ological process is not significantly enriched 12 hpt with PS3. Moreover, the genes Nucleoredoxin-1, transcription factor WRKY40, b-1,3 glucanase, Enhanced Disease Susceptibility 1, Thaumatin-like protein 3, PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19645759 and Pathogenesis-related 1 were found to be specifically induced by SA whereas Jasmonate ZIM-domain protein, Fatty acid hydroperoxide lyase, and Allene oxide cyclase could be considered as JA-marker genes in grapevine. At 12 hpt, PS3 is unable to significantly upregulate all these above-mentioned specific SA- or JA-marker genes. However, a few genes were co-regulated by SA or JA and PS3. Indeed, 5% were common between PS3 and JA and 19% between PS3 and SA. For instance, the putative SA-Methyl Transferase 1, Carboxylesterase HSR203J like, Receptor-like kinase, two Glutathione S-transferase,, Avr9 elicitor response protein and Metalnicotianamine/oligopeptide transporter were co-induced by SA and PS3 suggesting that the SA-dependent pathway might be partly involved in the PS3 mode of action. To better understand the role of the SA- and JA-dependent pathways, SA and JA metabolites were quantified after PS3 and Lam treatment on uninfected grapevine plants. LC-ESI-MS/MS analysis revealed that PS3 was not able to elicit any significant SA and JA accumulation at 12 hpt and until 48 hpt. However, compared to PS3, Lam seems to elicit a transient increase in JA at 24 and 36 hpt. Beta-Glucan IR in Grapevine against Downy Mildew PS3 Primes the SA-dependent Defense Pathway during P. viticola Infection To characterize the putative involvement of phytohormones during PS3-IR, plants were treated with PS3 and 2 days later inoculated with downy mildew. SA and JA contents were quantified by LC-ESI-MS/MS from 0 to 8 dpi. Upon P. viticola inoculation, SA concentration detected in control plants was stable until 3 dpi, then raised quickly to reach 13800 ng g21 at 8 dpi, when sporulation appeared. Compared to the control plants, a higher SA content, which peaked to 5200 ng g21 at 0.5 dpi, was maintained until 3 dpi in PNU-100480 custom synthesis PS3-treated and infected plants. Then, SA concentration continued to rise slightly but less intensely than in control plants until 8 dpi. At this time point, pathogen spreading and sporulation were undetectable. In parallel, a non-significant variation in JA content 6 Beta-Glucan IR in Grapevine against Downy Mildew was detected in inoculated PS3-treated compared to adjuvanttreated plants. To gain further insight into the involvement of SA signaling during PS3-IR, expression of 2 SA-marker genes identified in this study was followed by qPCR. As PR-1 was not highly induced by SA, expression of genes encoding the b-1,3 glucanase and Nucleoredoxin 1 was followed after 0, 1 and 2 dpi in inoculated PS3- and adjuvant-treated plants. known SA synthetic analogue benzothiadiazole. Our results indicated that BTH was able to trigger grapevine resistance against downy mildew in a dose dependent manner, even if PS3 was always a more efficient resistance inducer. The Primed ROS-dependent Defense Pathway is Involved in Grapevine Triggered Immunity against P. viticola Infection PS3-IR is correlated with the priming of defense responses after P. viticola inoculation, including the SA-dependent pathway and with a specific H2O2 production, callose deposition and HR-like cell death . Therefore, gene expression of a well-established ROS-related gene, Respiratory burst oxidative homolog D and a HR marker gene, HSR203J were analyzed by qPCR in PS3-treated plants du