title: Hsp90 prevents phenotypic variation by suppressing the mutagenic activity of transposons.
abstract: The canalization concept describes the resistance of a developmental process to phenotypic variation, regardless of genetic and environmental perturbations, owing to the existence of buffering mechanisms. Severe perturbations, which overcome such buffering mechanisms, produce altered phenotypes that can be heritable and can themselves be canalized by a genetic assimilation process. An important implication of this concept is that the buffering mechanism could be genetically controlled. Recent studies on Hsp90, a protein involved in several cellular processes and development pathways, indicate that it is a possible molecular mechanism for canalization and genetic assimilation. In both flies and plants, mutations in the Hsp90-encoding gene induce a wide range of phenotypic abnormalities, which have been interpreted as an increased sensitivity of different developmental pathways to hidden genetic variability. Thus, Hsp90 chaperone machinery may be an evolutionarily conserved buffering mechanism of phenotypic variance, which provides the genetic material for natural selection. Here we offer an additional, perhaps alternative, explanation for proposals of a concrete mechanism underlying canalization. We show that, in Drosophila, functional alterations of Hsp90 affect the Piwi-interacting RNA (piRNA; a class of germ-line-specific small RNAs) silencing mechanism leading to transposon activation and the induction of morphological mutants. This indicates that Hsp90 mutations can generate new variation by transposon-mediated 'canonical' mutagenesis.
authors.affiliation: Dipartimento di Scienze e Tecnologie Biologiche ed Ambientali (DiSTeBA), University of Salento, 73100 Lecce, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Specchia
authors.forename: Lucia
authors.initials: L
authors.lastname: Piacentini
authors.forename: Patrizia
authors.initials: P
authors.lastname: Tritto
authors.forename: Laura
authors.initials: L
authors.lastname: Fanti
authors.forename: Rosalba
authors.initials: R
authors.lastname: D'Alessandro
authors.forename: Gioacchino
authors.initials: G
authors.lastname: Palumbo
authors.forename: Sergio
authors.initials: S
authors.lastname: Pimpinelli
authors.forename: Maria P
authors.initials: MP
authors.lastname: Bozzetti
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D015139:Blotting, Southern; D004251:DNA Transposable Elements / Q000235:genetics*; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism*; D005260:Female; D020868:Gene Silencing / Q000187:drug effects; D014644:Genetic Variation / Q000235:genetics*; D005838:Genotype; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006720:Homozygote; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D008969:Molecular Sequence Data; D016296:Mutagenesis / Q000235:genetics*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D011494:Protein Kinases / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D016227:Benzoquinones; D004251:DNA Transposable Elements; D029721:Drosophila Proteins; D018841:HSP90 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C089272:Hsp83 protein, Drosophila; D047029:Lactams, Macrocyclic; D050505:Mutant Proteins; D034741:RNA, Small Interfering; D011494:Protein Kinases; C094331:Ste protein, Drosophila; C001277:geldanamycin