Didier Delay

Productivity, water-use efficiency and tolerance to moderate water deficit correlate in 33 poplar genotypes from a Populus deltoides × Populus trichocarpa F1 progeny

Genotypic variability for productivity, water-use efficiency and leaf traits in 33 genotypes selected from an F1 progeny of Populus deltoides Bartr. ex Marsh x Populus trichocarpa L. was explored under optimal and moderate water-deficit conditions. Saplings of the 33 genotypes were grown in a two-plot open field at INRA Orléans (France) and coppiced every year. A moderate water deficit was induced during two successive years on one plot by withholding irrigation, while the second one remained irrigated (control). Stem biomass and leaf structure (e.g., specific leaf area and leaf area) were measured in 2004 and 2005 and functional leaf traits (e.g., carbon isotope discrimination, Delta) were measured only in 2004. Tolerance to water deficit was estimated at genotype level as the ability to limit losses in biomass production in water deficit versus control trees. Stem biomass, leaf structure and Delta displayed a significant genotypic variability whatever the irrigation regime. For all traits, genotype ranks remained stable across years for similar irrigation conditions. Carbon isotope discrimination scaled negatively with productivity and leaf nitrogen content in controls. The most productive genotypes were the least tolerant to moderate water deficit. No relationship was evidenced between Delta and the level of tolerance to water deficit. The relationships between traits evidenced in this collection of P. deltoides x P. trichocarpa F1 genotypes contrast with the ones that were previously detected in a collection of P. deltoides x Populus nigra L. cultivars tested in the same field trial.

Alkylsyringamides, new inducers of Agrobacterium tumefaciens virulence genes

The virulence genes of Agrobacterium tumefaciens are specifically activated by plant phenolic compounds and allow this organism to genetically transform plant cells. New types of phenolic compounds, three phenol amides derived from syringic acid, were synthesized. Introduction of an amide group in syringic acid strongly enhances its vir gene inducing activity.

New syntheses of plant aryl glycosides as potential gene inducers

Abstract Aryl β- d -glycopyranosides have been synthesized by coupling acetovanillone (4-hydroxy-3-methoxyacetophenone) with d -glucose, d -galactose, and maltose; acetosyringone (4-hydroxy-3,5-dimethoxyacetophenone) with d -glucose and d -galactose; syringaldehyde (3-methoxyvanillin) with d -glucose; and syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid) with d -glucose. The Mauthners procedure using peracetylated glycosyl bromides and phenolates in aqueous acetone afforded the acetylated β- d -glycosides, which were deacetylated.

Synthesis and Agrobacterium vir-inducing activities of coniferyl alcohol β-glycosides

Abstract Coniferyl alcohol β-glycosides were synthesized by coupling coniferyl alcohol sodium salt in aqueous acetone with peracetylated glycosyl halides of d -glucopyranose, d -galactopyranose and l -fucopyranose. After O -deacetylation by sodium methoxide, the glycosides were tested for their potential vir gene-inducing activities in Agrobacterium tumefaciens A348/pSM358 and A348/pSM243cd harbouring, respectively, virE::lacZ and virB::lacZ fusion plasmids. In the large range of concentrations tested, these synthetic derivatives had vir -inducing activity on strain A348/pSM358: d -Gal > d -Glc. The dose-response curves of these glycosylated compounds were completely different from those of free coniferyl alcohol; the β-galactopyranoside at 500,μM exhibited interestingly a greater activity than the free aglycone after a 12 hr incubation period. The coniferyl alcohol β-glucopyranoside was a better inducer than the related β-galactopyranoside on strain A348/pSM243cd. The β- l -fucopyranoside was inactive with both A. tumefaciens strains. The activities of these glycosylated inducers were correlated with the presence of intracellular glycosylhydrolases from the various A. tumefaciens strains studied. It is noteworthy that the vir -gene induction activity of the coniferyl alcohol β-galactopyranoside on strain A348/pSM358 was due to a high basal level of expression of the virE::lacZ fusion gene.

Agrobacterium vir-inducing activities of glycosylated acetosyringone, acetovanillone, syringaldehyde and syringic acid derivatives

Abstract Expression of the Agrobacterium tumefaciens virulence ( vir ) gene is known to be dependent on host plant phenolic compounds. The A. tumefaciens strain A348 (pSM358) harbouring a vir E:: lac Z fusion plasmid was used to detect the ability of 13 synthetic acetosyringone, acetovanillone, syringaldehyde and syringic acid β-glycosides to induce virulence. The activity of the reporter β-galactosidase was detected by spectrofluorimetry using 4-methylumbelliferyl β-galactopyranoside as substrate. Acetosyringonyl β- l -fucopyranoside was the most active monoglycoside tested; even at high concentration this compound was devoid of toxic effects. However, monoglycosides were less active vir inducers than free acetosyringone. In contrast, the β-maltoside of syringaldehyde showed higher activity than the free phenol at high concentration. The activity of such glycosylated inducers may be related to specific sugar receptors on the bacterial cell surface.

vir-Gene-inducing activities of hydroxycinnamic acid amides in Agrobacterium tumefaciens

Expression of Agrobacterium tumefaciens virulence genes and transformation of dicots by this organism are dependent upon host plant phenolic compounds. Several alkylsyringamides have recently been shown to be powerful inducers of these vir-genes. These synthetic amides, and especially ethylsyringamide, are much stronger inducers than syringic acid. In this work, four alkylamides derived from ferulic or sinapic acids were synthesized by a dicyclohexylcarbodiimide method and tested for their potential to induce vir-gene expression on A. tumefaciens strains harbouring virB::lacZ or virE::lacZ fusion plasmids. Their effectiveness was compared to that of ethylsyringamide and tyraminylferulamide, a naturally occurring amide in plants. Whatever the amine moiety of the amide (ethylamine, propylamine, tyramine or beta-alanine ethyl ester) conjugation of the acid functional group clearly diminished the toxicity to the bacteria of the respective acid at high concentration and thereby increased the vir-inducing potential. However, none of the inducers tested exhibited higher activity than acetosyringone, the reference compound for vir-gene induction, with the exception of ethylsyringamide at concentrations above 1mM. When tested on Agrobacterium tumefaciens strain A348(pSM243cd), ethylferulamide and ethylsinapamide were more efficient than the corresponding phenolic acids but only above 100 microM.

Synthesis of aryl glycosides as vir gene inducers of Agrobacterium tumefaciens

Abstract Aryl β-glycopyranosides have been synthesized by coupling syringaldehyde (3-methoxyvanillin) with l -fucose, d -galactose, and maltose; acetosyringone (4-hydroxy-3,5-dimethoxyacetophenone) with l -fucose and maltose; acetovanillone (4-hydroxy-3-methoxyacetophenone) with l -fucose; and syringic acid (4-hydroxy-3,5-dimethoxybenzoic acid) with d -galactose. The procedure using peracetylated glycosyl halides and sodium phenolates in aqueous acetone afforded the acetylated β-glycosides, which were deacetylated.

Characterization of two galactosidases extracted from wheat germ with a hydroalcoholic solvent

Alpha- and beta-D-galactosidases were characterized from a hydroalcoholic extract of wheat germ (Triticum vulgare). Kinetic constants (Vmax and KM) and the optimal pHs for the hydrolysis of p-nitrophenyl galactopyranosides by both enzymes were determined. These enzymes presented a high stability in hydroalcoholic medium and were inhibited by iodoacetamide and sodium p-hydroxy-mercuribenzoate.