Developmental regulation of nicotinamide adenine dinucleotide (phosphate) glycohydrolase in Neurospora crassa.

The formation of nicotinamide adenine dinucleotide (phosphate) glycohydrolase [NAD(P)ase; EC 3.2.2.6] in Neurospora crassa was found to be both spatially and temporally programmed. Ascospores were devoid of the enzyme. Vegetative hyphae contained little or no NADase activity. During the differentiation of aerial cell types (aerial hyphae and macroconidia), the specific activity of the enzyme increased by at least three orders of magnitude. Although transiently associated with young aerial hyphae, the enzyme became an integral and stable part of the mature macroconidia. NAD(P)ase could also be “derepressed” under conditions that permitted aerialogenesis in the absence of conidiation. The increase in the specific activity of NAD(P)ase during cell differentiation required concomitant RNA and protein synthesis; in vitro mixing experiments revealed no cell-specific activators or inhibitors of enzyme activity. The temperature-critical period for the in vitro inactivation of a temperature-sensitive enzyme variant was restricted to the period of actual enzyme expression.The data reported in this paper combined with data reported in a previous paper (Nelson et al., 1975b) underscore an important distinction in studies of development, namely, developmental regulation of a macromolecule versus regulation of development by a macromolecule. This paper provides evidence that NAD(P)ase is developmentally regulated. The previous paper provides evidence that the appearance of this enzyme need not regulate development.