Paul-Henri Ducrot

IDENTIFICATION AND SYNTHESIS OF SORDIDIN, A MALE PHEROMONE EMITTED BY COSMOPOLITES SORDIDUS

Abstract The diastereoselective synthesis of (1S∗, 3R∗, 5R∗, 7S∗) 2,8-dioxa 1-ethyl 3,5,7-trimethyl bicylo [3,2,1] octane 1d has been achieved using as key-step the regioselective Baeyer-Villiger reaction of 2,6-disubstituted cyclohexanone. It confirms the identification of a new male pheromone emitted by the banana weevil, Cosmopolites sordidus. The trivial name sordidin is proposed.

Imbalanced lignin biosynthesis promotes the sexual reproduction of homothallic oomycete pathogens.

Lignin is incorporated into plant cell walls to maintain plant architecture and to ensure long-distance water transport. Lignin composition affects the industrial value of plant material for forage, wood and paper production, and biofuel technologies. Industrial demands have resulted in an increase in the use of genetic engineering to modify lignified plant cell wall composition. However, the interaction of the resulting plants with the environment must be analyzed carefully to ensure that there are no undesirable side effects of lignin modification. We show here that Arabidopsis thaliana mutants with impaired 5-hydroxyguaiacyl O-methyltransferase (known as caffeate O-methyltransferase; COMT) function were more susceptible to various bacterial and fungal pathogens. Unexpectedly, asexual sporulation of the downy mildew pathogen, Hyaloperonospora arabidopsidis, was impaired on these mutants. Enhanced resistance to downy mildew was not correlated with increased plant defense responses in comt1 mutants but coincided with a higher frequency of oomycete sexual reproduction within mutant tissues. Comt1 mutants but not wild-type Arabidopsis accumulated soluble 2-O-5-hydroxyferuloyl-l-malate. The compound weakened mycelium vigor and promoted sexual oomycete reproduction when applied to a homothallic oomycete in vitro. These findings suggested that the accumulation of 2-O-5-hydroxyferuloyl-l-malate accounted for the observed comt1 mutant phenotypes during the interaction with H. arabidopsidis. Taken together, our study shows that an artificial downregulation of COMT can drastically alter the interaction of a plant with the biotic environment.

A functional bikaverin biosynthesis gene cluster in rare strains of Botrytis cinerea is positively controlled by VELVET.

The gene cluster responsible for the biosynthesis of the red polyketidic pigment bikaverin has only been characterized in Fusarium ssp. so far. Recently, a highly homologous but incomplete and nonfunctional bikaverin cluster has been found in the genome of the unrelated phytopathogenic fungus Botrytis cinerea. In this study, we provided evidence that rare B. cinerea strains such as 1750 have a complete and functional cluster comprising the six genes orthologous to Fusarium fujikuroi ffbik1-ffbik6 and do produce bikaverin. Phylogenetic analysis confirmed that the whole cluster was acquired from Fusarium through a horizontal gene transfer (HGT). In the bikaverin-nonproducing strain B05.10, the genes encoding bikaverin biosynthesis enzymes are nonfunctional due to deleterious mutations (bcbik2-3) or missing (bcbik1) but interestingly, the genes encoding the regulatory proteins BcBIK4 and BcBIK5 do not harbor deleterious mutations which suggests that they may still be functional. Heterologous complementation of the F. fujikuroi Δffbik4 mutant confirmed that bcbik4 of strain B05.10 is indeed fully functional. Deletion of bcvel1 in the pink strain 1750 resulted in loss of bikaverin and overproduction of melanin indicating that the VELVET protein BcVEL1 regulates the biosynthesis of the two pigments in an opposite manner. Although strain 1750 itself expresses a truncated BcVEL1 protein (100 instead of 575 aa) that is nonfunctional with regard to sclerotia formation, virulence and oxalic acid formation, it is sufficient to regulate pigment biosynthesis (bikaverin and melanin) and fenhexamid HydR2 type of resistance. Finally, a genetic cross between strain 1750 and a bikaverin-nonproducing strain sensitive to fenhexamid revealed that the functional bikaverin cluster is genetically linked to the HydR2 locus.

Chemo-enzymatic preparation of new bio-based bis- and trisphenols: new versatile building blocks for polymer chemistry

Immobilized Candida antartica lipase B (aka CAL-B) was used to perform solvent-free and in solvent transesterifications of a derivative from ferulic acid (1), ethyl dihydroferulate (2), with various bio-based polyols (isosorbide, 1,3-propanediol, 1,4-butanediol and glycerol). The use of 1.5 molar eq of ethyl dihydroferulate (2) per alcohol functionality and CAL-B (10% by weight relative to the total weight of polyol and 2) led to the corresponding poly-ferulates (3–6) in very good yields and high purity. These poly-ferulates were then efficiently transformed through one-step processes into the corresponding acrylates (7–10) and allyl ethers (11–14) to demonstrate their potential use as biorenewable macromonomers in a wide range of polymerization systems.

