Eucalyptus grandis resistance genes: an in silico search for potential targets in response to Myrtle Rust

Plants have evolved multiple layers of defence responses to pathogens. A first line of defence is the recognition and response to common pathogen-associated molecular patterns. Plants also exhibit pathogen-specific responses, which are mediated by expression of resistance genes (R-genes). R-gene products effectively block disease progression. A significant plant pathogen, which causes Myrtle Rust, has spread rapidly along the east coast of Australia since its first identification on the NSW Central Coast in 2010. This incursion is of concern due to the dominance of the Myrtaceae family in Australian vegetation. The recently published genome of Eucalyptus grandis has provided a valuable resource for the identification of potential resistance genes in this important Australian genus. In this study a search was conducted against the E. grandis genome for one important class of R-genes that incorporate nucleotide binding sites and leucine-rich repeat protein domains (NB-LRR). Predicted NB-LRR coding sequences were identified and analysis of the coding sequences revealed 11 gene models within the E. grandis genome. Scrutiny of these gene models, through E. grandis peptide homologues, identified a further 412 genes which contained both NB and LRR domains. The identification of these R-genes may provide researchers with a targeted approach to defence response studies to Myrtle Rust and other pathogens in E. grandis.