Cells sense a variety of extracellular signals balancing their metabolism and physiology according to changing growth conditions. Plasma membranes are the outermost informational barriers that render cells sensitive to regulatory inputs. Membranes are composed of different types of lipids that play not only structural but also informational roles. Hormones and other regulators are sensed by specific receptors leading to the activation of lipid metabolizing enzymes. These enzymes generate lipid second messengers. Among them, phosphatidic acid (PA) is a well-known intracellular messenger that regulates various cellular processes. This lipid affects the functional properties of cell membranes and binds to specific target proteins leading to either genomic (affecting transcriptome) or non-genomic responses. The subsequent biochemical, cellular and physiological reactions regulate plant growth, development and stress tolerance. In the present review, we focus on primary (genome-independent) signaling events triggered by rapid PA accumulation in plant cells and describe the functional role of PA in mediating response to hormones and hormone-like regulators. The contributions of individual lipid signaling enzymes to the formation of PA by specific stimuli are also discussed. We provide an overview of the current state of knowledge and future perspectives needed to decipher the mode of action of PA in the regulation of cell functions.

• Keywords
• autophagy, biologically active substance, diacylglycerol kinase, phosphatidic acid, phospholipase, phospholipid, signal transduction, targets,
• MeSH
• Phospholipase D * metabolism   MeSH
• Hormones metabolism   MeSH
• Phosphatidic Acids * metabolism   MeSH
• Proteins metabolism   MeSH
• Plant Proteins genetics   MeSH
• Plants metabolism   MeSH
• Signal Transduction physiology   MeSH
• Plant Development MeSH
• Publication type
• Journal Article MeSH
• Review MeSH
• Names of Substances
• Phospholipase D * MeSH
• Hormones MeSH
• Phosphatidic Acids * MeSH
• Proteins MeSH
• Plant Proteins MeSH

Phospholipases (PLs) are lipid-hydrolyzing enzymes known to have diverse signaling roles during plant abiotic and biotic stress responses. They catalyze lipid remodeling, which is required to generate rapid responses of plants to environmental cues. Moreover, they produce second messenger molecules, such as phosphatidic acid (PA) and thus trigger or modulate signaling cascades that lead to changes in gene expression. The roles of phospholipases in plant abiotic and biotic stress responses have been intensively studied. Nevertheless, emerging evidence suggests that they also make significant contributions to plants' cellular and developmental processes. In this mini review, we summarized recent advances in the study of the cellular and developmental roles of phospholipases in plants.

• Keywords
• cellular functions, phosphatidic acid, phospholipase A, phospholipase C, phospholipase D, phospholipases, phytohormones, plant development,
• Publication type
• Journal Article MeSH
• Review MeSH

Phospholipase D alpha 1 (PLDα1) is a phospholipid hydrolyzing enzyme playing multiple regulatory roles in stress responses of plants. Its signaling activity is mediated by phosphatidic acid (PA) production, capacity to bind, and modulate G-protein complexes or by interaction with other proteins. This work presents a quantitative proteomic analysis of two T-DNA insertion pldα1 mutants of Arabidopsis thaliana. Remarkably, PLDα1 knockouts caused differential regulation of many proteins forming protein complexes, while PLDα1 might be required for their stability. Almost one third of differentially abundant proteins (DAPs) in pldα1 mutants are implicated in metabolism and RNA binding. Latter functional class comprises proteins involved in translation, RNA editing, processing, stability, and decay. Many of these proteins, including those regulating chloroplast protein import and protein folding, share common functions in chloroplast biogenesis and leaf variegation. Consistently, pldα1 mutants showed altered level of TIC40 (a major regulator of protein import into chloroplast), differential accumulation of photosynthetic protein complexes and changed chloroplast sizes as revealed by immunoblotting, blue-native electrophoresis, and microscopic analyses, respectively. Our proteomic analysis also revealed that genetic depletion of PLDα1 also affected proteins involved in cell wall architecture, redox homeostasis, and abscisic acid signaling. Taking together, PLDα1 appears as a protein integrating cytosolic and plastidic protein translations, plastid protein degradation, and protein import into chloroplast in order to regulate chloroplast biogenesis in Arabidopsis.

