A recent study published by Mateus et al.  claimed that 18 “mating-related” genes are differentially expressed in the model arbuscular mycorrhizal fungus (AMF) Rhizophagus irregularis when genetically distinct fungal strains co-colonize a host plant. To clarify the level of evidence for this interesting conclusion, we first aimed to validate the functional annotation of these 18 R. irregularis genes using orthology predictions. These analyses revealed that, although sequence relationship exists, only 2 of the claimed 18 R. irregularis mating genes are potential orthologues to validated fungal mating genes. We also investigated the RNA-seq data from Mateus et al.  using classical RNA-seq methods and statistics. This analysis found that the over-expression during strain co-existence was not significant at the typical cut-off of the R. irregularis strains DAOM197198 and B1 in plants. Overall, we do not find convincing evidence that the genes involved have functions in mating, or that they are reproducibly up or down regulated during co-existence in plants.
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We thank the editor, anonymous reviewers, as well as Vasilis Kokkoris, Jeanne Ropars, and Ricardo. Vega, Toni Gabaldon, Jason Slot, Stefano Ghignone, and the Bioinformatics facilities of the LRSV in Toulouse for their comments on an earlier version of this manuscript. We also thank Jeanne Ropars for providing key analyses for this study. N.C. research is funded by the discovery program of the Natural Sciences and Engineering Research Council (RGPIN-2020-05643) and the Discovery Accelerator Supplements Program (RGPAS-2020-00033). N.C. is a University of Ottawa Research Chair in Microbial Genomics.
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Malar C, M., Roux, C. & Corradi, N. Regulation of mating genes during arbuscular mycorrhizal isolate co-existence—where is the evidence?. ISME J (2021). https://doi.org/10.1038/s41396-021-00924-y