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

ABSTRACT: 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 fungus Magnaporthe 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 fungus M. 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 synthase Ace1 and two variants of the effector gene AVR-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 segmental duplication of core-chromosomes and might contribute to adaptive evolution of the blast fungus.

SUBMITTER: Langner T

PROVIDER: S-EPMC7909708 | biostudies-literature | 2021 Feb

REPOSITORIES: biostudies-literature

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

Langner Thorsten T Harant Adeline A Gomez-Luciano Luis B LB Shrestha Ram K RK Malmgren Angus A Latorre Sergio M SM Burbano Hernán A HA Win Joe J Kamoun Sophien S

PLoS genetics 20210216 2

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 fungus Magnaporthe 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 invest ...[more]

PMID: 33591993

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Project description:Transcriptional changes were monitored in the wheat cultivar Renan 24 hours post i noculation with adapted and non-adapted Magnaporthe isolates using the Affymetrix wheat genome array GeneChip®. Wheat plants cv. Renan were grown in a peat and sand (1:1) mix at 23 C in a Sanyo Fitotron growth cabinet (Sanyo Gallenkamp PLC, Loughborough, U.K.) with a 16/8 h, light/dark cycle. Three Magnaporthe isolates were used in this expt, two wheat-adapted isolates (BR32, BR37) and one wheat non-adapted isolate (BR29). Magnaporthe isolates were grown for eleven days on Complete Media Agar at 25 C under a 16/8h, light/dark cycle. Conidia were harvested by flooding the plates with 5 mL of sterile inoculation solution [0.25% (w/v) gelatine and 0.01% (v/v) Tween 20] and scraping the conidia from the surface using a sterile glass rod. Conidia were filtered through sterile miracloth and the density adjusted to 1 x 10 5 conidia mL-1 with inoculation solution. Fourteen day old wheat seedlings mist inoculated with 4 mL of a Magnaporthe conidia suspension and plants were sealed in plastic propagators to maintain relative humidity c.100% and kept at 25 C in the dark for the first 24 hours post inoculation (hpi). Inoculation solution without Magnaporthe conidia was used as a mock-inoculation control. Leaf samples were collected 24 hpi for transcriptomics analysis from three independent biological experiments. Leaf tissue was ground under liquid nitrogen and total RNA extracted using a QIAquick RNeasy Plant Extraction Kit (Qiagen, Hilden, Germany), followed by TURBO DNaseTM (Ambion, Texas, U.S.A.) treatment. RNeasy Mini Spin column purification (Qiagen) was used to further purify RNA samples for array hybridisation. RNA quality checks, cRNA conversion and Affymetrix genome array hybridisation was carried out by the Nottingham Arabidopsis Stock Centre (NASC) array hybridisation service (http://affymetrix.arabidopsis.info/). ****[PLEXdb(http://www.plexdb.org) has submitted this series at GEO on behalf of the original contributor, Graham McGrann. The equivalent experiment is TA24 at PLEXdb.]

Dataset Information

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

Publications

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

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