Institut Pasteur, Université Paris Cité, CNRS UMR3525, Genétique des Génomes, Paris F-75015, France.
Present address: Abolis Biotechnologies, 5 Rue Henri Desbruères, Evry 91030, France.
Genetics. 2022 May 5;221(1). doi: 10.1093/genetics/iyac042.
Megasatellites are large tandem repeats found in all fungal genomes but especially abundant in the opportunistic pathogen Candida glabrata. They are encoded in genes involved in cell-cell interactions, either between yeasts or between yeast and human cells. In the present work, we have been using an iterative genetic system to delete several Candida glabrata megasatellite-containing genes and found that 2 of them were positively involved in adhesion to epithelial cells, whereas 3 genes negatively controlled adhesion. Two of the latter, CAGL0B05061g or CAGL0A04851g, were also negative regulators of yeast-to-yeast adhesion, making them central players in controlling Candida glabrata adherence properties. Using a series of synthetic Saccharomyces cerevisiae strains in which the FLO1 megasatellite was replaced by other tandem repeats of similar length but different sequences, we showed that the capacity of a strain to flocculate in liquid culture was unrelated to its capacity to adhere to epithelial cells or to invade agar. Finally, to understand how megasatellites were initially created and subsequently expanded, an experimental evolution system was set up, in which modified yeast strains containing different megasatellite seeds were grown in bioreactors for more than 200 generations and selected for their ability to sediment at the bottom of the culture tube. Several flocculation-positive mutants were isolated. Functionally relevant mutations included general transcription factors as well as a 230-kbp segmental duplication.
大片段卫星重复序列是所有真菌基因组中都存在的大型串联重复序列，但在机会性病原体光滑念珠菌中尤为丰富。它们编码在参与细胞间相互作用的基因中，无论是酵母之间还是酵母与人类细胞之间。在本工作中，我们使用迭代遗传系统来删除几个含有光滑念珠菌大片段卫星重复序列的基因，发现其中 2 个基因正向参与与上皮细胞的黏附，而 3 个基因负调控黏附。其中的 2 个基因，CAGL0B05061g 或 CAGL0A04851g，也是酵母间黏附的负调控因子，使它们成为控制光滑念珠菌黏附特性的核心因子。使用一系列合成的酿酒酵母菌株，其中 FLO1 大片段卫星重复序列被其他相似长度但不同序列的串联重复序列取代，我们表明，菌株在液体培养中絮凝的能力与其黏附上皮细胞或侵袭琼脂的能力无关。最后，为了了解大片段卫星重复序列是如何最初产生并随后扩展的，建立了一个实验进化系统，其中含有不同大片段卫星种子的改良酵母菌株在生物反应器中生长超过 200 代，并选择其在培养管底部沉淀的能力。分离出了几个絮凝阳性突变体。功能相关的突变包括一般转录因子以及 230kbp 的片段重复。
