Biosynthesis and functions of very-long-chain fatty acids in the responses of plants to abiotic and biotic stresses

Very-long-chain fatty acids (i.e., fatty acids with more than 18 carbon atoms; VLCFA) are important molecules that play crucial physiological and structural roles in plants. VLCFA are specifically present in several membrane lipids and essential for membrane homeostasis. Their specific accumulation in the sphingolipids of the plasma membrane outer leaflet is of primordial importance for its correct functioning in intercellular communication. VLCFA are found in phospholipids, notably in phosphatidylserine and phosphatidylethanolamine, where they could play a role in membrane domain organization and interleaflet coupling. In epidermal cells, VLCFA are precursors of the cuticular waxes of the plant cuticle, which are of primary importance for many interactions of the plant with its surrounding environment. VLCFA are also major components of the root suberin barrier, which has been shown to be fundamental for nutrient homeostasis and plant adaptation to adverse conditions. Finally, some plants store VLCFA in the triacylglycerols of their seeds so that they later play a pivotal role in seed germination. In this review, taking advantage of the many studies conducted using Arabidopsis thaliana as a model, we present our current knowledge on the biosynthesis and regulation of VLCFA in plants, and on the various functions that VLCFA and their derivatives play in the interactions of plants with their abiotic and biotic environment

Autophagy

In plants, macroautophagy/autophagy is a key mechanism that contributes to their ability to cope with a wide range of environmental constraints such as drought, nutrient starvation or pathogen resistance. Nevertheless, the molecular mechanisms of plant autophagy, and notably that of autophagosome formation, remain poorly understood. As the starting point of our recent paper, we considered the potential functional contribution of lipids in the numerous membrane-remodeling steps involved in this process. By combining biochemistry, genetics, cell biology and high-resolution 3D imaging, we unraveled the function of the lipid phosphatidylinositol-4-phosphate (PtdIns4P) in autophagy in thus providing novel insights into the assembly of autophagosomes in plant cells.European Union’s Horizon 2020 research and innovation programm

Temperature Acclimation of the Picoalga Ostreococcus tauri Triggers Early Fatty-Acid Variations and Involves a Plastidial ?3-Desaturase

Alteration of fatty-acid unsaturation is a universal response to temperature changes. Marine microalgae display the largest diversity of polyunsaturated fatty-acid (PUFA) whose content notably varies according to temperature. The physiological relevance and the molecular mechanisms underlying these changes are however, still poorly understood. The ancestral green picoalga Ostreococcus tauri displays original lipidic features that combines PUFAs from two distinctive microalgal lineages (Chlorophyceae, Chromista kingdom). In this study, optimized conditions were implemented to unveil early fatty-acid and desaturase transcriptional variations upon chilling and warming. We further functionally characterized the O. tauri ω3-desaturase which is closely related to ω3-desaturases from Chromista species. Our results show that the overall omega-3 to omega-6 ratio is swiftly and reversibly regulated by temperature variations. The proportion of the peculiar 18:5 fatty-acid and temperature are highly and inversely correlated pinpointing the importance of 18:5 temperature-dependent variations across kingdoms. Chilling rapidly and sustainably up-regulated most desaturase genes. Desaturases involved in the regulation of the C18-PUFA pool as well as the Δ5-desaturase appear to be major transcriptional targets. The only ω3-desaturase candidate, related to ω3-desaturases from Chromista species, is localized at chloroplasts in Nicotiana benthamiana and efficiently performs ω3-desaturation of C18-PUFAs in Synechocystis sp. PCC6803. Overexpression in the native host further unveils a broad impact on plastidial and non-plastidial glycerolipids illustrated by the alteration of omega-3/omega-6 ratio in C16-PUFA and VLC-PUFA pools. Global glycerolipid features of the overexpressor recall those of chilling acclimated cells.Développement d'une infrastructure française distribuée pour la métabolomique dédiée à l'innovatio

Isolation and characterization of a cDNA clone (accession no. Y18346) for glutaredoxin from developing tomato fruits

Plant Gene Register pGR 99-001 accès par l'URL : http://www;tarweed.com/pgr/International audienc

Plant Surface Lipids and Epidermis Development

International audienceThe epidermis has a strategic position at the interface between the plant and the environment. In order to control exchanges with the environment as well as to protect the plant from external threats, the epidermis synthesises and secretes surface lipids to form a continuous, transparent and hydrophobic layer known as the cuticle. Cuticle formation is a strictly epidermal property in plants and all aerial epidermal cells produce some sort of cuticle on their surface. Conversely, all cuticularized plant surfaces are of epidermal origin. This seemingly anodyne observation has surprisingly profound implications in terms of understanding the function of the plant cuticle, since it underlies in part, the difficultly of functionally separating epidermal cell fate specification from cuticle biogenesis

