Analysis of the pdx-1 (snz-1/sno-1) Region of the Neurospora crassa Genome: Correlation of Pyridoxine-Requiring Phenotypes With Mutations in Two Structural Genes

Genetics, Vol. 157, pp. 1067-1075

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Analysis of the pdx-1 (snz-1/sno-1) Region of the Neurospora crassa Genome: Correlation of Pyridoxine-Requiring Phenotypes With Mutations in Two Structural Genes

Laura E. Bean, William H. Dvorachek, Jr., Edward L. Braun, Allison Errett, Gregory S. Saenz, Mara D. Giles, Margaret Werner-Washburne, Mary Anne Nelson, and Donald O. Natvig*

Department of Biology, University of New Mexico, Albuquerque, NM 87131 (all authors); and National Center for Genome Resources, Santa Fe, New Mexico 87505  (E.L.B.)
E.L.B. is currently in the Department of Zoology at the University of Florida.

We report the analysis of a 36-kbp region of the Neurospora crassa genome, which contains homologs of two closely linked stationary phase genes, SNZ1 and SNO1, from Saccharomyces cerevisiae. Homologs of SNZ1 encode extremely highly conserved proteins that have beenimplicated in pyridoxine (vitamin B6) metabolism in the filamentous fungi Cercospora nicotianae and in Aspergillus nidulans. In N. crassa, SNZ and SNO homologs map to the region occupied by pdx-1 (pyridoxine requiring), a gene that has been known for several decades, but which was not sequenced previously. In this study, pyridoxine-requiring mutants of N. crassa were found to possess mutations that disrupt conserved regions in either the SNZ or SNO homolog. Previously, nearly all of these mutants were classified as pdx-1. However, one mutant with a disrupted SNO homolog was at one time designated pdx-2. It now appears appropriate to reserve the pdx-1 designation for the N. crassa SNZ homolog and pdx-2 for the SNO homolog. We further report annotation of the entire 36,030-bp region, which contains at least 12 proteincoding genes, supporting a previous conclusion of high gene densities (12,000–13,000 total genes) for N. crassa. Among genes in this region other than SNZ and SNO homologs, there was no evidence of shared function. Four of the genes in this region appear to have been lost from the S. cerevisiae lineage.


This work was supported by National Science Foundation grants HRD-9550649 (D.O.N., M.A.N., M.W.-W., and Robert K. Miller), MCB-9603902 (D.O.N.), IBN-9870878 (M.W.-W.) and MCB-9874488 (M.A.N.). A.E. and M.G. were supported in part by the Minority Biomedical Research Support program of the University of New Mexico (National Institutes of Health grant GM-52576). E.L.B. was supported in part by United States Department of Agriculture fellowship 1999-01582. G.S.S. was supported in part by a postdoctoral fellowship from the Ford Foundation.

* Corresponding author