Evolution through reverse transcription: a potential means to employ Lamarckian-like adaptations

Lamarck`s theory of evolution predicts that mutations will arise in response to changes in environmental conditions. Retrotransposons could mediate a realistic manifestation of Lamarckian evolution since they can insert mutations following expression. We propose here that cells could hitchhike on retrotransposon systems to speed up the evolution of expressed genes.

The Ty-retrotransposons in yeast are composed of genomic sequences integrated in the genome, which code for the machinery needed for duplication and genomic integration through reverse transcription. The translated proteins are assembled in a Viral Like particle (VLP). In the VLPs, Ty`s mRNAs are reverse transcribed into cDNA, which can be integrated back into the genome.

We hypothesize that transcribed mRNAs in a given environment may also be incorporated in the VLP compartments, and utilize the Ty system to undergo reverse transcription and genomic integration. This could result in the replacement of the original gene or integration into a different position in the genome and creation of gene retro-duplication. The high mutation rate of the reverse transcription process can speed up the evolution of genes which facilitate growth in the present environment.

We isolated VLP compartments from cells overexpressing the Ty system, and show that a selection of mRNAs of the host are found in the VLPs. We determine how exposure to different environmental conditions changes the potential of different mRNAs to be incorporated into the VLPs and undergo reverse transcription and genomic integration.