The 25S′ to 25S processing function of Dxo1 arose after duplication of Dxo1 and Rai1. (A) Dxo1 and Rai1 are duplicated in Saccharomyces and Kluyveromyces, but not in Wickerhamomyces or Cyberlindnera, suggesting that duplication occurred in the common ancestor of Saccharomyces and Kluyveromyces after divergence form the other two species. (B) Rai1 function is more ancient than the duplication. Shown is a growth assay of a rai1Δ strain that expresses Rai1 or Dxo1 homologs (from plasmids pRS416, pAv1820, pAv1804, pAv1814, pAv1819, pAv1821, and pAv1815 from top to bottom). The nonduplicated genes from Wickerhamomyces and Cyberlindnera complement indicating that the Rai1 function already existed before duplication. Shown is a representative growth assay from biological duplicates. (C) Dxo1 function arose after the duplication. The dxo1Δ strain was transformed with pRS416, pAv1804, pAv1820, pAv1819, pAv1814, pAv1821, and pAv1815 (from left to right). Shown is a representative northern blot of the 25S′ rRNA and the RNA subunit of the signal recognition particle (SRP; loading control) and the quantitation of two biological replicates.
