzymes in plant defence signalling downstream of immune receptors. This article is part of a Special Issue entitled: Plant Lipid Biology edited by Kent D. Chapman and Ivo Feussner.
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Abd-El-Haliem
authors.affiliation: Laboratory of Plant Breeding, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Jack H
authors.initials: JH
authors.lastname: Vossen
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Arjan
authors.initials: A
authors.lastname: van Zeijl
authors.affiliation: Laboratory of Plant Breeding, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Sara
authors.initials: S
authors.lastname: Dezhsetan
authors.affiliation: Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
authors.forename: Christa
authors.initials: C
authors.lastname: Testerink
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Seidl
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Martina
authors.initials: M
authors.lastname: Beck
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: James
authors.initials: J
authors.lastname: Strutt
authors.affiliation: The Sainsbury Laboratory, Norwich Research Park, Norwich NR4 7UH, UK.
authors.forename: Silke
authors.initials: S
authors.lastname: Robatzek
authors.affiliation: Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands. Electronic address: matthieu.joosten@wur.nl.
authors.forename: Matthieu H A J
authors.initials: MHAJ
authors.lastname: Joosten
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D018551:Solanum lycopersicum / Q000201:enzymology / Q000235:genetics*; D005810:Multigene Family; D054801:Phosphoinositide Phospholipase C / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D057865:Plant Immunity / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D011494:Protein Kinases; C411853:FLS2 protein, Arabidopsis; D054801:Phosphoinositide Phospholipase C
keywords: Defence response; Immune receptors; PLC enzymes; Phospholipids; Signal transduction