• Keywords
• Arabidopsis, chloroplast biogenesis, chloroplast protein import, phospholipase D alpha 1, proteomics, translation,
• Publication type
• Journal Article MeSH

Phospholipase Dα1 (PLDα1) belongs to phospholipases, a large phospholipid hydrolyzing protein family. PLDα1 has a substrate preference for phosphatidylcholine leading to enzymatic production of phosphatidic acid, a lipid second messenger with multiple cellular functions. PLDα1 itself is implicated in biotic and abiotic stress responses. Here, we present a shot-gun differential proteomic analysis on roots of two Arabidopsis pldα1 mutants compared to the wild type. Interestingly, PLDα1 deficiency leads to altered abundances of proteins involved in diverse processes related to membrane transport including endocytosis and endoplasmic reticulum-Golgi transport. PLDα1 may be involved in the stability of attachment sites of endoplasmic reticulum to the plasma membrane as suggested by increased abundance of synaptotagmin 1, which was validated by immunoblotting and whole-mount immunolabelling analyses. Moreover, we noticed a robust abundance alterations of proteins involved in mitochondrial import and electron transport chain. Notably, the abundances of numerous proteins implicated in glucosinolate biosynthesis were also affected in pldα1 mutants. Our results suggest a broader biological involvement of PLDα1 than anticipated thus far, especially in the processes such as endomembrane transport, mitochondrial protein import and protein quality control, as well as glucosinolate biosynthesis.

• Keywords
• Arabidopsis, cytoskeleton, mitochondrial protein import, phospholipase D alpha1, proteomics, quality control, vesicular transport,
• MeSH
• Arabidopsis metabolism   MeSH
• Endocytosis MeSH
• Phospholipase D genetics   metabolism   MeSH
• Gene Ontology MeSH
• Glucosinolates biosynthesis   MeSH
• Plant Roots metabolism   MeSH
• Mitochondrial Proteins metabolism   MeSH
• Arabidopsis Proteins genetics   metabolism   MeSH
• Proteome metabolism   MeSH
• Proteomics * MeSH
• Synaptotagmin I metabolism   MeSH
• Tandem Mass Spectrometry MeSH
• Protein Transport MeSH
• Uncoupling Protein 1 metabolism   MeSH
• Chromatography, High Pressure Liquid MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Phospholipase D MeSH
• Glucosinolates MeSH
• Mitochondrial Proteins MeSH
• PLDA1 protein, Arabidopsis MeSH Browser
• Arabidopsis Proteins MeSH
• Proteome MeSH
• Synaptotagmin I MeSH
• SYT1 protein, Arabidopsis MeSH Browser
• Uncoupling Protein 1 MeSH

BACKGROUND AND AIMS: The non-specific phospholipase C (NPC) is a new member of the plant phospholipase family that reacts to abiotic environmental stresses, such as phosphate deficiency, high salinity, heat and aluminium toxicity, and is involved in root development, silicon distribution and brassinolide signalling. Six NPC genes (NPC1-NPC6) are found in the Arabidopsis genome. The NPC2 isoform has not been experimentally characterized so far. METHODS: The Arabidopsis NPC2 isoform was cloned and heterologously expressed in Escherichia coli. NPC2 enzyme activity was determined using fluorescent phosphatidylcholine as a substrate. Tissue expression and subcellular localization were analysed using GUS- and GFP-tagged NPC2. The expression patterns of NPC2 were analysed via quantitative real-time PCR. Independent homozygous transgenic plant lines overexpressing NPC2 under the control of a 35S promoter were generated, and reactive oxygen species were measured using a luminol-based assay. KEY RESULTS: The heterologously expressed protein possessed phospholipase C activity, being able to hydrolyse phosphatidylcholine to diacylglycerol. NPC2 tagged with GFP was predominantly localized to the Golgi apparatus in Arabidopsis roots. The level of NPC2 transcript is rapidly altered during plant immune responses and correlates with the activation of multiple layers of the plant defence system. Transcription of NPC2 decreased substantially after plant infiltration with Pseudomonas syringae, flagellin peptide flg22 and salicylic acid treatments and expression of the effector molecule AvrRpm1. The decrease in NPC2 transcript levels correlated with a decrease in NPC2 enzyme activity. NPC2-overexpressing mutants showed higher reactive oxygen species production triggered by flg22. CONCLUSIONS: This first experimental characterization of NPC2 provides new insights into the role of the non-specific phospholipase C protein family. The results suggest that NPC2 is involved in the response of Arabidopsis to P. syringae attack.

