The Use of Yeast in Biosensing

Abstract

Yeast has been used as a model for several diseases as it is the simplest unicellular eukaryote, safe and easy to culture and harbors most of the fundamental processes that are present in almost all higher eukaryotes, including humans. From understanding the pathogenesis of disease to drug discovery studies, yeast has served as an important biosensor. It is not only due to the conservation of genetics, amenable modification of its genome and easily accessible analytical methods, but also some characteristic features such as its ability to survive with defective mitochondria, making it a highly flexible microbe for designing whole-cell biosensing systems. The aim of this review is to report on how yeasts have been utilized as biosensors, reporting on responses to various stimuli.

Keywords: FRET; biosensor; fluorescent proteins; yeast; yeast reporters; yeast surface display; yeast two-hybrid.

Figure 1

The classical yeast two-hybrid system for biosensing protein interactions in vivo. (A) shows there is no transcription of the reporter gene if there is no interaction between the proteins of interest X and Y; (B) shows that when there is an interaction of proteins X and Y, this leads to the recruitment of RNA polymerase II to the promoter region and activates the promoter for expression of the downstream reporter gene.

Figure 2

Three types of yeast surface displays that have been used in the past. (a) represents the classical yeast surface display with glycosylphosphatidylinositol (GPI) dependent anchor fused with the protein of interest (POI); (b) shows GPI independent anchor fusion with POI displayed in the cell surface; (c) shows co-display of multiple POIs on the cell surface using the GPI dependent strategy.

Figure 3

Chemical reaction involved in the β-galactosidase assay showing conversion of o-nitrophenyl-galactoside (ONPG) to o-nitrophenol and galactose. The o-nitrophenol produced can be quantified using colorimetry to measure absorbance at 420 nm wavelength.

Figure 4

Emission ranges of some fluorescent proteins (TagBFP, EGFP, mCherry, and iRFP720) with fewer overlapping regions for designing a multi-colored biosensor in yeast.

Figure 5

Yeast reporter constructs used in the study of neurodegenerative diseases. Different fluorescent proteins have been tagged at both N- and C-termini of the proteins of interest. The effect of tagging the target proteins of interest could be different depending upon the species of fusion protein. The promoters can be both constitutive or inducible based on the final application or goal of the study. A secretion signal can precede the fusion protein sequences if the ER processing of the fusion protein is required.

Figure 6

Plasmid map for the heat shock response reporter pYHSRed1 designed to express mCherry fluorescent protein as a reporter protein that expresses under control of a heat shock promoter, a promoter from heat shock protein 42 (HSP42) containing the heat shock elements (HSEs).

Figure 7

Excitation–Emission of the FRET donor (green curves) and FRET acceptor (blue curves) showing substantial overlap (shaded light green) in the range between FRET donor emission and FRET acceptor excitation. ExD, FRET donor excitation range; EmD, FRET donor emission range; ExA, FRET acceptor excitation range; and EmA, FRET acceptor emission range.

Figure 8

Schematic diagram showing yeast biosensor design for detecting pollutants. The system will sense the presence of the pollutants using pollutant sensing elements in the promoter of the biosensor design that enables expression of a downstream reporter gene.