The nucleotide sequence of the genomic RNA2 (3774 nucleotides) of grapevine fanleaf virus strain F13 was determined from overlapping cDNA clones and its genetic organization was deduced. Two rapid and efficient methods were used for cDNA cloning of the 5' region of RNA2. The complete sequence contained only one long open reading frame of 3555 nucleotides (1184 codons, 131K product). The analysis of the Nterminal sequence of purified coat protein (CP) and identification of its C-terminal residue have allowed the CP cistron to be precisely positioned within the polyprotein. The CP produced by proteolytic cleavage at the Arg/Gly site between residues 680 and 681 contains 504 amino acids (Mr 56019) and has hydrophobic properties. The Arg/Gly cleavage site deduced by N-terminal amino acid sequence analysis is the first for a nepovirus coat protein and for plant viruses expressing their genomic RNAs by polyprotein synthesis. Comparison of GFLV RNA2 with M RNA of cowpea mosaic comovirus and with RNA2 of two closely related nepoviruses, tomato black ring virus and Hungarian grapevine chrome mosaic virus, showed strong similarities among the 3' non-coding regions but less similarity among the 5' end non-coding sequences than reported among other nepovirus RNAs.

Background: In traditional vine areas, the production should present a typicity that partly depends on the grapevine variety. Therefore, vine improvement is considered difficult because of the limited choice in the natural variability of the cultivars within the limits of their characteristics. A possibility to circumvent this problem is the use of somatic variability. In vitro somatic embryogenesis and organogenesis can lead to genotypic and phenotypic variations, described as somaclonal variation, that could be useful for the selection of improved grapevine genotypes.

Background: Grapevine protection against diseases needs alternative strategies to the use of phytochemicals, implying a thorough knowledge of innate defense mechanisms. However, signalling pathways and regulatory elements leading to induction of defense responses have yet to be characterized in this species. In order to study defense response signalling to pathogens in Vitis vinifera, we took advantage of its recently completed genome sequence to characterize two putative orthologs of NPR1, a key player in salicylic acid (SA)-mediated resistance to biotrophic pathogens in Arabidopsis thaliana.

SUMMARYThe F 13 isolate of grapevine fanleaf virus (GFLV) differs from other isolates in that it induces severe symptoms on Chenopodium quinoa. We show here that its particles contain three RNA species with sizes, estimated by electrophoresis in agarose gels containing formaldehyde, of 6800 nucleotides (RNA 1), 3900 nucleotides (RNA2) and 1150 nucleotides (RNA3). The three RNA species are polyadenylated and probably have a genome-linked protein at their 5' end. RNA1 and RNA2 are known to be genomic RNAs. Evidence for the satellite nature of RNA3 came from Northern blot analysis with DNA probes. A probe originating from the 3' end region of RNA3 and corresponding to one-third of the molecule did not hybridize with either RNA1 or RNA2. Conversely 3'-terminal cDNA probes of RNA1 and RNA2 did not hybridize significantly to RNA3. Further proof of the satellite nature of RNA3 is that it depends on RNA1 and RNA2 for its multiplication in C. quinoa. RNA3 acts as mRNA in wheatgerm extract and directs the synthesis of a Mr 39000 protein.

BackgroundGenes belonging to the pathogenesis related 10 (PR10) group have been studied in several plant species, where they form multigene families. Until now, such an analysis has not been performed in Vitis vinifera, although three different PR10 genes were found to be expressed under pathogen attack or abiotic stress, and during somatic embryogenesis induction. We used the complete genome sequence for characterising the whole V. vinifera PR10 gene family. The expression of candidate genes was studied in various non-treated tissues and following somatic embryogenesis induction by the auxin 2,4-D.ResultsIn addition to the three V. vinifera PR10 genes already described, namely VvPR10.1, VvPR10.2 and VvPR10.3, fourteen different PR10 related sequences were identified. Showing high similarity, they form a single cluster on the chromosome 5 comprising three pseudogenes. The expression of nine different genes was detected in various tissues. Although differentially expressed in non-treated plant organs, several genes were up-regulated in tissues treated with 2,4-D, as expected for PR genes.ConclusionsPR10 genes form a multigene family in V. vinifera, as found in birch, apple or peach. Seventeen closely related PR10 sequences are arranged in a tandem array on the chromosome 5, probably reflecting small-scale duplications during evolution. Various expression patterns were found for nine studied genes, highlighting functional diversification. A phylogenetic comparison of deduced proteins with PR10 proteins of other plants showed a characteristic low intraspecific variability. Particularly, a group of seven close tandem duplicates including VvPR10.1, VvPR10.2 and VvPR10.3 showed a very high similarity, suggesting concerted evolution or/and recent duplications.