文档介绍：articles
A yeast prion provides a mechanism for
ic variation and phenotypic
diversity
Heather L. True & Susan L. Lindquist
Department of Molecular ics and Cell Biology, Howard Hughes Medical Institute, The University of Chicago, Chicago, Illinois 60637, USA
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A major enigma in evolutionary biology is that new forms or functions often require the concerted effects of several independent
ic changes. It is unclear how such changes might accumulate when they are likely to be deleterious individually and be lost
by selective pressure. The haromyces cerevisiae prion [PSI+] is an ic modi®er of the ®delity of translation termination,
but its impact on yeast biology has been unclear. Here we show that [PSI+] provides the means to uncover hidden ic variation
and produce new heritable phenotypes. Moreover, in each of the seven ic backgrounds tested, the constellation of
phenotypes produced was unique. We propose that the ic and metastable nature of [PSI+] inheritance allows yeast cells to
exploit pre-existing ic variation to thrive in ¯uctuating environments. Further, the capacity of [PSI+] to convert previously