Structural features conferring dual Geranyl/Farnesyl diphosphate synthase activity to an aphid prenyltransferase

in Insect Biochemistry and Molecular Biology (2009), 39(10), 707-716

In addition to providing lipid chains for protein prenylation, short-chain isoprenyl diphosphate synthases (scIPPSs) play a pivotal role in the biosynthesis of numerous mevalonate pathway end-products ... [more ▼]

In addition to providing lipid chains for protein prenylation, short-chain isoprenyl diphosphate synthases (scIPPSs) play a pivotal role in the biosynthesis of numerous mevalonate pathway end-products, including insect juvenile hormone and terpenoid pheromones. For this reason, they are being considered as targets for pesticide development. Recently, we characterized an aphid scIPPS displaying dual geranyl diphosphate (GPP; C10)/farnesyl diphosphate (FPP; C15) synthase activity in vitro. To identify the mechanism(s) responsible for this dual activity, we assessed the product selectivity of aphid scIPPSs bearing mutations at Gln107 and/or Leu110, the fourth and first residue upstream from the “first aspartate-rich motif” (FARM), respectively. All but one resulted in significant changes in product chain-length selectivity, effectively increasing the production of either GPP (Q107E, L110W) or FPP (Q107F, Q107F–L110A); the other mutation (L110A) abolished activity. Although some of these effects could be attributed to changes in steric hindrance within the catalytic cavity, molecular dynamics simulations identified other contributing factors, including residue-ligand Van der Waals interactions and the formation of hydrogen bonds or salt bridges between Gln107 and other residues across the catalytic cavity, which constitutes a novel product chain-length determination mechanism for scIPPSs. Thus the aphid enzyme apparently evolved to maintain the capacity to produce both GPP and FPP through a balance between these mechanisms. [less ▲]

Mise en relation de la diversité des vers de terre et des caractéristiques du sol de Thua Thien Hue (Centre Vietnam)

in Tropical Conservation Science (2009), 2(3), 282-298

The large proportion of sandy soils of Thua Thien Hue, in Central Vietnam, present a particular habitat for soil-inhabiting organisms among which earthworms represent close to 70% of total biomass. This ... [more ▼]

The large proportion of sandy soils of Thua Thien Hue, in Central Vietnam, present a particular habitat for soil-inhabiting organisms among which earthworms represent close to 70% of total biomass. This study identified relationships between the characteristics of soil and earthworms. Our inventories yielded the presence of seven species of earthworms belonging to the families Glossoscolecidae, Megascolecidae and Microchaetidae. These were: Pontoscolex corethrurus, Glyphidrilus papillatus, Pheretima rodericensis, Pheretima danangana, Pheretima sp., Perionyx excavatus, and Lampito mauritii. Those of the Microchaetidae were present in acid soils with a high rate of silt and clay. Species in the other families were associated with poor but less acid sandy soils. This study also showed that the number of P. corethrurus was significantly higher in orchards while L. mauritii was significantly more common in soils with cultures other than rice. The species G. papillatus was significantly more abundant in fallow and was the only species found in this habitat. Highest earthworm diversity (Shannon-Wiener index(H=0.97)) was found in crops like manioc and sweat potatoes rather than in rice. [less ▲]

Attacks by a piercing-sucking insect (Myzus persicae Sultzer) or a chewing insect (Leptinotarsa decemlineata Say) on potato plants (Solanum tuberosum L.) induce differential changes in volatile compound release and oxylipin synthesis

in Journal of Experimental Botany (2009), 60(4), 1231-1240

Plant defensive strategies bring into play blends of compounds dependent on the type of attacker and coming from different synthesis pathways. Interest in the field is mainly focused on volatile organic ... [more ▼]

Plant defensive strategies bring into play blends of compounds dependent on the type of attacker and coming from different synthesis pathways. Interest in the field is mainly focused on volatile organic compounds (VOCs) and jasmonic acid (JA). By contrast, little is known about the oxidized polyunsaturated fatty acids (PUFAs), such as PUFA-hydroperoxides, PUFA-hydroxides, or PUFA-ketones. PUFA-hydroperoxides and their derivatives might be involved in stress response and show antimicrobial activities. Hydroperoxides are also precursors of JA and some volatile compounds. In this paper, the differential biochemical response of a plant against insects with distinct feeding behaviours is characterized not only in terms of VOC signature and JA profile but also in terms of their precursors synthesized through the lipoxygenase (LOX)-pathway at the early stage of the plant response. For this purpose, two leading pests of potato with distinct feeding behaviours were used: the Colorado Potato Beetle (Leptinotarsa decemlineata Say), a chewing herbivore, and the Green Peach Aphid (Myzus persicae Sulzer), a piercing-sucking insect. The volatile signatures identified clearly differ in function with the feeding behaviour of the attacker and the aphid, which causes the smaller damages, triggers the emission of a higher number of volatiles. In addition, 9-LOX products, which are usually associated with defence against pathogens, were exclusively activated by aphid attack. Furthermore, a correlation between volatiles and JA accumulation and the evolution of their precursors was determined. Finally, the role of the insect itself on the plant response after insect infestation was highlighted. [less ▲]

