ABSTRACT
The secretory pathway mediates the localization of most nascent proteins to the vacuole, plasma membrane, or for excretion. Resident luminal proteins of the endoplasmic reticulum are transferred to the Golgi apparatus, presumably adventitiously. The ERD2 structural gene encodes a receptor that is responsible for the retrieval of these proteins. The chapter shows that some genes, ERG3 and ERG6, that have been designated as nonessential, are in fact essential under some growth conditions. Ecologically, yeast cells “show a marked preference for sugary micro-habitats, usually of vegetable origin. Their ability to develop anaerobically, together with the inability of most other fungi to tolerate the alcohol produced, enables yeasts to compete successfully for those habitats.” Representatives of Saccharomyces have been isolated from sugar cane, sorghum, honey, maple syrup, soft Italian cheeses, extracts of peppermint, exudations of oaks and elms, and fruits, such as grapes, figs, apples, holly berries, etc.
