Susan Lindquist, who recently accepted the White House Medal of Science, offers new research in this week’s science on
Lindquist herself explains on the Whitehead Institute page:
“Taking what had been theory and very isolated incidents that had tremendous potential, we can help explain how organisms can rapidly acquire new traits,” says Whitehead Member Susan Lindquist. “We can show that the stress of environmental change and selective pressures can actually influence how evolutionary processes occur. And now we have a much more solid framework to hang that on.”More from Whitehead:
Whitehead Institute researchers have determined that heat shock protein 90 (Hsp90) can create heritable traits in brewer’s yeast (Saccharomyces cerevisiae) by affecting a large portion of the yeast genome. The finding has led to the conclusion that Hsp90 has played a key role in genome evolution. ..
If the protein loses its normal shape due to, for example, excessive heat, toxins or other stressors, it can no longer perform its job and may even become toxic to the cell. To provide tolerance against such stresses, cells employ a repertoire of heat-shock proteins (Hsps) that guide other proteins into their proper shape. This ancient class of proteins is present in virtually all organisms, ranging from bacteria to humans….
One of these proteins, Hsp90, is particularly abundant, comprising 1-2% of all proteins in a cell. Yet, under normal conditions, a cell uses only about 10% of its Hsp90, leaving a large reservoir of its function available should conditions suddenly turn more stressful.
Over the past several years, Lindquist has built the case that this Hsp reservoir is responsible for substantial evolutionary changes in relatively short periods of time.
From the Science release:
A Genetic “Tug-of-War” Helps Yeast Adapt:
Different strains of the budding yeast, Saccharomyces cerevisiae, can live under a wide range of environmental conditions—and a new study confirms that a particular group of molecular chaperones, known as the heat shock proteins, helps to make it all possible. Apparently, the reservoir of heat shock proteins known as Hsp90 can simultaneously act as buffer and promoter to influence the adaptive nature of the yeasts’ genetic variation. In order to reach this conclusion, Daniel Jarosz and Susan Lindquist screened 102 genetically diverse strains of the budding yeast from various ecological niches, including soil, fruit, sake, beer and infected humans. Then, the researchers measured the yeasts’ growth under a variety of conditions, including environments with alternative carbon sources, high oxidative stressors, anti-fungals, DNA-damaging agents and other molecules that are known to disrupt cellular processes. Jorosz and Lindquist used select ive molecular inhibitors to reduce the Hsp90 reservoir in the yeast and observed how the growth rates of each strain were affected. In light of their findings, the researchers suggest that the Hsp90 reservoir of proteins can promote both stasis and change simultaneously while the organism is under environmental stress. Thus, this Hsp90 system may have been influential in the evolution of the yeasts’ genomes, allowing the organisms to rapidly adapt to various environments.
Article #16: “Hsp90 and Environmental Stress Transform the Adaptive Value of Natural Genetic Variation,” by D.F. Jarosz; S. Lindquist at Whitehead Institute for Biomedical Research in Cambridge, MA; D.F. Jarosz; S. Lindquist at Howard Hughes Medical Institute in Cambridge, MA; S. Lindquist at Massachusetts Institute of Technology (MIT) in Cambridge, MA.