Filtering Effect For Light Entrainment Of Neurospora System

Circadian clock is used to predict the time change and adjust the physiological an inner mechanism of the steady state, is an important basic characteristic of organisms. Because of the biological clock being formed in the periodical change of day and night during the earth’s rotation environment, light is the important factor that affects circadian rhythms. Based on the pulse spore fungus as an example to study the effect of light on this clock, we draw issues to discuss from the light entrainment of neurospora system and explore filtering effect.Found in the biological experiment of neurospora(Experimental results has not yet been published by Professor Jinhu Guo in zhongshan university), when entraining the neurospora with longer photoperiod, the rhythm of the neurospora changes along with the rhythm of light, but when using shorter photoperiod(frequent light cycle) to entrain the neurospora, the rhythm of the neurospora will not be affected by the traction of light, which will return to the cycle of self-oscillation for 22.03 hours.For the above phenomenon, this article mainly studied three core issues:First, we establish the ordinary differential equation of mathematical model of neurospora system, through the computer simulation and calculation, and combined with the mathematical method of the fast Fourier transform, we also discovered the phenomenon of double competition rhythm.Second, further simplifying the model of neurospora system, and extracting two motifs to proceed theory analysis. We explored the filter effect of the parameters in a single motif and several motifs which were connected in series, respectively.Third, in the actual neurospora system, through the analysis of the filter method, we found the filtering effect of the main parameters in their own rhythm system through computer simulation. Then we observed the filter changes by using the method of direct perturbing parameters, at last we compared the consistency of the results with the research methods of filtering analysis. In this paper, we have several results and contributions:First, 1)Using mathematical method of fast Fourier transform and writing time- 2 FFT algorithm, through computer programming and drawing the FFT spectrum diagram, we discovered two frequencies of rhythm in the light entrainment of neurospora system, we found that as the light traction cycle being longer, light drew amplitude increasely, its oscillation amplitude decreased until it disappeared.These two rhythms, presented a trend of competing. 2) when traction neurospora system with frequent light, light amplitude increased with the own amplitude declined. One important reason, the filtering effect of system were at work, but the real reason is the increasing stimulation intensity of light, which led to a decline in its amplitude.Second, we simplified the complex system with a negative feedback nonlinear and extracted two motifs. Using laplace transform mathematical methods to calculate the transfer function of each motif, we studied the amplitude-frequency characteristic on signal communication. Not only did we discover the filtering effect of various parameters in a single motif, but also found that new filtering effect of the parameters of the motif in series. Finally, after the superposition of two motifs in series were studied, we compared thefiltering effect of a single motif and found that as the number of rings increasing, system let less and less high frequency signal pass, instead, it let more low frequency signal pass, which showed stronger high frequency filtering effect.Third, the filtering analysis theory is used for the actual neurospora system, we found that when frq m RNA transcription rate increased, the protein phosphorylation FRQ rate decreased and the rate of protein Hypo_FRQ going into cell nuclear reduced, filter effect of the system would be reduced. At the same time, by the parameter perturbation method,we observed the filter effect of each parameter is consistent with the filtering method which were studied by the filtering method, so we considered the method of using transfer function to study the filtering effect in the neurospora system is feasible.