title: The PHOA and PHOB cyclin-dependent kinases perform an essential function in Aspergillus nidulans.
abstract: Unlike Pho85 of Saccharomyces cerevisiae, the highly related PHOA cyclin-dependent kinase (CDK) of Aspergillus nidulans plays no role in regulation of enzymes involved in phosphorous acquisition but instead modulates differentiation in response to environmental conditions, including limited phosphorous. Like PHO85, Aspergillus phoA is a nonessential gene. However, we find that expression of dominant-negative PHOA inhibits growth, suggesting it may have an essential but redundant function. Supporting this we have identified another cyclin-dependent kinase, PHOB, which is 77% identical to PHOA. Deletion of phoB causes no phenotype, even under phosphorous-limited growth conditions. To investigate the function of phoA/phoB, double mutants were selected from a cross of strains containing null alleles and by generating a temperature-sensitive allele of phoA in a deltaphoB background. Double-deleted ascospores were able to germinate but had a limited capacity for nuclear division, suggesting a cell cycle defect. Longer germination revealed morphological defects. The temperature-sensitive phoA allele caused both nuclear division and polarity defects at restrictive temperature, which could be complemented by expression of mammalian CDK5. Therefore, an essential function exists in A. nidulans for the Pho85-like kinase pair PHOA and PHOB, which may involve cell cycle control and morphogenesis.
authors.affiliation: Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Xiaowei
authors.initials: X
authors.lastname: Dou
authors.forename: Dongliang
authors.initials: D
authors.lastname: Wu
authors.forename: Weiling
authors.initials: W
authors.lastname: An
authors.forename: Jonathan
authors.initials: J
authors.lastname: Davies
authors.forename: Shahr B
authors.initials: SB
authors.lastname: Hashmi
authors.forename: Leena
authors.initials: L
authors.lastname: Ukil
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Osmani
mesh_terms: D000595:Amino Acid Sequence; D001233:Aspergillus nidulans / Q000201:enzymology*; D001483:Base Sequence; D018844:Cyclin-Dependent Kinases / Q000737:chemistry / Q000378:metabolism*; D017931:DNA Primers; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D018844:Cyclin-Dependent Kinases