Physiological Changes during Protoperithecial Differentiation in Neurospora tetrasperma

Abstract

Protoperithecial differentiation in Neurospora tetrasperma proceeds in four clearly discernible stages: ascogonial bud, ascogonial hook, ascogonial coil, and protoperithecium. This morphogenetic sequence was completely but transitorily blocked at 37°C. Under low oxygen tensions or in the absence of carbon dioxide, only ascogonial coils were differentiated. Glycolytic inhibitors such as 2-deoxy-D-glucose interfered with the ascogonial differentiation. Citric acid cycle inhibitors such as fiuoroacetate selectively blocked the further development of ascogonial coils into protoperithecia. Differentiating cultures at 25'^C responded positively to external sucrose with respiratory quotients above 1.0, whereas non-differentiating cultures at 37°C, although respiring at high rates, never reached RQ 1.0. These results indicate that carbohydrate metabolism via fermentative glycolysis functions normally in ascogonia differentiating (25 C) cultures only.Comparative chemical analysis showed delayed RNA synthesis, sharp disturbances in protein biosynthesis and metabolism, and lower levels of carbohydrate and bound lipids in young cultures at 37"C.Polyols, especially ribitol and xylitol utilized as sole source of carbon, induced abundant protoperithecial morphogenesis at 37'C. This alleviating effect of polyols was negated by the addition of sugars at 37°C and shown to be a specific metabolic effect.

Neurospora from Natural Populations: A Global Study

“…Differences in conditions required for crossing in the laboratory may reflect the habitats in which crossing occurs in nature. In N. tetrasperma, the sexual cycle is not inhibited by levels of ammonium nitrogen or by elevated temperatures that would block crossing of N. crassa or other heterothallic species (Viswanath-Reddy and Turian, 1975, and our unpublished observations). Strains of N. discreta and N. sitophila that cross well on filter paper but not when sucrose or glucose is provided as the carbon source are known Fairfield and Turner, 1993).…”

Importance of MAP Kinases during Protoperithecial Morphogenesis in Neurospora crassa

“…hyphal lassoes). The formation of hyphal lassoes has been described by several authors, and interpreted to be abortive ascogonial coils or ‘pseudo-ascogonia’ in N. crassa [81] , [82] , N. tetrasperma [83] and S. macrospora [84] . However, we are not aware of any evidence to support this interpretation in N. crassa as has been recently discussed for hyphal lassoes in Aspergillus nidulans [85] .…”

Multi-targeted priming for genome-wide gene expression assays

“…Thus, these pathways are tightly controlled upon nutrient limitation. Decreasing levels of protein, RNA and soluble aminonitrogen were observed during protoperithecia development as early as 1975 [ 47 ]. Additionally, ribosomes are rapidly degraded by autophagy upon nutrient starvation in S. cerevisiae , implying that degradation of excessive ribosomes may help to shut down protein translation rapidly and provide an important source of new building blocks to maintain cellular homeostasis [ 48 ].…”