ARCHIPELAGO: a dedicated resource for exploiting past, present, and future genomic data on disease resistance regulation in rice.

Large amounts of expression data dealing with biotic stresses in rice have been produced in the past 5 years. Here, we extensively review approximately 70 publications and gather together information on more than 2,500 genes of the rice defense arsenal. This information was integrated into the OryGenesDB database. Several genes (e.g., metallothioneins and PBZ1) appear to be hallmarks of rice-pathogen interactions. Cross-referencing this information with the rice kinome highlighted some defense genes and kinases as possible central nodes of regulation. Cross referencing defense gene expression and quantitative trait loci (QTL) information identified some candidate genes for QTL. Overall, pathogenesis-related genes and disease regulators were found to be statistically associated with disease QTL. At the genomic level, we observed that some regions are richer than others and that some chromosomes (e.g., 11 and 12), which contain a lot of resistance gene analogs, have a low content of defense genes. Finally, we show that classical defense genes and defense-related genes such as resistance genes are preferentially organized in clusters. These clusters are not always coregulated and individual paralogs can show specific expression patterns. Thus, the rice defense arsenal has an ARCHIPELAGO-like genome structure at the macro and micro level. This resource opens new possibilities for marker-assisted selection and QTL cloning.