title: Reversion of a fungal genetic code alteration links proteome instability with genomic and phenotypic diversification.
abstract: Many fungi restructured their proteomes through incorporation of serine (Ser) at thousands of protein sites coded by the leucine (Leu) CUG codon. How these fungi survived this potentially lethal genetic code alteration and its relevance for their biology are not understood. Interestingly, the human pathogen Candida albicans maintains variable Ser and Leu incorporation levels at CUG sites, suggesting that this atypical codon assignment flexibility provided an effective mechanism to alter the genetic code. To test this hypothesis, we have engineered C. albicans strains to misincorporate increasing levels of Leu at protein CUG sites. Tolerance to the misincorporations was very high, and one strain accommodated the complete reversion of CUG identity from Ser back to Leu. Increasing levels of Leu misincorporation decreased growth rate, but production of phenotypic diversity on a phenotypic array probing various metabolic networks, drug resistance, and host immune cell responses was impressive. Genome resequencing revealed an increasing number of genotype changes at polymorphic sites compared with the control strain, and 80% of Leu misincorporation resulted in complete loss of heterozygosity in a large region of chromosome V. The data unveil unanticipated links between gene translational fidelity, proteome instability and variability, genome diversification, and adaptive phenotypic diversity. They also explain the high heterozygosity of the C. albicans genome and open the door to produce microorganisms with genetic code alterations for basic and applied research.
authors.affiliation: RNA Biology Laboratory, Department of Biology and Centre for Environmental and Marine Studies, University of Aveiro, 3810-193 Aveiro, Portugal.
authors.forename: Ana R
authors.initials: AR
authors.lastname: Bezerra
authors.forename: João
authors.initials: J
authors.lastname: Simões
authors.forename: Wanseon
authors.initials: W
authors.lastname: Lee
authors.forename: Johan
authors.initials: J
authors.lastname: Rung
authors.forename: Tobias
authors.initials: T
authors.lastname: Weil
authors.forename: Ivo G
authors.initials: IG
authors.lastname: Gut
authors.forename: Marta
authors.initials: M
authors.lastname: Gut
authors.forename: Mónica
authors.initials: M
authors.lastname: Bayés
authors.forename: Lisa
authors.initials: L
authors.lastname: Rizzetto
authors.forename: Duccio
authors.initials: D
authors.lastname: Cavalieri
authors.forename: Gloria
authors.initials: G
authors.lastname: Giovannini
authors.forename: Silvia
authors.initials: S
authors.lastname: Bozza
authors.forename: Luigina
authors.initials: L
authors.lastname: Romani
authors.forename: Misha
authors.initials: M
authors.lastname: Kapushesky
authors.forename: Gabriela R
authors.initials: GR
authors.lastname: Moura
authors.forename: Manuel A S
authors.initials: MA
authors.lastname: Santos
mesh_terms: D000818:Animals; D002176:Candida albicans / Q000737:chemistry / Q000235:genetics* / Q000472:pathogenicity; D003062:Codon / Q000235:genetics; D003713:Dendritic Cells / Q000737:chemistry / Q000378:metabolism; D019143:Evolution, Molecular; D005260:Female; D005656:Fungal Proteins / Q000235:genetics; D006580:Genetic Carrier Screening; D005815:Genetic Code; D014644:Genetic Variation; D016681:Genome, Fungal; D042822:Genomic Instability; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D010641:Phenotype; D020641:Polymorphism, Single Nucleotide; D020543:Proteome / Q000235:genetics*; D012331:RNA, Fungal / Q000235:genetics
chemical_list: D003062:Codon; D005656:Fungal Proteins; D020543:Proteome; D012331:RNA, Fungal
keywords: codon reassignment; evolution; tRNA