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Changes in levels of pyridine nucleotides during conidiogenesis in Neurospora Crassa
Conidiation in N. crassa can be either induced or suppressed by altering the growth media. When grown in standing cultures, strain Lind+ forms about 105 conidia per ml of medium. This conidial production occurs during the second to fifth day. The level of the enzyme NADase, which destroys NAD and NADP, rises more than twenty-eight fold during conidiation. At the time of peak activity of NADase, the NAD level falls to less than one-tenth the level of nonconidiating cultures, and the NADP content falls to undetectable levels. NADH and NADPH levels of conidiating cultures are slightly higher than those of nonconidiating cultures. As a consequence, the total pyridine nucleotide content of conidiating cultures is about one micromole per gram dry weight at the time the rate of conidial formation is highest, whereas it is sixty to ninety percent higher in cultures that do not form conidia. The ratio of oxidized to reduced pyridine nucleotides is greater than 1:1 when conidiation does not take place. However, during conidial formation, this ratio drops to 1:20. The effects that the altered levels of these key coenzymes could have on many areas of metabolism are considered.