SAVE, INRAE, Bordeaux Sciences Agro, Université de Bordeaux, F-33140 Villenave d'Ornon, France.
LIPM, INRAE, Université de Toulouse, CNRS, Castanet-Tolosan, France.
Curr Biol. 2020 Oct 19;30(20):3897-3907.e4. doi: 10.1016/j.cub.2020.07.057. Epub 2020 Aug 13.
Mating types are self-incompatibility systems that promote outcrossing in plants, fungi, and oomycetes. Mating-type genes have been widely studied in plants and fungi but have yet to be identified in oomycetes, eukaryotic organisms closely related to brown algae that cause many destructive animal and plant diseases. We identified the mating-type locus of Plasmopara viticola, the oomycete responsible for grapevine downy mildew, one of the most damaging grapevine diseases worldwide. Using a genome-wide association approach, we identified a 570-kb repeat-rich non-recombining region controlling mating types, with two highly divergent alleles. We showed that one mating type was homozygous, whereas the other was heterozygous at this locus. The mating-type locus encompassed 40 genes, including one encoding a putative hormone receptor. Functional studies will, however, be required to validate the function of these genes and find the actual determinants of mating type. Our findings have fundamental implications for our understanding of the evolution of mating types, as they reveal a unique determinism involving an asymmetry of heterozygosity, as in sex chromosomes and unlike other mating-type systems. This identification of the mating-type locus in such an economically important crop pathogen also has applied implications, as outcrossing facilitates rapid evolution and resistance to harsh environmental conditions.
交配型是一种促进植物、真菌和卵菌中外交的自交不亲和系统。交配型基因在植物和真菌中得到了广泛的研究，但在与褐藻关系密切的卵菌中尚未被发现，而这些卵菌是引起许多破坏性动植物疾病的元凶。我们鉴定了引起葡萄霜霉病的卵菌——葡萄生单轴霉的交配型基因座，葡萄霜霉病是世界范围内对葡萄危害最大的疾病之一。我们使用全基因组关联方法，鉴定了一个控制交配型的 570kb 重复丰富的非重组区域，该区域包含两个高度分化的等位基因。我们表明，该基因座中的一个交配型是纯合的，而另一个是杂合的。交配型基因座包含 40 个基因，其中一个编码一个假定的激素受体。然而，需要进行功能研究来验证这些基因的功能，并找到交配型的实际决定因素。我们的发现对于理解交配型的进化具有重要意义，因为它们揭示了一种独特的决定论，涉及到与性染色体类似的杂合性不对称性，而不同于其他交配型系统。在这种经济上重要的作物病原体中鉴定交配型基因座也具有应用意义，因为杂交有利于快速进化和适应恶劣的环境条件。
