酿酒酵母孢子在出生时就被预先极化,以便从孢子-孢子连接处向外生长,并穿透子囊壁。
Saccharomyces spores are born prepolarized to outgrow away from spore-spore connections and penetrate the ascus wall.
机构信息
Cell and Developmental Biology, University of Colorado Anschutz Medical Campus, Aurora, Colorado, USA.
Environmental Health and Radiological Sciences, Colorado State University, Fort Collins, Colorado, USA.
出版信息
Yeast. 2021 Jan;38(1):90-101. doi: 10.1002/yea.3540. Epub 2020 Dec 7.
How nonspore haploid Saccharomyces cells choose sites of budding and polarize towards pheromone signals in order to mate has been a subject of intense study. Unlike nonspore haploids, sibling spores produced via meiosis and sporulation by a diploid cell are physically interconnected and encased in a sac derived from the old cell wall of the diploid, called the ascus. Nonspore haploids bud adjacent to previous sites of budding, relying on stable cortical landmarks laid down during prior divisions, but because spore membranes are made de novo, it was assumed that, as is known for fission yeast, Saccharomyces spores break symmetry and polarize at random locations. Here, we show that this assumption is incorrect: Saccharomyces cerevisiae spores are born prepolarized to outgrow, prior to budding or mating, away from interspore bridges. Consequently, when spores bud within an intact ascus, their buds locally penetrate the ascus wall, and when they mate, the resulting zygotes adopt a unique morphology reflective of repolarization towards pheromone. Long-lived cortical foci containing the septin Cdc10 mark polarity sites, but the canonical bud site selection programme is dispensable for spore polarity, thus the origin and molecular composition of these landmarks remain unknown. These findings demand further investigation of previously overlooked mechanisms of polarity establishment and local cell wall digestion and highlight how a key step in the Saccharomyces life cycle has been historically neglected.
非孢子单倍体细胞如何选择出芽位点,并朝着交配的信息素信号极化,一直是一个研究热点。与非孢子单倍体细胞不同,通过二倍体细胞减数分裂和孢子形成产生的同胞孢子在物理上是相互连接的,并被包裹在一个由二倍体细胞的旧细胞壁衍生而来的囊(称为子囊)中。非孢子单倍体细胞在相邻的出芽位点出芽,依赖于在先前的分裂过程中形成的稳定皮质标记,但由于孢子膜是从头合成的,因此人们假设,正如裂殖酵母所知,酵母孢子会在随机位置打破对称并极化。在这里,我们表明这种假设是不正确的:酿酒酵母孢子在出芽或交配之前就已经预先极化,以从孢子间桥处向外生长。因此,当孢子在完整的子囊中出芽时,它们的芽局部穿透子囊壁,当它们交配时,产生的合子采用独特的形态,反映出朝向信息素的重新极化。含有 septin Cdc10 的长寿皮质焦点标记极性位点,但经典的芽位点选择程序对于孢子极性是可有可无的,因此这些标记的起源和分子组成仍然未知。这些发现要求进一步研究以前被忽视的极性建立和局部细胞壁消化机制,并强调了酿酒酵母生命周期中的一个关键步骤是如何被历史忽视的。
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