No abstract

A synthetic gene encoding a single chain Fv fragment of an antibody directed against the nuclear inclusion a (NIa) protein of potato virus Y (PVY) was used to transform two commercial potato cultivars (Claustar and BF15). The NIa protease forms the nuclear inclusion body A and acts as the major protease in the cleavage of the viral polyprotein into functional proteins. Immunoblot analysis showed that most of the resulting transgenic plants accumulate high levels of the transgenic protein. Furthermore, a majority of the selected transgenic lines showed an efficient and complete protection against the challenge virus after mechanical inoculation with PVYO strain. Two transgenic lines showed an incomplete resistance with delayed appearance of symptoms accompanied by low virus titers, whereas one line developed symptoms during the first days after inoculation but recovered rapidly, leading to a low virus accumulation rate. These results confirm that expression of scFv antibody is able to inhibit a crucial step in the virus multiplication, such as polyprotein cleavage is a powerful strategy for engineered virus resistance. It can lead to a complete resistance that was not obtained previously by expression of scFv directed against the viral coat protein.

Forty three strains were isolated from knots induced by Pseudomonas savastanoi in different olive cultivars. All the selected bacteria were shown to produce variable amounts of the plant growth hormone indole-3-acetic acid (IAA). Amplification of the intergenic transcribed spacers (ITS) between 16S and 23S rDNA genes, allowed the clustering of the isolates into seven distinct groups. All isolates from ITS group 1 were positive to the Pseudomonas savastanoi pv. savastanoi specific iaa L gene as shown by PCR. Partial sequencing of 16S rDNA gene confirmed the identity of these isolates to Pseudomonas savastanoi strains and allowed to tentatively assign the other isolates from the remaining ITS groups to Pantoea oleae/agglomerans, Burkholderia cepacia, Pseudomonas putida, Stenotrophomonas maltophilia and Hafnia alvei. Identification of endophytic knot-derived isolates revealed association of various saprophytic and putative human pathogenic bacteria with P. savastanoi pv. savastanoi in knot environment of olive infected trees.

The main objective of this investigation was to identify a collection of actinomycetes isolates and to study the influence of amendment [municipal solid waste compost (MSWC) and farmyard manure (FM)] on their distribution in agricultural soil. For this purpose, a phenotypic and molecular characterization of 226 isolates collected from soil (with and without amendment) and 55 isolates from MSWC and FM was developed. The phenotypic study showed that the majority of strains isolated belong to the genus Streptomyces. By using the 16S rDNA polymerase chain reaction-restriction fragment length polymorphism method (restriction digest using six enzymes AluI, HhaI, MspI, TaqI, RsaI and HaeIII), two clusters were found: Streptomyces, dominant genus and Amycolatopsis, followed by Nocardioides. This result agreed with phylogeny revealed by 16S rDNA sequencing. The number of these actinomycetes in soil increased with FM or MSWC application. The studied soil is a potential source for isolation of actinomycetes, especially Streptomyces, and the application of organic amendment to the soil appeared to have an impact on the diversity of actinomycetes. Amendment of the soil with MSWC and FM significantly increased the number of actinomycetes due to the contribution of bacteria originally contained in biowastes and/or by stimulation of the endogenous soil micro-organisms.

RésuméL'extraction des acides nucléiques à partir du compost permet de détecter des microorganismes non détectables par les méthodes classiques. En effet, nous avons essayé trois méthodes différentes et nous avons remarqué l'importance d'une bonne lyse cellulaire pour la libération de l'ADN (8 cycles de congélation-décongélation). L'utilisation du mélange CTAB-PVPP a été remarquable puisque ce dernier a permis d'éliminer des impuretés, ce qui s'est traduit par un éclaircissement des échantillons bruns originels. La méthode de purification la plus efficace est celle qui utilise le mélange PEG-NaCl Abstract