Global Transcriptome Machinery Engineering

The Goal

Researchers Alper et al. (2006) were interested in creating a strain of yeast with improved ethanol tolerance and production.

The Experiment

gTME

The ethanol resistance and production phenotypes are regulated by many different genes in the yeast cell, and most of these genes are unknown. This fundamental lack of knowledge about yeast meant that the researchers could not rationally engineer the desired phenotype.

In lieu of rationally engineering the desired yeast, the team developed a new method of directed evolution, which they termed global transcriptome machinery engineering (gTME). Rather than starting with changes to an individual gene, gTME begins by creating a mutant library of a particular transcription factor. Each small change to the transcription factor resulting from mutagenesis should change the way multiple genes are expressed in a living cell. In this way, gTME would allow the researchers to test phenotypes based on changes in expression of multitudes of genes in their selection for increased ethanol tolerance and production.

A complete model of how the yeast genome relates to these phenotypes has not be described as of yet. These fact would make it ex

The researchers needed a method to test changes multiple cell-wide in yeast to engineer a strain of yeast with increased ethanol tolerance and production.

gTME

Instead of randomizing the genes for the desired phenotype themselves, most of which are unknown, the researchers chose to create a mutant library of a known transcription factor, SPT15. The team hypothesized that small changes to this transcription factor would affect gene expression cell wide in yeast. Hypothetically,

A certain mutated transcription factor, therefore, might cause upregulation certain genes and downregulation of others to form a robust new yeast cell, which could then be found in selection tests.

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