Morphology and Genetics of a Periodic Colonial Mutant of Neurospora Crassa

Abstract

A mutant of strain 69–1113a of Neurospora crassa, which shows periodic growth upon both complete and minimal media, was named “clock,” and some of the morphological and genetic differences between this mutant and the “patch” and “wild” strains were investigated. In contrast to the uniform growth of “wild,” the “clock” mutant produces a series of bands formed by cymelike aggregations of hyphae which become progressively more dense and finally mark the end (front) of a growth band. A new growth band is formed by a number of hyphae which grow out as in “wild” strains and dichotomize and form new cymes which again become progressively more dense and finally form a new front. It is shown that “clock” continues its rhythmic growth when cultured in continuous darkness. Some “wild” strains were induced to grow periodically on appropriate media. A medium containing equal quantities of sorbose and sucrose caused strain 65–811A (a “wild”) to produce the “patch” type growth. Random isolation, as well as ordered isolation, of ascospores following a cross between “wild” and “clock” show a 1: 1 segregation indicating that “clock” differs from “wild” by a single gene.

Effects of cytochalasins onNeurospora crassa

“…Given effects on branching such as those seen in Fig. 2, it is interesting to note that there is a strong resemblance between the fan-like assemblage of branches in cytochalasin-treated cultures and those reported by SussMAN et al [22] depicting the normal pattern of growth of the clock mutant of Neurospora.…”

Ultradian Rhythms in the Transcriptome of Neurospora crassa

“…Another open question is whether the harmonics are generated by an independent clock or an oscillator. There is a rich history of non-circadian oscillations in Neurospora , such as the FRQ-less oscillator (FLO) ( Sussman et al., 1964 ), nitrate reductase oscillator (NRO) ( Christensen et al., 2004 ), and choline deficiency oscillator (CLO) ( Lakin-Thomas, 1998 ), that can show periods between 10 and 100 hr depending on metabolic and temperature conditions. Importantly, these non-circadian rhythms have not been observed simultaneously with an intact circadian oscillator as is the case here.…”

Making Time: Conservation of Biological Clocks from Fungi to Animals

“…There is even a rhythm in the formation of nematode traps by the nematophagous fungus Arthrobotrys oligospora (112). The first noncircadian rhythms in Neurospora crassa date from the 1960s (113), and more than three decades ago, the defining FLO rhythm was described in the frq-null strain frq 9 (114,115). When frq was cloned and the mutant alleles analyzed the allele was shown to encode a truncated and nonfunctional FRQ and the existence of the noncircadian oscillator was confirmed (68); it can have a period between 12 and 34 hours depending on the nutrition and temperature (that is, it is completely uncompensated) and cannot be entrained by light.…”