Austropuccinia psidii, causing myrtle rust, has a gigabase-sized genome shaped by transposable elements

Area of Science:

• Plant pathology
• Genomics
• Evolutionary biology

Background:

• Austropuccinia psidii is a globally invasive fungal pathogen causing rust disease in Myrtaceae.
• The pandemic biotype has spread widely, impacting over 480 species and causing extinctions.
• Understanding its genome is critical for managing its spread and effects.

Purpose of the Study:

• To assemble a highly contiguous genome of the pandemic biotype of Austropuccinia psidii.
• To investigate the role of transposable elements in the genome evolution of this invasive pathogen.
• To provide a resource for molecular and evolutionary studies of A. psidii pathogenicity.

Main Methods:

• Genome assembly of the pandemic biotype of Austropuccinia psidii.
• Analysis of transposable element content and distribution.
• Comparative genomic analysis with other Pucciniales.

Main Results:

• Assembly of the largest fungal genome to date (over 1 Gb haploid size).
• Massive genome expansion driven by transposable element (TE) bursts, with over 90% of the genome covered by TEs.
• Low GC content (33.8%) and depleted CpG sites due to deamination events, with increased intergenic distances.

Conclusions:

• Transposable elements have profoundly shaped the genome evolution of Austropuccinia psidii.
• The assembled genome provides a vital resource for understanding pathogenicity and developing control strategies.
• Insights into genome structure can inform efforts to combat the spread of this devastating plant disease.