An analysis of codon bias in six red yeast species.

Red yeasts, primarily species of Rhodotorula, Sporobolomyces, and other genera of Pucciniomycotina, are traditionally considered proficient systems for lipid and terpene production, and only recently have also gained consideration for the production of a wider range of molecules of biotechnological potential. Improvements of transgene delivery protocols and regulated gene expression systems have been proposed, but a dearth of information on compositional and/or structural features of genes has prevented transgene sequence optimization efforts for high expression levels. Here, the codon compositional features of genes in six red yeast species were characterized, and the impact that evolutionary forces may have played in shaping this compositional bias was dissected by using several computational approaches. Results obtained are compatible with the hypothesis that mutational bias, although playing a significant role, cannot alone explain synonymous codon usage bias of genes. Nevertheless, several lines of evidences indicated a role for translational selection in driving the synonymous codons that allow high expression efficiency. These optimal synonymous codons are identified for each of the six species analyzed. Moreover, the presence of intragenic patterns of codon usage, which are thought to facilitate polyribosome formation, was highlighted. The information presented should be taken into consideration for transgene design for optimal expression in red yeast species.