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Exploring and deciphering the biodiversity of oil bodies (OBs) recovered from oilseeds are of growing interest in the preparation of sustainable, natural and healthy plant-based food products. This study focused on chia (Salvia hispanica L.) and camelina (Camelina sativa L.) seed OBs. A green refinery process including ultrasound to remove mucilage, aqueous extraction by grinding and centrifugation to recover OBs from the seeds was used. The microstructure, composition and physical stability of the OBs were examined. Confocal laser scanning microscopy images showed that chia and camelina seed OBs are spherical assemblies coated by a layer of phospholipids and proteins, which have been identified by gel electrophoresis. The mean diameters determined by laser light scattering measurements were 2.3 and 1.6 µm for chia and camelina seed OBs, respectively. The chia and camelina seed OBs were rich in lipids and other bioactive components with, respectively, 64% and 30% α-linolenic acid representing 70% and 53% of the total fatty acids in the sn-2 position of the triacylglycerols, 0.23% and 0.26% phospholipids, 3069 and 2674 mg/kg oil of β-sitosterol, and lipophilic antioxidants: 400 and 670 mg/kg oil of γ-tocopherol. Phenolic compounds were recovered from the aqueous extracts, such as rutin from camelina and caffeic acid from chia. Zeta-potential measurements showed changes from about −40 mV (pH 9) to values that were positive below the isoelectric points of pH 5.1 and 3.6 for chia and camelina seed OBs, respectively. Below pH 6.5, physical instability of the natural oil-in-water emulsions with aggregation and phase separation was found. This study will contribute to the development of innovative and sustainable food products based on natural oil-in-water emulsions containing chia and camelina seed OBs for their nutritional and health benefits.

Hepatocyte invasion by Plasmodium sporozoites represents a promising target for innovative antimalarial therapy, but the molecular events mediating this process are still largely uncharacterized. We previously showed that Plasmodium falciparum sporozoite entry into hepatocytes strictly requires CD81. However, CD81-overexpressing human hepatoma cells remain refractory to P. falciparum infection, suggesting the existence of additional host factors necessary for sporozoite entry. Here, through differential transcriptomic analysis of human hepatocytes and hepatoma HepG2-CD81 cells, the transmembrane protein Aquaporin-9 (AQP9) was found to be among the most downregulated genes in hepatoma cells. RNA silencing showed that sporozoite invasion of hepatocytes requires AQP9 expression. AQP9 overexpression in hepatocytes increased their permissiveness to P. falciparum. Moreover, chemical disruption with the AQP9 inhibitor phloretin markedly inhibited hepatocyte infection. Our findings identify AQP9 as a novel host factor required for P. falciparum sporozoite hepatocyte-entry and indicate that AQP9 could be a potential therapeutic target.

It has now been clearly shown that lipid droplets (LDs) play a dynamic role in the cell. This was reinforced by LD proteomics which suggest that a significant number of trafficking proteins are associated with this organelle. Using microscopy, we showed that LDs partly co-localize with the vacuole in S. cerevisiae. Immunoblot experiments confirmed the association of the vacuolar Rab GTPase Rab7-like Ypt7p with LDs. We observed an increase in fatty acid content and LD number in ypt7Δ mutant and also changes in LD morphology and intra LD fusions, revealing a direct role for Ypt7p in LD dynamics. Using co-immunoprecipitation, we isolated potential Ypt7p partners including, Vma13p, the H subunit of the V1 part of the vacuolar (H+) ATPase (V-ATPase). Deletion of the VMA13 gene, as well as deletion of three other subunits of the V1 part of the V-ATPase, also increased the cell fatty acid content and LD number. Mutants of the Homotypic fusion and vacuole protein sorting (HOPS) complex showed similar phenotypes. Here, we demonstrated that LD dynamics and membrane trafficking between the vacuole and LDs are regulated by the Rab7-like Ypt7p and are impaired when the HOPS complex and the V1 domain of the V-ATPase are defective.

