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

The documentation of plant growth and development requires integrative and scalable approaches to investigate and spatiotemporally resolve various dynamic processes at different levels of plant body organization. The present update deals with vigorous developments in mesoscopy, microscopy and nanoscopy methods that have been translated to imaging of plant subcellular compartments, cells, tissues and organs over the past 3 years with the aim to report recent applications and reasonable expectations from current light-sheet fluorescence microscopy (LSFM) and super-resolution microscopy (SRM) modalities. Moreover, the shortcomings and limitations of existing LSFM and SRM are discussed, particularly for their ability to accommodate plant samples and regarding their documentation potential considering spherical aberrations or temporal restrictions prohibiting the dynamic recording of fast cellular processes at the three dimensions. For a more comprehensive description, advances in living or fixed sample preparation methods are also included, supported by an overview of developments in labeling strategies successfully applied in plants. These strategies are practically documented by current applications employing model plant Arabidopsis thaliana (L.) Heynh., but also robust crop species such as Medicago sativa L. and Hordeum vulgare L. Over the past few years, the trend towards designing of integrative microscopic modalities has become apparent and it is expected that in the near future LSFM and SRM will be bridged to achieve broader multiscale plant imaging with a single platform.

• MeSH
• Microscopy, Fluorescence methods   MeSH
• Plant Cells ultrastructure   MeSH
• Plant Development * MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Pattern formation, cell proliferation, and directional cell growth, are driving factors of plant organ shape, size, and overall vegetative development. The establishment of vegetative morphogenesis strongly depends on spatiotemporal control and synchronization of formative and proliferative cell division patterns. In this context, the progression of cell division and the regulation of cell division plane orientation are defined by molecular mechanisms converging to the proper positioning and temporal reorganization of microtubule arrays such as the preprophase microtubule band, the mitotic spindle and the cytokinetic phragmoplast. By focusing on the tractable example of primary root development and lateral root emergence in Arabidopsis thaliana, genetic studies have highlighted the importance of mechanisms underlying microtubule reorganization in the establishment of the root system. In this regard, severe alterations of root growth, and development found in extensively studied katanin1 mutants of A. thaliana (fra2, lue1, and ktn1-2), were previously attributed to defective rearrangements of cortical microtubules and aberrant cell division plane reorientation. How KATANIN1-mediated microtubule severing contributes to tissue patterning and organ morphogenesis, ultimately leading to anisotropy in microtubule organization is a trending topic under vigorous investigation. Here we addressed this issue during root development, using advanced light-sheet fluorescence microscopy (LSFM) and long-term imaging of ktn1-2 mutant expressing the GFP-TUA6 microtubule marker. This method allowed spatial and temporal monitoring of cell division patterns in growing roots. Analysis of acquired multidimensional data sets revealed the occurrence of ectopic cell divisions in various tissues including the calyptrogen and the protoxylem of the main root, as well as in lateral root primordia. Notably the ktn1-2 mutant exhibited excessive longitudinal cell divisions (parallel to the root axis) at ectopic positions. This suggested that changes in the cell division pattern and the occurrence of ectopic cell divisions contributed significantly to pleiotropic root phenotypes of ktn1-2 mutant. LSFM provided evidence that KATANIN1 is required for the spatiotemporal control of cell divisions and establishment of tissue patterns in living A. thaliana roots.

• Keywords
• Arabidopsis, ectopic cell division, katanin, light-sheet fluorescence microscopy, live cell imaging, microtubules, root development,
• Publication type
• Journal Article MeSH

