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
Le. Bean et al., 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, 157(3), 2001, pp. 1067-1075
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 Asperg
illus nidulans. In N. crassa, SNZ and SNO homologs map to the region occupi
ed 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 SATO homolog. Previously, nearly al
l of these mutants were classified as pdx-1. However, one mutant with a dis
rupted SNO homolog was at one time designated pdx-2. It now appears appropr
iate 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-b
p region, which contains at least 12 protein coding genes, supporting a pre
vious 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 w
as no evidence of shared function. Four of the genes in this region appear
to have been lost from the S. cerevisiae lineage.