BACKGROUND:
Spore germination in the
yeast Saccharomyces cerevisiae is a process in which non-dividing
haploid spores re-enter the
mitotic cell cycle and resume vegetative growth. To study the signals and pathways underlying
spore germination we examined the global changes in
gene expression and followed
cell-cycle and germination markers during this process. RESULTS: We find that the germination process can be divided into two distinct stages. During the first stage, the induced
spores respond only to
glucose. The transcription program during this stage recapitulates the general transcription response of
yeast cells to
glucose. Only during the second phase are the cells able to
sense and respond to other nutritional components in the environment. Components of the
mitotic machinery are involved in
spore germination but in a distinct pattern. In contrast to the
mitotic cell cycle, growth-related events during germination are not coordinated with nuclear events and are separately regulated. Thus, genes that are co-induced during G1/S of the
mitotic cell cycle, the dynamics of the
septin Cdc10 and the kinetics of accumulation of the
cyclin Clb2 all exhibit distinct patterns of regulation during
spore germination, which allow the separation of
cell growth from nuclear events. CONCLUSION: Taken together, genome-wide expression profiling enables us to follow the progression of
spore germination, thus dividing this process into two major stages, and to identify germination-specific regulation of components of the
mitotic cell cycle machinery.
