Department ECOBIO, UMR CNRS 6553, Université Rennes 1, Rennes, France.
Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, Canada.
Proc Biol Sci. 2022 Aug 10;289(1980):20220971. doi: 10.1098/rspb.2022.0971.
Heterokaryosis is a system in which genetically distinct nuclei coexist within the same cytoplasm. While heterokaryosis dominates the life cycle of many fungal species, the transcriptomic changes associated with the transition from homokaryosis to heterokaryosis is not well understood. Here, we analyse gene expression profiles of homokaryons and heterokaryons from three phylogenetically and reproductively isolated lineages of the filamentous ascomycete . We show that heterokaryons are transcriptionally distinct from homokaryons in the sexual stage of development, but not in the vegetative stage, suggesting that the phenotypic switch to fertility in heterokaryons is associated with major changes in gene expression. Heterokaryon expression is predominantly defined by additive effects of its two nuclear components. Furthermore, allele-specific expression analysis of heterokaryons with varying nuclear ratios show patterns of expression ratios strongly dependent on nuclear ratios in the vegetative stage. By contrast, in the sexual stage, strong deviations of expression ratios indicate a co-regulation of nuclear gene expression in all three lineages. Taken together, our results show two levels of expression control: additive effects suggest a nuclear level of expression, whereas co-regulation of gene expression indicate a heterokaryon level of control.
异核体是一种在同一细胞质中存在遗传上不同核的系统。虽然异核体主导着许多真菌物种的生命周期，但从同核体到异核体的转变所伴随的转录组变化还不是很清楚。在这里，我们分析了丝状子囊菌三个系统发育和繁殖隔离谱系的同核体和异核体的基因表达谱。我们表明，异核体在有性发育阶段与同核体在转录上是不同的，但在营养阶段则没有，这表明异核体向可育性的表型转变与基因表达的重大变化有关。异核体的表达主要由其两个核成分的加性效应决定。此外，对具有不同核比的异核体的等位基因特异性表达分析表明，在营养阶段，表达比与核比强烈相关。相比之下，在有性阶段，表达比的强烈偏差表明在所有三个谱系中核基因表达的共同调控。总的来说，我们的结果显示了两种表达控制水平：加性效应表明核水平的表达，而基因表达的共同调控则表明异核体水平的控制。
