A wild type strain of
Neurospora crassa produced aerial hyphae and luxuriant conidia in standing culture in low phosphate liquid media.
nuc-1 and
nuc-2, which have no ability to derepress repressible cyclic phosphodiesterase (cPDase) (3′; 5′-cyclic AMP 5′-nucleotidohydrolase,
EC 3.1.4.17) and several other repressible enzymes, did not form them. Heterocaryon between them restored the abilities not
only to produce aerial hyphae and conidia but also to produce cPDase. Revertants from
nuc-1 and a mutant in alkaline phosphatase,
pho-2, produced aerial hyphae and conidia in low phosphate condition, whereas a mutant in cPDase,
pho-3, produced only a limited amount of them.
In media containing low levels of 2′, 3′-cAMP, the wild type, the revertants from
nuc-1, pho-2 and
pho-3 produced aerial hyphae and conidia in abundance, whereas in media containing 3′, 5′-cAMP these strains produced no or only
limited amounts of them. In low phosphate media
nuc-1, nuc-2 and
pho-3 showed higher levels of 3′, 5′-cAMP as compared with those strains which have the ability to derepress cPDase. The cPDase
activities in crude mycelial extracts from
nuc-1 and
pho-3 grown in low phosphate media were 5.6 and 17.5% of that of
pho-2 when assayed for 3′,5′-cAMP at an intracellular level of 2 μM.
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