Risk factors for liver injury in patients with acquired immunodeficiency syndrome treated with nevirapine

ObjectiveTo investigate the risk factors for hypersensitivity-associated liver injury induced by the combined antiretroviral therapy (c-ART) including nevirapine (NVP) in patients with acquired immunodeficiency syndrome. MethodsThe clinical data and blood samples of 132 patients who received the combined therapy including NVP in Zhongnan Hospital of Wuhan University from June 2008 to October 2015 were collected, and PCR-SSP was used to determine the genotypes of human leukocyte antigen (HLA) DRB1 and HLA-Cw. The patients who experienced hypersensitivity-associated liver injury induced by NVP within 6 weeks of c-ART were enrolled in the liver injury group (41 patients), and those who did not experience liver injury were enrolled in the control group (91 patients). The risk factors for liver injury induced by NVP hypersensitivity were analyzed. The t-test was used for comparison of continuous data between groups; the chi-square test was used for comparison of categorical data between groups. The univariate logistic regression method was used to analyze the risk factors for liver injury associated with NVP hypersensitivity, and the variables with P＜0.10 were included in the multivariate logistic regression model to perform stepwise regression analysis. The Spearman correlation coefficient was used to analyze the correlation between the number of CD4 cells and alanine aminotransferase (ALT) level in patients experiencing hypersensitivity-associated liver injury. ResultsThe results of the multivariate logistic regression analysis showed that male sex (OR=12.297, 95%CI: 2.467-61.300, P=0002), a high CD4 cell count at baseline (OR=1.010, 95%CI: 1.001-1.018, P=0.022), HCV co-infection(OR=10.598, 95%CI: 1.411-79.613, P=0.022), and a HLA-Cw*03 carrier (OR=34.119, 95%CI: 5.543-210.023, P＜0001) were risk factors for liver injury associated with NVP hypersensitivity. In the patients with HCV co-infection or a high CD4 cell count (≥200/μl) or carrying HLA-Cw*03 allele, male patients had a significantly higher incidence rate of liver injury than female patients (63.9% vs 11.6%, χ2=23.390, P＜0.001). Baseline CD4 cell count was positively correlated with ALT level (r=0.583, P＜0001). ConclusionMale patients infected with human immunodeficiency virus who are co-infected with HCV and have a high CD4 cell count at baseline should avoid using NVP. The value of HLA-Cw*03 gene screening in predicting hepatotoxicity associated with NVP hypersensitivity awaits further investigation

Rapid nanoscale quantitative analysis of plant sphingolipid long-chain bases by GC-MS

International audienceIn eukaryotic organisms, sphingolipids are major structural lipids of biological membranes and perform additional essential functions as signalling molecules. While long-chain bases (LCB), the common precursor to all sphingolipid classes, is represented by only one major molecular species in animals and fungi, up to nine LCB have been found in plants. In the absence of genuine plant sphingolipid references required for proper quantification, we have reinvestigated and optimized a protocol destined to the quantification of total plant LCB that relies on the use of gas chromatography-mass spectrometry (GC-MS). This rapid three-step protocol sequentially involves (1) the release of LCB from biological samples using barium hydroxide solution, (2) their oxidation into aldehydes by metaperiodate, and (3) the subsequent identification/quantification of these aldehydes by GC-MS. It is simple and reliable and enables separation of aldehydes upon their stero-specificity. It further enables the quantification of total LCB from a wide variety of samples including yeast and animal cell culturesIn eukaryotic organisms, sphingolipids are major structural lipids of biological membranes and perform additional essential functions as signalling molecules. While long-chain bases (LCB), the common precursor to all sphingolipid classes, is represented by only one major molecular species in animals and fungi, up to nine LCB have been found in plants. In the absence of genuine plant sphingolipid references required for proper quantification, we have reinvestigated and optimized a protocol destined to the quantification of total plant LCB that relies on the use of gas chromatography-mass spectrometry (GC-MS). This rapid three-step protocol sequentially involves (1) the release of LCB from biological samples using barium hydroxide solution, (2) their oxidation into aldehydes by metaperiodate, and (3) the subsequent identification/quantification of these aldehydes by GC-MS. It is simple and reliable and enables separation of aldehydes upon their stero-specificity. It further enables the quantification of total LCB from a wide variety of samples including yeast and animal cell culture

A new C-type Cyclin-dependent kinase from tomato expressed in dividing tissues does not interact with motic and G1 cyclins

International audienc

Rapid growth in tomato fruit : cytological, molecular and metabolic approaches

National audienc