True H L, Lindquist S L
Department of Molecular Genetics and Cell Biology, Howard Hughes Medical Institute, The University of Chicago, Illinois 60637, USA.
Nature. 2000 Sep 28;407(6803):477-83. doi: 10.1038/35035005.
A major enigma in evolutionary biology is that new forms or functions often require the concerted effects of several independent genetic changes. It is unclear how such changes might accumulate when they are likely to be deleterious individually and be lost by selective pressure. The Saccharomyces cerevisiae prion [PSI+] is an epigenetic modifier of the fidelity of translation termination, but its impact on yeast biology has been unclear. Here we show that [PSI+] provides the means to uncover hidden genetic variation and produce new heritable phenotypes. Moreover, in each of the seven genetic backgrounds tested, the constellation of phenotypes produced was unique. We propose that the epigenetic and metastable nature of [PSI+] inheritance allows yeast cells to exploit pre-existing genetic variation to thrive in fluctuating environments. Further, the capacity of [PSI+] to convert previously neutral genetic variation to a non-neutral state may facilitate the evolution of new traits.
进化生物学中的一个主要谜团是，新的形式或功能通常需要几个独立基因变化的协同作用。目前尚不清楚当这些变化单独存在时可能有害并因选择压力而丢失的情况下，它们是如何积累的。酿酒酵母朊病毒[PSI+]是翻译终止保真度的一种表观遗传修饰因子，但其对酵母生物学的影响尚不清楚。在此我们表明，[PSI+]提供了揭示隐藏遗传变异并产生新的可遗传表型的方法。此外，在所测试的七个遗传背景中的每一个中，所产生的表型组合都是独特的。我们提出，[PSI+]遗传的表观遗传和亚稳态性质使酵母细胞能够利用预先存在的遗传变异在波动的环境中茁壮成长。此外，[PSI+]将先前中性的遗传变异转化为非中性状态的能力可能会促进新性状的进化。
