Abstract

The yeast Nadsonia fulvescens is characterized by a unique life cycle. After conjugation between the parent cell and the first bud, the zygote moves into a second bud formed at the opposite end of the parent cell. This second bud is then delimited by a septum and becomes the ascus. Usually one, rarely two spherical, brownish, spiny to warty ascospores are formed within the ascus giving rise to brown coloured colonies. Strikingly, no increased mitochondrial activity was observed in the ascus when compared to the vegetative cells as previously reported for many yeast. In this study, the parent cell and attached first bud showed increased mitochondrial activity when compared to the ascus. When anti-mitochondrial compounds were added, the mitochondrial activity was inhibited in the parent cell and attached first bud followed by the formation of less asci with ascospores (many not fully developed and white coloured giving rise to white colonies). We conclude that sufficient mitochondrial activity in the parent cell and first bud is necessary to produce enough energy for the formation of a proper ascus with brown coloured ascospore (s).  

Key words: Asci, ascospore, life cycle, mitochondria, mitochondrial inhibitors,Nadsonia fulvescens.