Effector gene reshuffling involves dispensable mini-chromosomes in the wheat blast fungus.

• Main Authors: Zhao Peng, Ely Oliveira-Garcia, Guifang Lin, Ying Hu, Melinda Dalby, Pierre Migeon, Haibao Tang, Mark Farman, David Cook, Frank F White, Barbara Valent, Sanzhen Liu
• Format: Article
• Language: English
• Published: Public Library of Science (PLoS) 2019-09-01
• Series: PLoS Genetics
• Online Access: https://doi.org/10.1371/journal.pgen.1008272
• ISSN: 1553-7390; 1553-7404

Newly emerged wheat blast disease is a serious threat to global wheat production. Wheat blast is caused by a distinct, exceptionally diverse lineage of the fungus causing rice blast disease. Through sequencing a recent field isolate, we report a reference genome that includes seven core chromosomes and mini-chromosome sequences that harbor effector genes normally found on ends of core chromosomes in other strains. No mini-chromosomes were observed in an early field strain, and at least two from another isolate each contain different effector genes and core chromosome end sequences. The mini-chromosome is enriched in transposons occurring most frequently at core chromosome ends. Additionally, transposons in mini-chromosomes lack the characteristic signature for inactivation by repeat-induced point (RIP) mutation genome defenses. Our results, collectively, indicate that dispensable mini-chromosomes and core chromosomes undergo divergent evolutionary trajectories, and mini-chromosomes and core chromosome ends are coupled as a mobile, fast-evolving effector compartment in the wheat pathogen genome.