Bian Zhuyun, Xu Ziyan, Peer Anushka, Choi Yeseul, Priest Shelby J, Akritidou Konstantina, Dasgupta Ananya, Dahlmann Tim A, Kück Ulrich, Nowrousian Minou, Sachs Matthew S, Sun Sheng, Heitman Joseph
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA.
Department of Biology, Texas A&M University, College Station, Texas, USA.
mBio. 2025 Apr 9;16(4):e0022325. doi: 10.1128/mbio.00223-25. Epub 2025 Feb 25.
Fungal sexual reproduction is controlled by the mating-type () locus. In contrast to a majority of species in the phylum Basidiomycota that have tetrapolar mating-type systems, the opportunistic human pathogen employs a bipolar mating-type system, with two mating types ( and α) determined by a single locus that is unusually large (~120 kb) and contains more than 20 genes. While several genes are associated with mating and sexual development, others control conserved cellular processes (e.g., cargo transport and protein synthesis), of which five (, , , , and ) have been hypothesized to be essential. In this study, through genetic analysis involving sporulation of heterozygous diploid deletion mutants, as well as in some cases construction and analyses of conditional expression alleles of these genes, we confirmed that with the exception of , both alleles of the other four genes are indeed essential for cell viability. We further showed that while is not essential, its function is critical for infectious spore production, faithful cytokinesis, adaptation for growth at high temperature, and pathogenicity . Our results demonstrate the presence of essential genes in the locus that are divergent between cells of opposite mating types. We discuss possible mechanisms to maintain functional alleles of these essential genes in a rapidly evolving genomic region in the context of fungal sexual reproduction and mating-type evolution.IMPORTANCESexual reproduction is essential for long-term evolutionary success. Fungal cell-type identity is governed by the locus, which is typically rapidly evolving and highly divergent between different mating types. In this study, we show that the and α alleles of four genes encoded in the locus of the opportunistic human fungal pathogen are essential. We demonstrate that a fifth gene, , which had been predicted to be essential, is in fact dispensable for cell viability. However, a functional allele is important for cytokinesis and fungal pathogenicity. Our study highlights the need for careful genetic analyses in determining essential genes, which is complementary to high-throughput approaches. Additionally, the presence of essential genes in the locus of provides insights into the function, maintenance, and evolution of these fast-evolving genomic regions.
真菌有性生殖受交配型（MAT）位点控制。与担子菌门中大多数具有四极性交配型系统的物种不同，机会性人类病原体新生隐球菌采用双极性交配型系统，其两种交配型（a和α）由一个异常大（约120 kb）且包含20多个基因的单一MAT位点决定。虽然几个MAT基因与交配和有性发育相关，但其他基因控制保守的细胞过程（如货物运输和蛋白质合成），其中五个基因（STE12、HMG2、SXI1α、SXI2α和PRF1）被推测是必需的。在本研究中，通过涉及杂合二倍体缺失突变体孢子形成的遗传分析，以及在某些情况下构建和分析这些基因的条件表达等位基因，我们证实除了STE12外，其他四个MAT基因的两个等位基因确实对细胞活力至关重要。我们进一步表明，虽然STE12不是必需的，但其功能对于感染性孢子产生、准确的胞质分裂、适应高温生长和致病性至关重要。我们的结果表明，MAT位点中存在必需基因，这些基因在相反交配型的细胞之间存在差异。我们讨论了在真菌有性生殖和交配型进化的背景下，在快速进化的基因组区域中维持这些必需基因功能等位基因的可能机制。
重要性
有性生殖对于长期进化成功至关重要。真菌细胞类型身份由MAT位点控制，该位点通常快速进化且在不同交配型之间高度分化。在本研究中，我们表明机会性人类真菌病原体新生隐球菌MAT位点编码的四个基因的a和α等位基因是必需的。我们证明，一个曾被预测为必需的第五个基因STE12，实际上对于细胞活力是可有可无的。然而，功能性的STE12等位基因对于胞质分裂和真菌致病性很重要。我们的研究强调了在确定必需基因时进行仔细遗传分析的必要性，这与高通量方法互补。此外，新生隐球菌MAT位点中必需基因的存在为这些快速进化的基因组区域的功能、维持和进化提供了见解。
