title: Aspergillus nidulans hypB encodes a Sec7-domain protein important for hyphal morphogenesis.
abstract: Aspergillus nidulans strains containing the hypB5 temperature sensitive allele have a restrictive phenotype of wide, highly-branched hyphae. The hypB locus was cloned by phenotype complementation using a genomic plasmid library. hypB5 is predicted gene AN6709 in the A. nidulans genome database, which encodes a putative Sec7 domain protein, likely to act early in COPI-mediated vesicle formation for retrograde Golgi to ER transport. The A. nidulans hypB5 allele has a single mutation, cytosine to guanine predicted to cause a nonconservative amino acid change, alanine to proline, in a conserved helix adjacent to the Sec7p nucleotide binding site. This would likely reduce the stability of a highly conserved loop important for nucleotide binding, and is consistent with temperature sensitivity of hypB5 strains. Deletion of AN6709 showed that hypB(Sec7) was not essential. AN6709Delta hyphae resembled the hypB5 restrictive phenotype. As has been shown previously for hypA1 mutants, shifting established hypB5 mutant hyphae from a growth temperature of 28-42 degrees C caused septation in and death of tip cells and growth activation of basal cells.
authors.affiliation: Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Sask., Canada S7N 5E2.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.forename: Amira M
authors.initials: AM
authors.lastname: El-Ganiny
authors.forename: Geoffrey E
authors.initials: GE
authors.lastname: Bray
authors.forename: David A R
authors.initials: DA
authors.lastname: Sanders
authors.forename: Susan G W
authors.initials: SG
authors.lastname: Kaminskyj
mesh_terms: D019943:Amino Acid Substitution / Q000235:genetics; D001233:Aspergillus nidulans / Q000166:cytology / Q000235:genetics / Q000502:physiology*; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000502:physiology*; D017353:Gene Deletion; D005816:Genetic Complementation Test; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000502:physiology*; D006358:Hot Temperature; D025301:Hyphae / Q000166:cytology / Q000254:growth & development; D008958:Models, Molecular; D020125:Mutation, Missense
chemical_list: D005656:Fungal Proteins; D020662:Guanine Nucleotide Exchange Factors; C066755:Sec7 guanine nucleotide exchange factors