title: Hsp90 as a capacitor for morphological evolution.
abstract: The heat-shock protein Hsp90 supports diverse but specific signal transducers and lies at the interface of several developmental pathways. We report here that when Drosophila Hsp90 is mutant or pharmacologically impaired, phenotypic variation affecting nearly any adult structure is produced, with specific variants depending on the genetic background and occurring both in laboratory strains and in wild populations. Multiple, previously silent, genetic determinants produced these variants and, when enriched by selection, they rapidly became independent of the Hsp90 mutation. Therefore, widespread variation affecting morphogenic pathways exists in nature, but is usually silent; Hsp90 buffers this variation, allowing it to accumulate under neutral conditions. When Hsp90 buffering is compromised, for example by temperature, cryptic variants are expressed and selection can lead to the continued expression of these traits, even when Hsp90 function is restored. This provides a plausible mechanism for promoting evolutionary change in otherwise entrenched developmental processes.
authors.affiliation: Howard Hughes Medical Institute, University of Chicago, Illinois 60637, USA.
authors.forename: S L
authors.initials: SL
authors.lastname: Rutherford
authors.forename: S
authors.initials: S
authors.lastname: Lindquist
mesh_terms: D000818:Animals; D019020:Directed Molecular Evolution; D004330:Drosophila / Q000033:anatomy & histology / Q000235:genetics / Q000502:physiology; D029721:Drosophila Proteins; D014644:Genetic Variation; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000502:physiology*; D006360:Heat-Shock Proteins / Q000235:genetics; D008957:Models, Genetic; D009154:Mutation; D010641:Phenotype; D013696:Temperature
chemical_list: D029721:Drosophila Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C089272:Hsp83 protein, Drosophila