Genetics, Vol. 157, pp. 1067-1075
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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 been
implicated 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 protein
coding 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.