Karyogamy-dependent enzyme derepression in the basidiomycete [formula omitted

Abstract

Observation of stained nuclei coupled with determination of activity of NADP-linked glutamate dehydrogenase (NADP-GDH) in the same tissue, showed that increase in enzyme activity was initiated as karyogamy became evident in normally-developing fruit bodies of the basidiomycete Coprinus cinereus . Enzyme activity stabilised for about 4 hours during meiosis, but resumed after meiosis II, and continued to increase until spore maturation. When the time of exposure to light was varied, karyogamy occurred only in tissues which received at least 24 h light exposure and, most significantly, derepression of NADP-GDH was apparent at the time of or very soon after karyogamy. It is concluded that expression of NADP-GDH in the fruit body cap of Coprinus cinereus is either a component part of the cellular programme involved in karyogamy, or is directly triggered by that programme. Parallel assays showed that protein content of fruit body cap tissue declined during development; the decline started before meiosis and also arrested during the division. A major flux in cyclic-AMP content occurred at a much earlier stage, a large accumulation in fruit body initials being rapidly reduced as these developed into primordia. Levels of cAMP similar to those recorded in vegetative cells were approached prior to meiosis, suggesting that this nucleotide has little involvement in development of the fruit body after formation of initials. Onset of large-scale utilization of accumulated glycogen proved to be a post-meiotic event.