Low level of polymorphism in two putative <it>NPR1 </it>homologs in the <it>Vitaceae </it>family

<p>Abstract</p> <p>Background</p> <p>Grapevine is subjected to numerous pests and diseases resulting in the use of phytochemicals in large quantities. The will to decrease the use of phytochemicals leads to attempts to find alternative strategies, implying knowledge of defence mechanisms. Numerous studies have led to the identification of signalling pathways and regulatory elements involved in defence in various plant species. Nonexpressor of Pathogenesis Related 1 (NPR1) is an important regulatory component of systemic acquired resistance (SAR) in <it>Arabidopsis thaliana</it>.</p> <p>Results</p> <p>Two putative homologs of <it>NPR1 </it>gene were found in the two sequenced grapevine genomes available in the Genoscope database for line 40024 and in the IASMA database for Pinot noir ENTAV 115. We named these two <it>NPR1 </it>genes of <it>Vitis vinifera </it>: <it>VvNPR1.1 </it>and <it>VvNPR1.2</it>. A PCR-based strategy with primers designed on exons was used to successfully amplify <it>NPR1 </it>gene fragments from different <it>Vitaceae </it>accessions. Sequence analyses show that <it>NPR1.1 </it>and <it>NPR1.2 </it>are highly conserved among the different accessions not only <it>V. vinifera </it>cultivars but also other species. We report nucleotide polymorphisms in <it>NPR1.1 </it>and <it>NPR1.2 </it>from fifteen accessions belonging to the <it>Vitaceae </it>family. The ratio of nonsynonymous to synonymous nucleotide substitutions determines the evolutionary pressures acting on the <it>Vitaceae NPR1 </it>genes. These genes appear to be experiencing purifying selection. In some of the species we have analysed one of the two alleles of <it>NPR1.1 </it>contains a premature stop codon. The deduced amino acid sequences share structural features with known NPR1-like proteins: ankyrin repeats, BTB/POZ domains, nuclear localization signature and cysteines. Phylogenetic analyses of deduced amino acid sequences show that VvNPR1.1 belongs to a first group of NPR1 proteins known as positive regulators of SAR and VvNPR1.2 belongs to a second group of NPR1 proteins whose principal members are AtNPR3 and AtNPR4 defined as negative regulators of SAR.</p> <p>Conclusion</p> <p>Our study shows that <it>NPR1.1 </it>and <it>NPR1.2 </it>are highly conserved among different accessions in the <it>Vitaceae </it>family. VvNPR1.1 and VvNPR1.2 are phylogenetically closer to the group of positive or negative SAR regulators respectively.</p> <p>Reviewers</p> <p>This article was reviewed by Fyodor Kondrashov, Purificación López-García and George V. Shpakovski.</p>