The regulation of sclerotium initiation in Sclerotium rolfsii by glucose and cyclic AMP

Abstract

Sclerotium rolfsii, grown in a shaken submerged culture, developed a potential for the formation of sclerotia. This potential was inhibited by the presence of glucose in the culture medium. The cultures were capable of producing sclerotia, after transfer to stationary incubation, when glucose was exhausted and the biomass reached its maximal level. The level of adenosine 3′,5′-cyclic monophosphate (cAMP) sharply increased upon glucose depletion and decreased upon glucose addition. Sclerotium rolfsii was grown in a chemostat with glucose of limiting concentration at a dilution rate of 0.05/h. Samples from the chemostat possessed the potential to produce initials when poured into empty Petri plates. Addition of glucose to these plates changed the fungal growth pattern from further differentiation to vegetative growth. Glucose supplementation to clearly differentiated initials did not inhibit further development. It was observed that during morphogenetic events endogenous substrates, e.g., cell wall components, were utilized.

In vitro initiation of sclerotia ofSclerotium cepivorum

“…Similarly, the triggering of sclerotium formation by a nutritional barrier, i.e, growing from a rich medium to a poor medium, is Downloaded by [University of Toronto Libraries] at 11:20 07 December 2014 likely due to a nonspecific restriction of growth and is similar to the results reported for S. cepivorum by Christias and Lockwood (1973). This result is also consistent with the results of Christias and Lockwood (1973), Hadar et al (1983), and Punja (1986) for S. rolfsii.…”

“…When the growth rate was slowed by restricting the carbon source in the medium, sclerotium production was reduced. Hadar et al (1983) also found that depletion of glucose in the medium restricted mycelial growth of S. rolfsii and induced the formation of sclerotia.…”

Regulation of Glycogen Synthase in Sclerotium rolfsii

“…rolfii develops the potential for sclerotium formation only when glucose is exhausted in the growth medium (Hadar et al, 1983). Since the activity of glycogen synthase a was more sensitive to environmental change than the total glycogen synthase activity, we followed the former activity during exposure of the mycelium to starvation conditions.…”

“…rolfsii, which are probably related to cAMP levels (Hadar et al, 1983). Watkinson (1979) suggested that in the early stages of all types of vegetative aggregations morphogenesis takes place at the expense of endogenous substrates.…”

“…cannot produce sclerotia, but it develops a potential for sclerotium formation as a response to glucose depletion in liquid medium (Hadar et al, 1981). Concomitantly, the intracellular level of cAMP sharply increases upon glucose removal (Hadar et al, 1983). In many biological systems cAMP plays a role in stimulating the catabolism of stored carbon reserves such as glycogen and triglycerides (Pall, 1981).…”