Biomedical subjects

Olivier Lemaire

Publications and source records attributed to Olivier Lemaire.

3 recordsLinked to original sources

PubMed2007

A sensitive one-step real-time RT-PCR method for detecting Grapevine leafroll-associated virus 2 variants in grapevine.

Grapevine leafroll syndrome is caused by a complex of up to nine different Grapevine leafroll-associated viruses (GLRaV-1-9) with GLRaV-2 being reported as one of the most variable species of this group. Many methods, including indexing, serological and molecular procedures, have been developed for the detection of GLRaV-2. However, due to the low concentration of the virus in plants and the high variability of GLRaV-2, a method with improved sensitivity and with the capacity to detect of all known variants is required. Such improvement is essential for grapevine rootstocks, as these are suspected to harbour frequent GLRaV-2 infections difficult to detect, thus contributing to the spread of the leafroll disease. The development of new universal primers is described using a target sequence located in the 3' end of the virus genome. These primers were combined with a one-step SYBR Green real-time RT-PCR assay to achieve quantitative detection. All 43 GLRaV-2 isolates tested in this study were identified readily and reproducibly, regardless of their geographical origin or variety of grapevine. Using the procedure developed in this study, the sensitivity was increased 125 times compared to a conventional single-tube RT-PCR. This real-time method opens new perspectives for the sanitary selection of grapevine and in leafroll 2 disease monitoring.

3' Flanking Region↗

PubMed2005

Functional characterization of the Beet necrotic yellow vein virus RNA-5-encoded p26 protein: evidence for structural pathogenicity determinants.

A Beet necrotic yellow vein virus isolate containing a fifth RNA is present in the Pithiviers area of France. A full-length cDNA clone of RNA-5 was obtained and placed under the control of a T(7)-RNA-pol promoter that allowed the production of infectious transcripts. "Pithiviers" isolate-specific necrotic symptoms were obtained on Chenopodium quinoa when RNA-5-encoded p26 was expressed either from RNA-5 or from an RNA-3-derived replicon. By using haemagglutinin- and green fluorescent protein-tagged constructs, virally expressed p26-fusion proteins induced the same necrotic local lesions on host plants and were localized mainly in the nucleus of infected cells. Deletion mutagenesis permitted identification of two domains, responsible respectively for nuclear export and cytoplasmic retention of the p26 mutated proteins. By using a yeast two-hybrid system, Gal4DB-p26 protein self-activated transcription of the His3 reporter gene. The p26 transcription-activation domain was located within its first 55 aa and has been studied by alanine scanning. Resulting p26 mutants were tested for their capability to induce necrotic symptoms and to localize in the nuclear compartment.

Amino Acid Sequence↗

PubMed2005

Phylogenetic analysis of isolates of Beet necrotic yellow vein virus collected worldwide.

A study of molecular diversity was carried out on 136 sugar beets infected with Beet necrotic yellow vein virus (BNYVV, Benyvirus) collected worldwide. The nucleotide sequences of the RNA-2-encoded CP, RNA-3-encoded p25 and RNA-5-encoded p26 proteins were analysed. The resulting phylogenetic trees allowed BNYVV to be classified into groups that show correlations between the virus clusters and geographic origins. The selective constraints on these three sequences were measured by estimating the ratio between synonymous and non-synonymous substitution rates (omega) with maximum-likelihood models. The results suggest that selective constraints are exerted differently on the proteins. CP was the most conserved, with mean omega values ranging from 0.12 to 0.15, while p26 was less constrained, with mean omega values ranging from 0.20 to 0.33. Selection was detected in three amino acid positions of p26, with omega values of about 5.0. The p25 sequences presented the highest mean omega values (0.36-1.10), with strong positive selection (omega=4.7-54.7) acting on 14 amino acids, and particularly on amino acid 68, where the omega value was the highest so far encountered in plant viruses.

Beta vulgaris↗