• Keywords
• Arabidopsis thaliana, MAMP-triggered immunity, Pseudomonas syringae, effector-triggered immunity, flagellin, non-specific phospholipase C, phosphatidylcholine-specific phospholipase C, reactive oxygen species,
• MeSH
• Arabidopsis enzymology   immunology   microbiology   MeSH
• Phosphatidylcholines metabolism   MeSH
• Type C Phospholipases genetics   physiology   MeSH
• Golgi Apparatus enzymology   MeSH
• Plant Immunity physiology   MeSH
• Cloning, Molecular MeSH
• Microscopy, Confocal MeSH
• Real-Time Polymerase Chain Reaction MeSH
• Plant Diseases immunology   microbiology   MeSH
• Arabidopsis Proteins genetics   physiology   MeSH
• Protoplasts enzymology   MeSH
• Pseudomonas syringae * MeSH
• Reactive Oxygen Species MeSH
• Gene Expression Regulation, Plant MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Phosphatidylcholines MeSH
• Type C Phospholipases MeSH
• NPC2 protein, Arabidopsis MeSH Browser
• Arabidopsis Proteins MeSH
• Reactive Oxygen Species MeSH

To achieve host colonization, successful pathogens need to overcome plant basal defences. For this, (hemi)biotrophic pathogens secrete effectors that interfere with a range of physiological processes of the host plant. AvrLm4-7 is one of the cloned effectors from the hemibiotrophic fungus Leptosphaeria maculans 'brassicaceae' infecting mainly oilseed rape (Brassica napus). Although its mode of action is still unknown, AvrLm4-7 is strongly involved in L. maculans virulence. Here, we investigated the effect of AvrLm4-7 on plant defence responses in a susceptible cultivar of B. napus. Using two isogenic L. maculans isolates differing in the presence of a functional AvrLm4-7 allele [absence ('a4a7') and presence ('A4A7') of the allele], the plant hormone concentrations, defence-related gene transcription and reactive oxygen species (ROS) accumulation were analysed in infected B. napus cotyledons. Various components of the plant immune system were affected. Infection with the 'A4A7' isolate caused suppression of salicylic acid- and ethylene-dependent signalling, the pathways regulating an effective defence against L. maculans infection. Furthermore, ROS accumulation was decreased in cotyledons infected with the 'A4A7' isolate. Treatment with an antioxidant agent, ascorbic acid, increased the aggressiveness of the 'a4a7' L. maculans isolate, but not that of the 'A4A7' isolate. Together, our results suggest that the increased aggressiveness of the 'A4A7' L. maculans isolate could be caused by defects in ROS-dependent defence and/or linked to suppressed SA and ET signalling. This is the first study to provide insights into the manipulation of B. napus defence responses by an effector of L. maculans.

• Keywords
• AvrLm4-7, Brassica napus, Leptosphaeria, ROS, effector, ethylene, salicylic acid,
• MeSH
• Alleles MeSH
• Antioxidants pharmacology   MeSH
• Ascomycota drug effects   isolation & purification   metabolism   MeSH
• Brassica napus drug effects   growth & development   metabolism   microbiology   MeSH
• Chromatography, Liquid MeSH
• Cyclopentanes metabolism   MeSH
• Ethylenes metabolism   MeSH
• Fungal Proteins metabolism   MeSH
• Mass Spectrometry MeSH
• Host-Pathogen Interactions drug effects   MeSH
• Cotyledon drug effects   metabolism   microbiology   MeSH
• Abscisic Acid metabolism   MeSH
• Ascorbic Acid pharmacology   MeSH
• Salicylic Acid metabolism   MeSH
• Oxylipins metabolism   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Reverse Transcriptase Polymerase Chain Reaction MeSH
• Plant Growth Regulators metabolism   MeSH
• Signal Transduction * drug effects   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Antioxidants MeSH
• Cyclopentanes MeSH
• Ethylenes MeSH
• Fungal Proteins MeSH
• jasmonic acid MeSH Browser
• Abscisic Acid MeSH
• Ascorbic Acid MeSH
• Salicylic Acid MeSH
• Oxylipins MeSH
• Hydrogen Peroxide MeSH
• Plant Growth Regulators MeSH