Sequential Logic of Polarity Determination during the Haploid-to-Diploid Transition in Saccharomyces cerevisiae
Sequential Logic of Polarity Determination during the Haploid-to-Diploid Transition in Saccharomyces cerevisiae
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DOI：
10.1128/ec.00161-14
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发表时间：
2014-11-01
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影响因子：
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通讯作者：
Tartakoff, Alan Michael
中科院分区：
文献类型：
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作者：
Rinonos, Serendipity Zapanta;Rai, Urvashi;Tartakoff, Alan Michael
在许多生物体中，单倍体生殖细胞相遇的几何形状是任意的。在酿酒酵母中，已经看到所得的合子在产生二倍体后代时在几个方向上不对称地出芽。什么样的机制决定了方向的选择，以及指导极性的机制是否会随着时间的推移而改变？不同的皮质“地标”蛋白亚群引导单倍体与二倍体细胞出芽，这两种细胞都需要Bud 1/Rsr 1 GTbind将地标与肌动蛋白连接起来。我们观察到，作为交配对的单倍体细胞形成合子，芽位规范的进展，通过三个阶段。第一阶段是蛋白质的分解和有限的分散，集中在细胞接触区，然后重新组装，产生一个大的中间芽。初始芽的内侧放置不需要芽1。第二阶段产生一个连续的芽，并取决于轴向标志。随着Axl 1标志滴度的降低，第三阶段最终将出芽重定向到末端位点，并由双极标志促进。因此，在最初的随机遭遇，指定内侧出芽，顺序的空间选择是由一个单一的皮质决定因素，决定是否连续芽将毗邻其前身的滴度编排。
In many organisms, the geometry of encounter of haploid germ cells is arbitrary. In Saccharomyces cerevisiae, the resulting zygotes have been seen to bud asymmetrically in several directions as they produce diploid progeny. What mechanisms account for the choice of direction, and do the mechanisms directing polarity change over time? Distinct subgroups of cortical "landmark" proteins guide budding by haploid versus diploid cells, both of which require the Bud1/Rsr1 GTPase to link landmarks to actin. We observed that as mating pairs of haploid cells form zygotes, bud site specification progresses through three phases. The first phase follows disassembly and limited scattering of proteins that concentrated at the zone of cell contact, followed by their reassembly to produce a large medial bud. Bud1 is not required for medial placement of the initial bud. The second phase produces a contiguous bud(s) and depends on axial landmarks. As the titer of the Axl1 landmark diminishes, the third phase ultimately redirects budding toward terminal sites and is promoted by bipolar landmarks. Thus, following the initial random encounter that specifies medial budding, sequential spatial choices are orchestrated by the titer of a single cortical determinant that determines whether successive buds will be contiguous to their predecessors.