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Morphogenesis of carotene-containing male gametangia of the gametophytic generation of Allomyces macrogynus and A. arbusculus is selectively disturbed by heavy, subtoxic doses of diphenylamine (1/60,000 DPA) which fully inhibit carotenogenesis. DPA-effects on growth, carotenogenesis, and conidial differentiation have been studied in Neurospora crassa. The rate of growth on Fries agar medium (measured in growth tubes) is reduced ⅓ with DPA 1/80,000 and ¾ with DPA 1/40,000. In Fries liquid medium, growth is less or not affected by similar doses of DPA. In these conditions, 1/40,000 DPA strongly inhibits biosynthesis of carotenoids but requires the additional presence of Fe+2 for effective activity al the concentration 1/80,000. Conidial differentiation, normally accompanied by a prominent increase of the acidic carotenoids and the spirilloxanthin, is suppressed by 1/40,000 DPA or 1/80,000 DPA + Fe which have an especially strong inhibitory effect on these "conidial oxycarotenoids". A marked accumulation of phytoene has been defected in such sterile mycelia of Neurospora. Residual DPA bas not been detected with the nitric acid coloration test in the phytoene fraction of wild type extracts. Moreover, phytoene and DPA are absent in the insaponifiable extract of au albino mutant of Neurospora crassa also grown on a DPA medium. These facts and the relation DPA-Fe point lo a bio-oxidative destruction of DPA which might well act as an antioxidant progressively destroyed in preventing the oxidation of the precursors of the caroteuoids. [ABSTRACT FROM AUTHOR]

The gametes of Allomyces javanicus exhibit a nuclear cap essentially made of ribonucleoprotein with sulphydryl groups. When dipped in phosphate buffered solutions of boric acid M/20-M/400, the male and female gametangia of Allomyces liberate giant male and female gametes. Such giant gametes exhibit either a single regular nuclear cap (with 2 or 3 nuclei) or a massive and irregular basophilic formation (with 4-10 nuclei). Boric acid may interfere with ribonucleic acid, essential constituent of the nuclear cap, during the cleavage of the gamete-units in the gametangia. [ABSTRACT FROM AUTHOR]