Harvesting the Macadamia Genome

The angiosperm plant family Proteaceae first appeared in the rainforests of the southern supercontinent Gondwana early in the history of flowering plants. The largest family in the distinct basal eudicot order Proteales, little is known of the composition and organisation of the Proteaceae genome. The nut tree macadamia is the only Proteacean food crop and the first of Australia’s flora to be cultivated and marketed worldwide. The Macadamia genome sequence project was initiated in 2011 within the native range of the subtropical rainforest species of Macadamia at Southern Cross University and University of Queensland.

We have generated and assembled shotgun genome sequence data for a widely grown Macadamia integrifolia cultivar, 741. Markers identified and developed from initial  sequence reads for cultivar identification, mapping, pedigree and gene-flow studies are providing support for the Australian Macadamia Breeding Program. The complete and annotated chloroplast genome sequence, to our knowledge the first in the Proteaceae, provides a reference for phylogenetic resolution among basal eudicots and within the Proteaceae.

The draft genome assembly is estimated to cover 80% of the Macadamia integrifolia genome. Bioinformatic estimates suggest that the genome size is approximately 780 megabases. The draft genome assembly is estimated to cover approximately 80% of the genome with a relatively low repetitive content of 30%.  Analysis and annotation of genome assemblies has lead to the identification of around 29,000 genes. This provides a unique opportunity to identify genes associated with specific traits of importance to the macadamia industry and will inform further studies across the Proteales.