Physicochemical Characteristics of Date Sap Lagmi from Deglet Nour Palm (Phoenix Dactylifera L.)

in International Journal of Food Properties (2009), 12(3), 659-670

Physicochemical properties of sap from Deglet Nour date palm (Phoenix dactylifera L.) were studied. Composition analysis revealed (on a dry-weight basis) a high content of carbohydrates (94.98 g/100 g of ... [more ▼]

Physicochemical properties of sap from Deglet Nour date palm (Phoenix dactylifera L.) were studied. Composition analysis revealed (on a dry-weight basis) a high content of carbohydrates (94.98 g/100 g of dry matter basis) mainly sucrose, 2.72 g/100g (dry matter basis) of proteins and 2.29 g/100 g (dry matter basis) of ash. Date palm sap also contains 7.64 mg gallic acid equivalent/100 ml of total polyphenol. Thus, date palm sap showed antioxidant activity with a percentage inhibition of the DPPH radical value of 47.64%. Surface and foaming properties were also performed by drop volume and bubbling method, respectively. Equilibrium surface tension of fresh sap was 63.51 mN/m. Freeze-drying method preserved surface activity. Native sap showed better foam power (1.03) and foam stability (1150 s) than solutions prepared from lyophilised sap (5-30 g /100g of solution). Results demonstrated that this natural juice could be regarded as functional food due to its high nutritional value, antioxidant activity, surface activity, and foam power. [less ▲]

Farming systems in the sandy area of the Thua Thien Hue Province, Central Vietnam, survey of socio-economic situation and constraints identified by farmers

in Improving food crop productivity in the coastal sandy area of the Thua Thien Hue Province Central Vietnam : Vietnam-Belgium interuniversity project 2004-2009 (2009)

Effect of stinging nettle habitats on aphidophagous predators and parasitoids in wheat and green pea fields with particular attention to the invader Harmonia axyridis (Coleoptera: Coccinellidae)

in Entomological Science (2009), 12

La membrane du globule gras du lait (MFGM) : une composition et une structure originale.

Poster (2008, January 23)

Breeding Sites Of Bluetongue Vectors In Northern Europe

in Veterinary Record : Journal of the British Veterinary Association (2008), 162(4), 131

Proteome analysis of the bovine milk fat globule: Enhancement of membrane purification

in International Dairy Journal (2008), 18(9), 885-893

A simple and rapid procedure was cl developed for the extraction of the milk fat globule membrane from milk removes the large majority of the skim milk proteins for proteome analysis. In order to improve ... [more ▼]

A simple and rapid procedure was cl developed for the extraction of the milk fat globule membrane from milk removes the large majority of the skim milk proteins for proteome analysis. In order to improve the extraction and the solubilization of the hydrophobic membrane proteins for subsequent two-dimensional gel electrophoresis, four detergents (3-[(3-cholamidopropyl)dimethylammoniol-1-propanesulfonate, amidosulfobetaine-14, sodium lauroyl sarcosinate and sodium deoxycholate) were tested in the sample preparation, associated with a sonication step. Zwitterionic detergents were shown to be efficient in recovering integral and peripheral proteins from membrane material. Spots were identified by matrix-assisted laser desorption/ionization tandem-time-of-flight (MALDI-TOF/TOF). The advantages of MALDI-TOF/TOF (speed, easiness of analysis, good sensitivity and high mass accuracy) were demonstrated on the milk fat globule membrane proteome investigation. Identified proteins are implicated in a wide range of functions including fat secretion and transport, protein trafficking and regulation. (C) 2008 Elsevier Ltd. All rights reserved. [less ▲]

Characterization of a novel aphid prenyltransferase displaying dual geranyl/farnesyl diphosphate synthase activity

in FEBS Letters (2008), 582(16), 19281934

We report on the cDNA cloning and characterization of a novel short-chain isoprenyl diphosphate synthase from the aphid Myzus persicae. Of the three IPPS cDNAs we cloned, two yielded prenyltransferase ... [more ▼]

We report on the cDNA cloning and characterization of a novel short-chain isoprenyl diphosphate synthase from the aphid Myzus persicae. Of the three IPPS cDNAs we cloned, two yielded prenyltransferase activity following expression in Escherichia coli; these cDNAs encode identical proteins except for the presence, in one of them, of an N-terminal mitochondrial targeting peptide. Although the aphid enzyme was predicted to be a farnesyl diphosphate synthase by BLASTP analysis, rMpIPPS, when isopentenyl diphosphate and dimethylallyl diphosphate are supplied as substrates, typically generated geranyl diphosphate (C10) as its main product, along with significant quantities of farnesyl diphosphate (C15). Analysis of an MpIPPS homology model pointed to substitutions that could confer GPP/FPP synthase activity to the aphid enzyme. [less ▲]