Effects of the Self-Inhibitor of Dictyostelium discoideum on Spore Metabolism

Abstract

The effects of the self-inhibitor, N,N-dimethylguanosine, on the metabolism of spores of Dictyostelium discoideum were investigated. It is concluded that since both self-inhibited and activated spores had similar initial Qo, values, the site of action of the self-inhibitor was not on respiratory metabolism. Incorporation of [U14C]glucose revealed that organic acids and amino acids accumulated in self-inhibited spores and that protein synthesis was inhibited. Succinic acid accumulated only when the activated self-inhibited spores became anaerobic so its accumulation was not directly related to self-inhibition. Phenylalanine, methionine and tryptophan were absent in dormant spores but appeared after heatactivation and accumulated in self-inhibited spores. The accumulation of amino acids was related to the inability of self-inhibited spores to synthesize protein.In viva analysis showed that protein synthesis began early in spore germination and that the self-inhibitor immediately arrested this process when added to activated spores and slowed it when added to germinating spores. No effect of self-inhibitor on RNA synthesis during germination was detected. Thus, we conclude that the self-inhibitor, a methylated base of guanine, regulated spore germination by preventing the synthesis of protein necessary for subsequent development.

Germination of Penicillium paneum Conidia Is Regulated by 1-Octen-3-ol, a Volatile Self-Inhibitor

“…From the mucilage that surrounds the conidia of this fungus, a self-inhibitor of germination named mycosporine-alanine has been identified and characterized (26). Germination is also retarded in pustules of rust fungi (Basidiomycetes) where cisferulic acid methyl ester and cis-3,4-dimethoxycinnamic acid methyl ester have been identified (28, 36).Self-inhibitors have been characterized in Puccinia, Uromyces, Colletotrichum, Dictyostelium, Fusarium oxysporum, and Aspergillus and can be volatile or nonvolatile (2,3,16,24,28).They also can influence other fungal processes, for example, mycosporine-alanine produced by Colletotrichum graminicola prevents appressorium formation (25, 26). The self-inhibitors produced by Glomerella cingulata and Dictyostelium discoideum inhibit protein synthesis (2, 27).…”

“…Self-inhibitors have been characterized in Puccinia, Uromyces, Colletotrichum, Dictyostelium, Fusarium oxysporum, and Aspergillus and can be volatile or nonvolatile (2,3,16,24,28).…”

“…The self-inhibitors produced by Glomerella cingulata and Dictyostelium discoideum inhibit protein synthesis (2,27).…”

Tetrahydropteridines possess antioxidant roles to guard against glucose-induced oxidative stress in Dictyostelium discoideum

“…2C). Because phase-dark spores are known to originate from mitochondria with disrupted cristae (11), it seemed that irreversibly damaged mitochondria deteriorated the viability of spores, which were known to depend more on aerobic respiration (12). Taken together, the results strongly support the glucose-dependent increase of oxidative stress and mitochondrial dysfunction in Dictyostelium cells, thereby suggesting that glucose-induced oxidative stress may be responsible for the poor cell growth observed at the high glucose concentration (2X).…”

RNA and protein synthetic patterns during germination of Polysphondylium pallidum microcysts

“…Actinomycin D prevents the incorporation of [3H]uridine into acid-precipitable material; yet, as shown, it has no effect on germination (O'Day et (11. 1976 The mechanisms controlling germination in microcysts of Polysphondylirl~n seem to differ from those in spores of Dictyostelium, where some RN A synthesis is required for germination (Bacon and Sussman 1973;Yagura and Iwabuchi 1976). However, precursor incorporation data similar to those in P. pallidrlm microcysts have been reported for several fungal spores, suggesting that similar control mechanisms exist in these other systems (Brambl and Van Etten 1970;Olson and Fuller 1971;Rousseau and Halvorson 1973).…”