The tubulin and histone genes of Physarum polycephalum: Models for cell cycle‐regulated gene expression

Although the great majority of genes are not subject to cell-cycle controls, those that are could play a very important role in regulation of the cell cycle itself. The tubulin and histone genes of the naturally synchronous myxomycete, Physarum polycephalum, provide an excellent paradigm for such regulation. The transcription of both is highly periodic within the Physarum cycle, and curiously, both sets of genes appear to be activated at the same time. This activation appears to function as part of a developmental program, since it serves to meet future needs for each gene's product. The significance of this activation event for cell-cycle regulation is discussed with particular regard to the nature of the mitotic oscillator.