[Selection and characterization of Penicillium cyclopium mutants with altered developmental program]

Nuclear inheritance of the biosynthesis of cyclopenin and cyclopenol in Penicillium cyclopium

Balanced heterokarions were grown from Penicillium cyclopium aux-glu 1, a glutamic acid auxotroph producing benzodiazepine alkaloids of the cyclopenin-cyclopenol group, and P. viridicatum aux-met 1, a methionine auxotroph forming these alkaloids in traces only. In contrast to the hyphae of the parent strains, the hyphae of the heterokarions were dark orange-brown and grew well on media without the auxotrophic factors. In surface cultures they synthesized the benzodiazepine alkaloids cyclopenin and cyclopenol in amounts similar to those formed by the hyphae of P. cyclopium aux-glu 1. From the monokariotic conidiospores of the heterokarions homokariotic daughter strains were obtained which were similar to the parent strains in every respect. Hence no exchange of features of cyclopenin-cyclopenol biosynthesis took place between the parent strains at the stage of the heterokarion. This result indicates that the formation of cyclopenin and cyclopenol in P. cyclopium aux-glu 1 and the nearly complete lack of biosynthesis of these compounds in P. viridicatum aux-met 1 is encoded within the nucleus and is not influenced by plasmic genetic material.

Phenol oxidase activity and pigment synthesis in conidiospores of Penicillium cyclopium

Phenol oxidase (PO) of Penicillium cyclopium belongs to the laccases (E.C. 1.14.18.1). By PAA-gel electrophoresis three forms of the enzyme were detected. Most of the PO in emerged sporulating cultures accumulates in the cell wall of the conidiospores. However, a high percentage is not bound to the wall constituents and can be easily removed with aqueous solutions. This soluble fraction was 570-fold enriched by (NH4)2SO4-precipitation, followed by chromatography on sephadex G 200 and on hydroxylapatite-cellulose, The necessity of PO for conidiospore pigmentation was shown by means of suspended spores whose rates of pigment accumulation resemble those of conidia maturing in situ. Pigmentation is stopped if PO is inhibited by diethyldithiocarbamate. This corresponds to the fact that in strains with heavily pigmented conidiospores PO activity is much higher than in strains with weakly pigmented or unpigmented spores. Also the time course of PO accumulation in the latter strains is different from that of the former. Furthermore, in mutant res-eth 1 which has unpigmented conidiospores, PO isoenzyme no. 3 could not be detected.