Two lignocellulosic agricultural residues, sunflower stalks and rape straw, were investigated as potential low-cost, non-food substrates for the production of triacylglycerols by the oleaginous, lignocellulolytic bacteria Streptomyces lividans. Chemical analysis of each type of residue revealed similar cell wall compositions in the polysaccharides and lignins of the two feedstocks, with high lignin β-O-4 bond content compared to other angiosperms’ lignin. Growing tests of Streptomyces lividans TK 24 were performed before and after sequential water and ethanol extraction by assessing bacterial fatty acid accumulation. All extracted and non-extracted samples were found to be substrates of the bacteria with fatty acid production ranging between 19% and 44% of the production obtained with arabinose as a reference substrate. The maximum conversion rate was obtained with the less lignified, non-extracted sample. This study suggests that lignocellulosic residues from oleaginous crops could be advantageously valorized by microbial bioconversion processes for the production of lipids of interest.

A long term data acquisition effort of profile soil moisture is under way in southwestern France at 13 automated weather stations. This ground network was developed in order to validate remote sensing and model soil moisture estimates. In this paper, both those in situ observations and a synthetic data set covering continental France are used to test a simple method to retrieve root zone soil moisture from a time series of surface soil moisture information. A recursive exponential filter equation using a time constant, T, is used to compute a soil water index. The Nash and Sutcliff coefficient is used as a criterion to optimise the T parameter for each ground station and for each model pixel of the synthetic data set. In general, the soil water indices derived from the surface soil moisture observations and simulations agree well with the reference root-zone soil moisture. Overall, the results show the potential of the exponential filter equation and of its recursive formulation to derive a soil water index from surface soil moisture estimates. This paper further investigates the correlation of the time scale parameter T with soil properties and climate conditions. While no significant relationship could be determined between T and the main soil properties (clay and sand fractions, bulk density and organic matter content), the modelled spatial variability and the observed inter-annual variability of T suggest that a weak climate effect may exist.

In most organisms, storage lipids are packaged into specialized structures called lipid droplets. These contain a core of neutral lipids surrounded by a monolayer of phospholipids, and various proteins which vary depending on the species. Hydrophobic structural proteins stabilize the interface between the lipid core and aqueous cellular environment (perilipin family of proteins, apolipoproteins, oleosins). We developed a genetic approach using heterologous expression in Saccharomyces cerevisiae of the Arabidopsis thaliana lipid droplet oleosin and caleosin proteins AtOle1 and AtClo1. These transformed yeasts overaccumulate lipid droplets, leading to a specific increase in storage lipids. The phenotype of these cells was explored using synchrotron FT-IR microspectroscopy to investigate the dynamics of lipid storage and cellular carbon fluxes reflected as changes in spectral fingerprints. Multivariate statistical analysis of the data showed a clear effect on storage carbohydrates and more specifically, a decrease in glycogen in our modified strains. These observations were confirmed by biochemical quantification of the storage carbohydrates glycogen and trehalose. Our results demonstrate that neutral lipid and storage carbohydrate fluxes are tightly connected and co-regulated.

Oil from oleaginous seeds is mainly composed of triacylglycerols. Very long chain fatty acids (VLCFAs) are major constituents of triacylglycerols in many seed oils and represent valuable feedstock for industrial purposes. To identify genetic factors governing natural variability in VLCFA biosynthesis, a quantitative trait loci (QTL) analysis using a recombinant inbred line population derived from a cross between accessions Bay-0 and Shahdara was performed in Arabidopsis thaliana. Two fatty acid chain length ratio (CLR) QTL were identified, with one major locus, CLR.2, accounting for 77% of the observed phenotypic variation. A fine mapping and candidate gene approach showed that a key enzyme of the fatty acid elongation pathway, the β-ketoacyl-CoA synthase 18 (KCS18), was responsible for the CLR.2 QTL detected between Bay-0 and Shahdara. Association genetics and heterologous expression in yeast cells identified a single point mutation associated with an alteration of KCS18 activity, uncovering the molecular bases for the modulation of VLCFA content in these two natural populations of Arabidopsis. Identification of this kcs18 mutant with altered activity opens new perspectives for the modulation of oil composition in crop plants.

