Department of Biochemistry & Molecular Biology, Monash University, Clayton, Victoria, Australia.
PLoS One. 2012;7(9):e46243. doi: 10.1371/journal.pone.0046243. Epub 2012 Sep 28.
Understanding multicellular fungal structures is important for designing better strategies against human fungal pathogens. For example, the ability to form multicellular biofilms is a key virulence property of the yeast Candida albicans. C. albicans biofilms form on indwelling medical devices and are drug resistant, causing serious infections in hospital settings. Multicellular fungal communities are heterogeneous, consisting of cells experiencing different environments. Heterogeneity is likely important for the phenotypic characteristics of communities, yet it is poorly understood. Here we used colonies of the yeast Saccharomyces cerevisiae as a model fungal multicellular structure. We fractionated the outside colony layers from the cells in the center by FACS, using a Cit1-GFP marker expressed exclusively on the outside. Transcriptomics analysis of the two subpopulations revealed that the outside colony layers are actively growing by fermentative metabolism, while the cells residing on the inside are in a resting state and experience changes to mitochondrial activity. Our data shows several parallels with C. albicans biofilms providing insight into the contributions of heterogeneity to biofilm phenotypes. Hallmarks of C. albicans biofilms - the expression of ribosome and translation functions and activation of glycolysis and ergosterol biosynthesis occur on the outside of colonies, while expression of genes associates with sulfur assimilation is observed in the colony center. Cell wall restructuring occurs in biofilms, and cell wall functions are enriched in both fractions: the outside cells display enrichment of cell wall biosynthesis enzymes and cell wall proteins, while the inside cells express cell wall degrading enzymes. Our study also suggests that noncoding transcription and posttranscriptional mRNA regulation play important roles during growth of yeast in colonies, setting the scene for investigating these pathways in the development of multicellular fungal communities.
理解多细胞真菌结构对于设计针对人类真菌病原体的更好策略非常重要。例如，形成多细胞生物膜的能力是酵母白色念珠菌的关键毒力特性。白色念珠菌生物膜在留置医疗器械上形成，并且具有耐药性，在医院环境中引起严重感染。多细胞真菌群落是异质的，由经历不同环境的细胞组成。异质性可能对群落的表型特征很重要，但目前了解甚少。在这里，我们使用酵母酿酒酵母的菌落作为多细胞真菌结构的模型。我们使用仅在外部表达的 Cit1-GFP 标记物通过 FACS 从中心细胞中分离出外部菌落层。对两个亚群的转录组学分析表明，外部菌落层通过发酵代谢积极生长，而内部的细胞处于静止状态，并经历线粒体活性的变化。我们的数据显示了与白色念珠菌生物膜的几个相似之处，为生物膜表型的异质性贡献提供了深入的了解。白色念珠菌生物膜的特征-核糖体和翻译功能的表达以及糖酵解和麦角固醇生物合成的激活发生在菌落的外部，而与硫同化相关的基因表达则发生在菌落中心。生物膜中会发生细胞壁重构，细胞壁功能在两个部分中富集：外部细胞显示细胞壁生物合成酶和细胞壁蛋白的富集，而内部细胞表达细胞壁降解酶。我们的研究还表明，非编码转录和转录后 mRNA 调控在酵母在菌落中生长过程中发挥着重要作用，为研究这些途径在多细胞真菌群落的发育中的作用奠定了基础。
