11 alpha-hydroxylation of progesterone in the eucaryotic filamentous fungus Rhizopus nigricans is catalyzed by a monooxygenase. Three components of this multienzyme system, cytochrome P-450, ...rhizoporedoxin and a FAD containing rhizoporedoxin reductase have been separated from the postmitochondrial fraction on DEAE cellulose. Using NADPH as electron donor we showed that the presence of all three components was necessary for the reconstitution of the active electron transport chain.
3, 3', 4, 5'-Tetrahydroxystilbene (1) isolated from the heartwood of Cassia garrettiana CRAIB. showed a broad spectrum of physiological activities, including antifungal, phytogrowthinhibitory and ...ichthyotoxic activities. Firstly. 1 showed antifungal activity ; the minimal growthinhibitory concentration (MIC) was 25 μg/ml against Penicillium citrinum and Rhizopus nigricans. Secondly, 1 showed rather strong inhibitory activity on the growth of five plant species at a concentration of 500ppm. Thirdly. 1 had ichthyotoxic activity. The median tolerance limit (TLm) at 48h was 26.5ppm in Oryzias latipes TEMMINCK et SCHLEGEL and 31.5 ppm in Carassius auratus LINNE. Studies were made on the activities of derivatives of 1, i.e., 3, 3', 4, 5'-tetrahydroxystilbenetetraacetate (2), 3, 3', 4, 5'-tetrahydroxystilbene-tetramethyl ether (3), and 3, 3', 4, 5'-tetrahydroxybibenzyl (4). The activities of these derivatives, however, were lower than those of 1, except for the phytogrowth-inhibitory and ichthyotoxic activities of 4. It is clear that for antifungal activity, both the hydroxyl groups attached to the benzene rings and the trans-olefin structure are necessary, while for the phytogrowth-inhibitory and ichthyotoxic activities, only the hydroxyl groups attached to the benzene rings are necessary.
The colony interaction and hyphal interference between F. oxysporum f. sp. lycopersici and R. nigricans were studied. Intermingling growth of both colonies was observed. Hyphal parasitism was ...characterized by coiling, penetration, ramification inside host, rupture of host hyphae and frequent chlamydospore formation. The host hyphae bulged out and deposited a 'wall like barrier'. The parasite penetrated the barrier and developed further.
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