In both of these scenarios, consumption of the Hsp90 reservoir by environmental stress allows numerous traits to be exhibited or lost immediately and simultaneously. If the new phenotype is beneficial for this stressful environment, the organism will survive. Because the new phenotypes are based on genetic variation they can be passed on to the next generation and evolution progresses. If the traits are detrimental, the organism will not survive and its traits will die with it.
This method of suddenly unveiling a new phenotype consisting of multiple traits could also explain the evolution of interdependent traits that are detrimental on their own. Such a seeming leap forward in evolution has puzzled biologists since Darwin.
Although earlier evidence indicated that Hsp90 activity could affect evolution, a Lindquist postdoctoral researcher, Daniel Jarosz, wanted to understand mechanistically Hsp90's effects on one species and provide solid evidence for Hsp90's impact on evolution.
In the Science paper, first author Jarosz analyzed the effects of Hsp90 on 102 genetically diverse strains of brewer's yeast by placing them under various stressful conditions and inhibiting Hsp90. All of the strains had substantial growth changes in specific conditions.
Jarosz then learned more about the Hsp90-affected traits by crossing two strains and looking at the progeny. He determined that about half of the traits affected by Hsp90 were positive and half were negative. Also, reducing Hsp90 in several of the crossed strains' progeny revealed multiple interdependent traits.
To see how much Hsp90 affects the phenotypes of yeast strains, Jarosz looked at the genetic sequences of 48 strains and compared the genotypes to the phenotypes that he saw in those strains. When Hsp90 functioned normally, the genotype and phenotype weakly re
|Contact: Nicole Giese|
Whitehead Institute for Biomedical Research