Plasmodium sporozoites are deposited in the skin by Anopheles mosquitoes. They then find their way to the liver, where they specifically invade hepatocytes in which they develop to yield merozoites infective to red blood cells. Relatively little is known of the molecular interactions during these initial obligatory phases of the infection. Recent data suggested that many of the inoculated sporozoites invade hepatocytes an hour or more after the infective bite. We hypothesised that this pre-invasive period in the mammalian host prepares sporozoites for successful hepatocyte infection. Therefore, the genes whose expression becomes modified prior to hepatocyte invasion would be those likely to code for proteins implicated in the subsequent events of invasion and development. We have used P. falciparum sporozoites and their natural host cells, primary human hepatocytes, in in vitro co-culture system as a model for the pre-invasive period. We first established that under co-culture conditions, sporozoites maintain infectivity for an hour or more, in contrast to a drastic loss in infectivity when hepatocytes were not included. Thus, a differential transcriptome of salivary gland sporozoites versus sporozoites co-cultured with hepatocytes was established using a pan-genomic P. falciparum microarray. The expression of 532 genes was found to have been up-regulated following co-culture. A fifth of these genes had no orthologues in the genomes of Plasmodium species used in rodent models of malaria. Quantitative RT-PCR analysis of a selection of 21 genes confirmed the reliability of the microarray data. Time-course analysis further indicated two patterns of up-regulation following sporozoite co-culture, one transient and the other sustained, suggesting roles in hepatocyte invasion and liver stage development, respectively. This was supported by functional studies of four hitherto uncharacterized proteins of which two were shown to be sporozoite surface proteins involved in hepatocyte invasion, while the other two were predominantly expressed during hepatic parasite development. The genome-wide up-regulation of expression observed supports the hypothesis that the shift from the mosquito to the mammalian host contributes to activate quiescent salivary gland sporozoites into a state of readiness for the hepatic stages. Functional studies on four of the up-regulated genes validated our approach as one means to determine the repertoire of proteins implicated during the early events of the Plasmodium infection, and in this case that of P. falciparum, the species responsible for the severest forms of malaria.

Invasion of hepatocytes by Plasmodium sporozoites is a prerequisite for establishment of a malaria infection, and thus represents an attractive target for anti-malarial interventions. Still, the molecular mechanisms underlying sporozoite invasion are largely unknown. We have previously reported that the tetraspanin CD81, a known receptor for the hepatitis C virus (HCV), is required on hepatocytes for infection by sporozoites of several Plasmodium species. Here we have characterized CD81 molecular determinants required for infection of hepatocytic cells by P. yoelii sporozoites. Using CD9/CD81 chimeras, we have identified in CD81 a 21 amino acid stretch located in a domain structurally conserved in the large extracellular loop of tetraspanins, which is sufficient in an otherwise CD9 background to confer susceptibility to P. yoelii infection. By site-directed mutagenesis, we have demonstrated the key role of a solvent-exposed region around residue D137 within this domain. A mAb that requires this region for optimal binding did not block infection, in contrast to other CD81 mAbs. This study has uncovered a new functionally important region of CD81, independent of HCV E2 envelope protein binding domain, and further suggests that CD81 may not interact directly with a parasite ligand during Plasmodium infection, but instead may regulate the function of a yet unknown partner protein.

Summary: Infection of hepatocytes by Plasmodium falciparum sporozoites requires the host tetraspanin CD81. CD81 is also predicted to be a coreceptor, along with scavenger receptor BI (SR-BI), for hepatitis C virus. Using SR-BI-knockout, SR-BI-hypomorphic and SR-BI-transgenic primary hepatocytes, as well as specific SR-BI-blocking antibodies, we demonstrate that SR-BI significantly boosts hepatocyte permissiveness to P. falciparum, P. yoelii, and P. berghei entry and promotes parasite development. We show that SR-BI, but not the low-density lipoprotein receptor, acts as a major cholesterol provider that enhances Plasmodium infection. SR-BI regulates the organization of CD81 at the plasma membrane, mediating an arrangement that is highly permissive to penetration by sporozoites. Concomitantly, SR-BI upregulates the expression of the liver fatty-acid carrier L-FABP, a protein implicated in Plasmodium liver-stage maturation. These findings establish the mechanistic basis of the CD81-dependent Plasmodium sporozoite invasion pathway. [Copyright &y& Elsevier]