April 21, 2020  |  

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

Authors: Peng, Zhao and Oliveira-Garcia, Ely and Lin, Guifang and Hu, Ying and Dalby, Melinda and Migeon, Pierre and Tang, Haibao and Farman, Mark and Cook, David and White, Frank F and Valent, Barbara and Liu, Sanzhen

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.

Journal: PLoS genetics
DOI: 10.1371/journal.pgen.1008272
Year: 2019

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