Tip Growth of Neurospora crassa under Glucose Deprivation

摘要

Growth parameters of vegetative hyphae and isolated tip fragments of the mycelial fungus N. crassawere studied after complete substitution of an easily metabolized carbon source (glucose) for a non-metabo-lized one (sorbitol). The images of growing tips were recorded at 20-30-min intervals. Using original imageprocessing software, geometrical parameters of the hyphal trees (length and number of branches, area of convexpolygons circumscribed about the hyphal trees, etc.) were determined and growth characteristics, such as rateof tip elongation (V) and the ratio of the total hyphal length to the number of growing tips (termed "hyphalgrowth unit", HGU), were calculated. It is shown that after 4-5-h growth in sorbitol-enriched media growthcharacteristics of intact hyphae did not differ significantly from the corresponding parameters of hyphae grow-ing in glucose-enriched media. In isolated tip fragments (about 800-gm long), the values of V were lower thanthose in intact hyphae but did not depend on the carbon source in the nutrient media. However, in such frag-ments growing in sorbitol-enriched media the number of branches decreased, while the HGU value and thenumber of large intracellular vacuoles increased. Staining of cells with a standard chitin probe, CalcofluorWhite (10μg/m1), did not reveal any considerable differences in hyphal cell walls and septa in tip fragmentsgrown in the presence of different carbon sources. Possible mechanisms of the dependence of the tip growthparameters on the glucose deficiency are discussed.