Disease Resistance Gene Analysis on Chromosome 11 Across Ten Oryza Species

R (Resistance) genes are a major defense mechanism for protecting plants from diseases and recognize pathogen effectors to trigger genetic mechanisms. Approximately 20% of R genes in cultivated rice are located on chromosome 11. Here we analyzed the abundance and distribution of R-gene analogues on chromosome 11 across 10 different Oryza species with three different genome type (AA, BB & FF) and the outgroup (Leersia perrieri). The most common class of R-genes contain Nucleotide Binding Site (NBS) and Leucine Rich Repeat (LRR) domains, together with other additional domains such as Coiled Coil, Pkinase, Transmembrane, Toll-IL-IR, and the WRKY domain. The HMM-profile of each domain, downloaded from Pfam, was used as query to search the annotated proteomes of Oryza. Twelve combinations of these domains were identified in all species, with NBS-LRR and LRR-Pkinase combination present in more than 75% of R genes. No significant variation was found in the number of NBS-LRR and LRR-Pkinase containing R-genes among all the Oryza species. However, we detected a significant reduction in R genes in BB and FF genomes as compared to the AA genome and L. perrieri.  Based on a 70% similarity index, 75% of the NBS-LRR genes could be clustered, and the remaining 25% were found to be singletons indicating that NBS-LRR genes are one of the most rapidly evolving gene families in the genome. Further analysis of R-genes genus-wide will help us to identify and understand 15 MYA of evolutionary history of the majority of disease resistance gene in the Oryza genus