title: Growth regulation by GTP. Regulation of nucleotide pools in Neurospora by nitrogen and sulfur control systems.
abstract: Purine nucleotide pools in the fungus Neurospora crassa decline in response to carbon, nitrogen, or sulfur deprivation. There is, in addition, a decline in GTP/ATP ratios on nitrogen or sulfur deprivation in wild type. The GTP/ATP decline is missing on nitrogen deprivation of the nitrogen control mutant, nit-2, and on sulfur deprivation of the sulfur control mutant, cys-3. The nit-2 mutant also shows elevated UTP pools on nitrogen deprivation when compared with similarly treated wild type. Six-hour sulfur-deprived cys-3 shows multiple aberrations in nucleotide pools when compared with similarly treated wild type. These include very low energy charge and depletion of pools of most nucleotides. ATP in sulfur-deprived cys-3 drops by about 88%. Sulfur-deprived cys-3 is also greatly impaired in comparison with wild type in its ability to resume growth when restored to nutritional sufficiency after a period of sulfur deprivation. These results clearly demonstrate that the nitrogen (nit-2) and sulfur (cys-3 regulatory systems are not limited to control of catabolism of exogenous nitrogen and sulfur sources, respectively, but rather influence, a broader range of cellular properties than has been previously thought. The pattern of GTP pool control is consistent with a positive role for GTP in growth control. Evidence in other systems supporting such a growth-regulating role for GTP is discussed.
authors.affiliation: Washington State University, Pullman 99164-4350.
authors.forename: M L
authors.initials: ML
authors.lastname: Pall
authors.forename: C K
authors.initials: CK
authors.lastname: Robertson
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D009491:Neurospora / Q000378:metabolism*; D009492:Neurospora crassa / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*
chemical_list: D013455:Sulfur; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D008715:Methionine; D009584:Nitrogen