Abstract
Macadamia is an evergreen tree belonging to the Proteaceae family. The two commercial macadamia species, Macadamia integrifolia and M. tetraphylla, are highly prized for their edible kernels. The M. integrifolia genome was recently sequenced, but the genome of M. tetraphylla has to date not been published, which limits the study of biological research and breeding in this species. This study reports a high-quality genome sequence of M. tetraphylla based on the Oxford Nanopore Technologies technology and high-throughput chromosome conformation capture techniques (Hi-C). An assembly of 750.87 Mb with 51.11 Mb N50 length was generated, close to the 740 and 758 Mb size estimates by flow cytometry and k-mer analysis, respectively. Genome annotation indicated that 61.42% of the genome is composed of repetitive sequences and 34.95% is composed of long terminal repeat retrotransposons. Up to 31,571 protein-coding genes were predicted, of which 92.59% were functionally annotated. The average gene length was 6,055 bp. Comparative genome analysis revealed that the gene families associated with defense response, lipid transport, steroid biosynthesis, triglyceride lipase activity, and fatty acid metabolism are expanded in the M. tetraphylla genome. The distribution of fourfold synonymous third-codon transversion showed a recent whole-genome duplication event in M. tetraphylla. Genomic and transcriptomic analysis identified 187 genes encoding 33 crucial oil biosynthesis enzymes, depicting a comprehensive map of macadamia lipid biosynthesis. Besides, the 55 identified WRKY genes exhibited preferential expression in root as compared to that in other tissues. The genome sequence of M. tetraphylla provides novel insights for breeding novel varieties and genetic improvement of agronomic traits.
Highlights
Macadamia is an evergreen nut tree belonging to the Proteaceae family, genus Macadamia F
The M. tetraphylla was sequenced on the Oxford Nanopore Technologies (ONT) platform
The M. tetraphylla genome was assembled into 4,335 contigs, with an N50 of 1,182,547 bp (Table 1)
Summary
Macadamia is an evergreen nut tree belonging to the Proteaceae family, genus Macadamia F. Due to the large-scale commercial cultivation in Hawaii (United States) in 1948 (Ahmad Termizi et al, 2014), macadamia was named as Hawaiian Nuts, which is native to the subtropical rainforest of Queensland, New South Wales, Australia (Neal et al, 2010; Shapcott and Powell, 2011). The commercial growing areas of macadamia are located in the tropical and subtropical belts, the traditional cultivated area is in the United States and Australia (Trueman and Turnbull, 1994). The total macadamia planted area has rapidly grown over the past decade because the cultivation technology is simple, planting high income, the plants are more cold-resistant than rubber trees, bananas, and other traditional tropical crops, yet very suitable for the cool weather of tropical and subtropical countries. The largest macadamia orchard area is in China (300,000 ha), followed by South Africa, Australia, Kenya, Guatemala, and the United States in that order
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
