Specific regulatory interconnection between the leucine and histidine pathways of Neurospora crassa

Abstract

Leucine auxotrophs of Neurospora fall into two discrete categories with respect to sensitivity to the herbicide, 3-amino-1,2,4-triazole. The pattern of resistance corresponds exactly to the ability to produce the leucine pathway control elements, alpha-isopropylmalate and the leu-3 product. An analysis of the regulatory response of the production of enzymes of histidine biosynthesis to alpha-isopropylmalate implicates the control elements of the leucine pathway as important components of the mechanism governing the production of the target enzyme of aminotriazole inhibition, imidazoleglycerol-phosphate dehydratase (EC 4.2.1.19). The evidence suggests that the regulatory interconnection between the two pathways is direct and is independent of other general integrating regulatory mechanisms which appear to be operative in both pathways. A general method for isolating leu-1 and leu-2, as well as other regulatory mutants, is described, which takes advantage of the specificity of the resistance to the inhibitor. Use of analogous systems is prescribed for the analysis of other regulatory interconnections which, like this one, might not be anticipated directly from structural or biosynthetic considerations.

3-Amino-1,2,4-triazole Prolongs Carnation Vase Life

“…Aminotriazole (ATA), a lowmolecular-weight heterocyclic ring compound, is currently marketed under its common name (amitrole or amizole) for use as a postemergence, nonselective, systemic herbicide. The spectrum of ATA's effects on cellular metabolism is broad and may include inhibition of catalase activity (Margoliash et al, 1960), purine biosynthesis (Lenton, 1987), mitochondrial protein biosynthesis, and imidazol-glycerol-phosphate dehydratase activity, an essential enzyme in the histidine biosynthetic pathway of bacteria and fungi (Kidd and Gross, 1984). We report here that ATA inhibits both physiological and morphological aspects of floral senescence in carnations and may serve as an alternative floral preservative for camations and other cut flowers.…”

Inhibition of Ethylene Biosynthesis and Action in Cut Carnations (Dianthus caryophyllus L.) by Aminotriazole

“…Aminotriazole, a low-molecular-weight heterocyclic ring compound used as a postemergence, nonselective, systemic herbicide (Sine et al, 1991), may be useful in identifying the molecular species involved in ethylene-receptor interaction or signal transduction of ethylene action. The effects of aminotriazole on cellular metabolism include inhibition of peroxisomal assembly of tetrameric catalase apoenzyme (Reid et al, 1981), CO 2 assimilation (Amory et al, 1992), mitochondrial protein biosynthesis, and imidazolglycerol-phosphate dehydratase, an enzyme of histidine biosynthesis in bacteria and fungi (Kidd and Gross, 1984). However, aminotriazole is not a nonspecific metabolic poison, since it does not inhibit enzymes such as ascorbate peroxidase and glutathione reductase (Amory et al, 1992).…”