Genomic rearrangements generate hypervariable mini-chromosomes in host-specific isolates of the blast fungus

by Thorsten Langner, Adeline Harant, Luis B. Gomez-Luciano, Ram K. Shrestha, Angus Malmgren, Sergio M. Latorre, Hern án A. Burbano, Joe Win, Sophien Kamoun

Supernumerary mini-chromosomes–a unique type of genomic structural variation–have been implicated in the emergence of virulence traits in plant pathogenic fungi. However, the mechanisms that facilitate the emergence and maintenance of mini-chromosomes across fungi remain poorly understood. In the blast fungusMagnaporthe oryzae (Syn.Pyricularia oryzae), mini-chromosomes have been first described in the early 1990s but, until very recently, have been overlooked in genomic studies. Here we investigated structural variation in four isolates of the blast fungusM.oryzae from different grass hosts and analyzed the sequences of mini-chromosomes in the rice, foxtail millet and goosegrass isolates. The mini-chromosomes of these isolates turned out to be highly diverse with distinct sequence composition. They are enriched in repetitive elements and have lower gene density than core-chromosomes. We identified several virulence-related genes in the mini-chromosome of the rice isolate, including the virulence-related polyketide synthaseAce1 and two variants of the effector geneAVR-Pik. Macrosynteny analyses around these loci revealed structural rearrangements, including inter-chromosomal translocations between core- and mini-chromosomes. Our findings provide evidence that mini-chromosomes emerge from structural rearrangements and ...

Source: PLoS Genetics - February 16, 2021 Category: Genetics & Stem Cells Authors: Thorsten Langner Source Type: research