Control of nitrogen catabolite repression is not affected by the tRNA(Gln-CUU) mutation, which results in constitutive pseudohyphal growth of Saccharomyces cerevisiae

Saccharomyces cerevisiae responds to nitrogen availability in several ways. (1) The cell is able to distinguish good nitrogen sources from poor ones t hrough a process designated nitrogen catabolite repression (NCR). Good and poor nitrogen sources do not demonstrably affect the cell cycle other than to influence the cell's doubling time. (ii) Nitrogen starvation promotes th e initiation of sporulation and pseudohyphal growth. (iii) Nitrogen starvat ion strongly affects the cell cycle; nitrogen-starved cells arrest in G(1). A specific allele of the SUP70/CDC65 tRNA(Gln) gene (sup70-65) has been re ported to be defective in nitrogen signaling associated with pseudohyphal f ormation, sporulation, and NCR, Our data confirm that pseudohyphal growth o ccurs gratuitously in sup70-65 mutants cultured in nitrogen-rich medium at 30 degrees C. However, we find neither any defect in NCR in the sup70-65 mu tant nor any alteration in the control of YVH1 expression, which has been p reviously shown to be specifically induced by nitrogen starvation.