Unique Properties of the S. cerevisiae Spore Wall and Its Applications

Abstract

When diploid cells of the budding yeast Saccharomyces cerevisiae are incubated under starvation conditions, they differentiate into a dormant and stress-resistant form of haploid cells termed spores. Spores have a cell wall (spore wall) which is more complex than that of vegetative cells. The spore wall is composed of the following layers, from inside to outside: mannan, glucan, chitosan, and dityrosine. While the inner two layers contain shared components between the vegetative cell wall and spore wall, chitosan and dityrosine are unique components of the spore wall. The outer two layers are dispensable for the viability of spores. However, the unique features of these layers endow spores with distinct properties, such as stress resistance. Some of these properties allow spores to be used for beneficial purposes. For example, removal of the dityrosine layer by genetic manipulation leads to exposure of the chitosan layer on the spore surface; such mutant spores can be used as chitosan particles. Furthermore, spores can retain soluble secretory proteins in the spore wall because the dityrosine layer works as a diffusion barrier. Thus, if secretory forms of enzymes are expressed in sporulating cells, the enzymes are entrapped in the spore wall. Spores containing enzymes in the spore wall can be used as enzyme capsules.