Plant phospholipase Ds (PLDs), essential regulators of phospholipid signaling, function in multiple signal transduction cascades; however, the mechanisms regulating PLDs in response to pathogens remain unclear. Here, we found that Arabidopsis (Arabidopsis thaliana) PLDδ accumulated in cells at the entry sites of the barley powdery mildew fungus, Blumeria graminis f. sp hordei Using fluorescence recovery after photobleaching and single-molecule analysis, we observed higher PLDδ density in the plasma membrane after chitin treatment; PLDδ also underwent rapid exocytosis. Fluorescence resonance energy transfer with fluorescence lifetime imaging microscopy showed that the interaction between PLDδ and the microdomain marker AtREMORIN1.3 (AtREM1.3) increased in response to chitin, indicating that exocytosis facilitates rapid, efficient sorting of PLDδ into microdomains upon pathogen stimulus. We further unveiled a trade-off between brefeldin A (BFA)-resistant and -sensitive pathways in secretion of PLDδ under diverse conditions. Upon pathogen attack, PLDδ secretion involved syntaxin-associated VAMP721/722-mediated exocytosis sensitive to BFA. Analysis of phosphatidic acid (PA), hydrogen peroxide, and jasmonic acid (JA) levels and expression of related genes indicated that the relocalization of PLDδ is crucial for its activation to produce PA and initiate reactive oxygen species and JA signaling pathways. Together, our findings revealed that the translocation of PLDδ to papillae is modulated by exocytosis, thus triggering PA-mediated signaling in plant innate immunity.plantcell;31/12/3015/FX1F1fx1.

• MeSH
• Arabidopsis genetics   immunology   metabolism   microbiology   MeSH
• Ascomycota pathogenicity   MeSH
• Brefeldin A immunology   metabolism   MeSH
• Cell Membrane metabolism   MeSH
• Chitin immunology   metabolism   MeSH
• Cyclopentanes metabolism   MeSH
• Exocytosis drug effects   immunology   MeSH
• Phospholipase D genetics   metabolism   MeSH
• Phosphatidic Acids metabolism   MeSH
• Plant Diseases immunology   microbiology   MeSH
• Oxylipins metabolism   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Immunity, Innate * drug effects   MeSH
• Arabidopsis Proteins metabolism   MeSH
• Qa-SNARE Proteins metabolism   MeSH
• R-SNARE Proteins metabolism   MeSH
• SNARE Proteins genetics   metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Signal Transduction immunology   physiology   MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Brefeldin A MeSH
• Chitin MeSH
• Cyclopentanes MeSH
• Phospholipase D MeSH
• jasmonic acid MeSH Browser
• Phosphatidic Acids MeSH
• Oxylipins MeSH
• PEN1 protein, Arabidopsis MeSH Browser
• Hydrogen Peroxide MeSH
• phospholipase D delta MeSH Browser
• Arabidopsis Proteins MeSH
• Qa-SNARE Proteins MeSH
• R-SNARE Proteins MeSH
• SNARE Proteins MeSH
• Reactive Oxygen Species MeSH
• REM1 protein, Arabidopsis MeSH Browser
• VAMP721 protein, Arabidopsis MeSH Browser
• VAMP722 protein, Arabidopsis MeSH Browser

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, AT3G15730) and mitogen-activated protein kinases (MAPKs) participate on signaling-dependent events in plants. MAPKs are able to phosphorylate a wide range of substrates putatively including PLDs. Here we have focused on functional regulations of PLDα1 by interactions with MAPKs, their co-localization and impact on salt stress and abscisic acid (ABA) tolerance in Arabidopsis. Yeast two-hybrid and bimolecular fluorescent assays showed that PLDα1 interacts with MPK3. Immunoblotting analyses likewise confirmed connection between both these enzymes. Subcellularly we co-localized PLDα1 with MPK3 in the cortical cytoplasm close to the plasma membrane and in cytoplasmic strands. Moreover, genetic interaction studies revealed that pldα1mpk3 double mutant was resistant to a higher salinity and showed a higher tolerance to ABA during germination in comparison to single mutants and wild type. Thus, this study revealed importance of new biochemical and genetic interactions between PLDα1 and MPK3 for Arabidopsis stress (salt and ABA) response.

• Keywords
• Arabidopsis thaliana, abscisic acid, genetic interaction, localization, mitogen-activated protein kinase 3, phospholipase D alpha 1, protein interaction, salt stress,
• Publication type
• Journal Article 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