Molecular Evolution of the Candida Genetic Code
Gabriela Moura, Tatiana Lima-Costa, Laura Carreto, Ana C. Gomes and Manuel A. S. Santos
from: Candida: Comparative and Functional Genomics (Edited by: Christophe d'Enfert and Bernhard Hube). Caister Academic Press, U.K. (2007)
The leucine CUG codon is decoded as serine in many Candida species. The reassignment of this leucine codon to serine is a unique genetic event that occurred 272 +/- 25 million years ago and reprogrammed the identity of 25-30,000 CUG codons that existed in the Open Reading Frames (ORFeome) of the ancestor of yeasts. Using comparative genomics methodologies, we were able to partially reconstruct the evolutionary pathway of CUG reassignment from leucine to serine. This genetic code change had a major impact on the usage of the leucine CUN and UUA, UUG codons and forced the disappearance of most CUG codons of the Candida ancestor. In other words, the CUG codons present in extant Candida species are not related to those present in the ORFeomes of other yeasts, namely S. pombe and S. cerevisiae. Furthermore, most of these new CUG codons are located in fast evolving genes and in genes that encode small open reading frames. The genetic code of Candida species has been subjected to unique evolutionary forces whose molecular nature is not yet fully understood read more ...