Oligomeric compounds formed from 2,5-xylidine (2,5-dimethylaniline) are potent enhancers of laccase production in Trametes versicolor ATCC 32745

Numerous chemicals, including the xenobiotic 2,5-xylidine, are known to induce laccase production in fungi. The present study was conducted to determine whether the metabolites formed from 2,5-xylidine by fungi could enhance laccase activity. We used purified laccases to transform the chemical and then we separated the metabolites, identified their chemical structure and assayed their effect on enzyme activity in liquid cultures of Trametes. versicolor. We identified 13 oligomers formed from 2,5-xylidine. (4E)-4-(2,5-dimethylphenylimino)-2,5-dimethylcyclohexa-2,5-dienone at 1.25×10−5 M was an efficient inducer, resulting in a nine-fold increase of laccase activity after 3 days of culture. Easily synthesized in one step (67% yield), this compound could be used in fungal bioreactors to obtain a great amount of laccases for biochemical or biotechnological purposes, with a low amount of inducer.

Chemical identification, electrophysiological and behavioral activities of the pheromone of Metamasius hemipterus (Coleoptera: Curculionidae).

Five hydroxylated aliphatic molecules were identified as the pheromone produced by male West Indian Sugarcane Borer (WISB): 4-methyl-5-nonanol (1), 2-methyl-4-heptanol (2), 2-methyl-4-octanol (3), 5-nonanol (4) and 3-hydroxy-4-methyl-5-nonanone (5). Electroantennographic recordings revealed antennal responses to compounds 1, 2, 3 and 4. Significant EAGs were also recorded in response to pheromone compounds of weevils belonging to the same subfamily and structurally related to the WISB pheromone. The natural pheromone elicited aggregation behavior on WISB adults in laboratory bioassays.

Dorsal abdominal glands in nymphs of southern green stink bug,Nezara viridula (L.) (heteroptera: Pentatomidae): Chemistry of secretions of five instars and role of (E)-4-oxo-2-decenal, compound specific to first instars

We investigated the exocrine secretions from the five nymphal instars in the southern green stink bug,Nezara viridula, by analyzing separately the contents of the three dorsal abdominal reservoirs. All DAGs 1 produced a mixture of five alkanes with 12, 13, 14, 15, and 16 carbons. No differences were found between DAGs 2 and DAGs 3, for the five instars: the glands of first instars produce the same alkanes as DAGs 1,n-tridecane, traces of (E)-2-decenal, and a specific compound: (E)-4-oxo-2-decenal. In the other instars (second to fifth), (E)-4-oxo-2-decenal is absent from the secretion but another compound is present: (E)-4-oxo-2-hexenal. The kinetics of production of the different compounds were studied, the maximum amounts produced occurring 36 hr after hatching. The biological function of (E)-4-oxo-2-decenal was investigated. Using olfactometry, we showed that this compound acts as an attractant and an arrestant on second instars, at physiological doses. Moreover, this semiochemical was shown to be repellent to the fire-antSolenopsis geminata, a potential predator ofN. viridula and we established the dose-response curve for the repellent activity.

Cyphostemmins A-B, two new antifungal oligostilbenes from Cyphostemma crotalarioides (Vitaceae)

Abstract Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and 1H and 13C NMR spectroscopic data.

Synthesis of agarofuran antifeedants. Part 6: Enantioselective synthesis of a key decalinic intermediate

The asymmetric synthesis of a template decalin precursor in the synthesis of polyhydroxylated agarofuran sesquiterpenes is described via a Lewis acid catalysed addition of furan to an activated cyclohexenone directed by an adjacent chiral ketal moiety.

On the regioselectivity of the Baeyer-Villiger reaction of 2,6-dialkyl cyclohexanones: Application to the synthesis of sordidin, a male pheromone emitted by Cosmopolites sordidus

Abstract The diastereoselective synthesis of (1S ∗ ,3R ∗ ,5R ∗ ,7S ∗ )-2,8- dioxa-1-ethyl-3,5,7-trimethylbicyclo[3.2.1]octane ( 1d ) has been achieved using as the key step the regioselective Baeyer-Villiger reaction of 2,6-disubstituted cyclohexanone.