Characterization ofcpd-1 andcpd-2 mutants which affect the activity of orthophosphate regulated cyclic phosphodiesterase inNeurospora

Summary Enzymatic and genetic characterization ofcpd-1 andcpd-2, which exhibit rhythmic conidiation in liquid media and on solid media, were described with band (bd) strain as a reference.Cpd-1 andcpd-2 showed reduced growth in orthophosphate-free cyclic 3,5-AMP media, whilebd showed wild-type level of growth in the media. In low-phosphate media,cpd-1 andcpd-2 produced 19.2% and 9.8% of orthophosphate-regulated cyclic phosphodiesterase (cPDase) in culture media, while bd produced 123%. The intracellular levels of cPDase with K_m of 1 × 10^–5 M in high-phosphate media incpd-1, cpd-2 and bd were about 20%, 15%, and 10% of that in wild-type, respectively. In low-phosphate media, roughly equal levels of cPDase with K_m of 1 × 10^–5 M were produced in all strains, whereas the production of cPDase with K_m of 2 × 10^–3 M was reduced incpd-2, and that of cPDase with K_m of 1 × 10^–2 was reduced incpd-1 andcpd-2. The levels of intracellular cyclic 3,5-AMP incpd-1, cpd-2, andbd in high-phosphate media were 13.1%, 10.1%, and 69.6% of that in wild-type. Adenylate cyclase activity incpd-1, cpd-2, bd, andcr-1 was 69.3%, 34.0%, 63.2%, and 20.3% of that of wild-type (74A). The levels of Mg⁺⁺-stimulated cyclic phosphodiesterase incpd-1, cpd-2, bd, andcr-1 at 0.2M cyclic 3,5-AMP were 199%, 137%, 329%, and 293% of that of wild-type. It was suggested thatcpd-1, cpd-2, andbd are the genes controlling the levels of enzymes for cyclic 3,5-AMP.Cpd-I was mapped on LG IVR 19.4% distal topyr-2 andcpd-2 was mapped on LG IL 5.6% proximal toarg-1.