title: Chimeric protein complexes in hybrid species generate novel phenotypes.
abstract: Hybridization between species is an important mechanism for the origin of novel lineages and adaptation to new environments. Increased allelic variation and modification of the transcriptional network are the two recognized forces currently deemed to be responsible for the phenotypic properties seen in hybrids. However, since the majority of the biological functions in a cell are carried out by protein complexes, inter-specific protein assemblies therefore represent another important source of natural variation upon which evolutionary forces can act. Here we studied the composition of six protein complexes in two different Saccharomyces "sensu stricto" hybrids, to understand whether chimeric interactions can be freely formed in the cell in spite of species-specific co-evolutionary forces, and whether the different types of complexes cause a change in hybrid fitness. The protein assemblies were isolated from the hybrids via affinity chromatography and identified via mass spectrometry. We found evidence of spontaneous chimericity for four of the six protein assemblies tested and we showed that different types of complexes can cause a variety of phenotypes in selected environments. In the case of TRP2/TRP3 complex, the effect of such chimeric formation resulted in the fitness advantage of the hybrid in an environment lacking tryptophan, while only one type of parental combination of the MBF complex allowed the hybrid to grow under respiratory conditions. These phenotypes were dependent on both genetic and environmental backgrounds. This study provides empirical evidence that chimeric protein complexes can freely assemble in cells and reveals a new mechanism to generate phenotypic novelty and plasticity in hybrids to complement the genomic innovation resulting from gene duplication. The ability to exchange orthologous members has also important implications for the adaptation and subsequent genome evolution of the hybrids in terms of pattern of gene loss.
authors.affiliation: Faculty of Life Sciences, Michael Smith Building, University of Manchester, Manchester, United Kingdom.
authors.forename: Elzbieta M
authors.initials: EM
authors.lastname: Piatkowska
authors.forename: Samina
authors.initials: S
authors.lastname: Naseeb
authors.forename: David
authors.initials: D
authors.lastname: Knight
authors.forename: Daniela
authors.initials: D
authors.lastname: Delneri
mesh_terms: D000483:Alleles; D000878:Anthranilate Synthase / Q000235:genetics*; D019143:Evolution, Molecular; D016678:Genome; D006824:Hybridization, Genetic; D007209:Indole-3-Glycerol-Phosphate Synthase / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D010446:Peptide Fragments / Q000235:genetics*; D010641:Phenotype; D011993:Recombinant Fusion Proteins / Q000235:genetics*; D012440:Saccharomyces / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*
chemical_list: D008565:Membrane Proteins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; C500290:peptide SVYDFFVWL; D007209:Indole-3-Glycerol-Phosphate Synthase; D000878:Anthranilate Synthase; C087439:TRP3 protein, S cerevisiae