Circadian Nature of a Rhythm Expressed by an Invertaseless Strain of Neurospora crassa

Abstract

Summtary. A new strain of Neuirospora crassa which exhibits a rhythm of conidiation when growing along an agar surface in a growth ttube is described. The rhythm has been shown to be circadian for it meets the following criteria: A) the period under constant environmental conditions in the dark is abolut 24 hours (22.7 hours at 250) ; B) the period is relativcly temperatuire-independent (Q, We have developed a system for the biochemical stuldy of a circadian rhythm employing a new strain of Neurospora crassa (timex)2 which satisfies both criteria mentioned above. Pittendrigh et al. (16) were the first to point ouit the advantages of working with Neutrospora, and Sussman, Dturkee, and Lowry (21), Berliner and Neuirath (4), and Bianchi (5) have uised Neuirospora to stuidy the rhythm expressed in the clock strains described by Sussman, Lowry, and Duirkee (11,22

Effects of Temperature Perturbations on Circadian Conidiation in Neurospora

“…Although the effects of steady-state temperature on the period of the circadian rhythm of conidiation in Neurospora crassa have previously been established (21,24), the effects of temperature perturbations on this system have not been studied. Such an investigation is desirable in view of the increasing evidence (27) that membranes are components of circadian oscillators, and the speculation that temperature-induced alterations of membrane lipid composition may be related to temperature conpensation of biological rhythms (16).…”

“…The effects of temperature steps (up and down), pulses (up and down), and cycles on circadian conidiation in Neurospora were measured, as well as the effects of long term low tempera- (24). Conidia were inoculated onto 8 ml of glucose-arginine medium in 55-cm Pyrex growth tubes.…”

“…Brief illumination was provided by ruby-red safelights (GE BBX, 40-w) which have no effect on the bd conidiation rhythm (24). Temperature perturbations were conducted in either a growth chamber (Percival I-30L; ± 0.3 C) or an incubator (LabLine/CS&E model 600; ± 0.5 C) housed in the darkroom.…”

“…In experiments requiring light, the growth tubes were incubated in the growth chamber (I-30L) described above. Two 24.0 h; the band center defined as 2200 CT).…”

“…Since there are major changes in the growth rate and minor changes in period at different temperatures (24), appropriate corrections were made when analyzing the experimental tubes. The greatest variability occurred near the breakpoints in the phase response curves where both the average phase shifts and the CT positions ofthe breakpoint were within 3 h ofeach other in similar experiments.…”