System analysis of Phycomyces light-growth response: single mutants

Area of Science:

• * Plant biology
• * Biophysics
• * System identification

Background:

• * Phototropism in Phycomyces is a complex light-mediated growth response.
• * Previous work established an analytical model for light-growth response kinetics.

Purpose of the Study:

• * To investigate the phototropic light-growth response in seven Phycomyces mutants (madA-madG) using system identification.
• * To characterize the input-output relationship (Wiener kernels) of these mutants and wild-type strains under varying light intensities.

Main Methods:

• * Application of the white-noise method for system identification.
• * Evaluation of Wiener kernels representing the light-growth response.
• * Analysis of transfer functions and fitting to an analytical model.

Main Results:

• * Mutant madA exhibited a response approximately twice as strong as wild-type at high light intensity (10 W m-2).
• * Most mutants (except madA) showed smaller first-order kernels than wild-type.
• * Specific mutants displayed altered kernel kinetics: prolonged time course (madB, madC), longer latency (madB), shallow/extended negative phase (madE, madF, madG), and shorter latency/time course (madD).
• * Kernel features correlated with parameters from the analytical model.
• * The madC mutant's kernel was better described by a model with fewer low-pass filters.

Conclusions:

• * Different mad genes (madA-madG) play distinct roles in regulating the transient light-growth response in Phycomyces.
• * The white-noise method effectively differentiates kinetic responses of phototropism mutants.
• * The findings provide insights into the molecular mechanisms underlying phototropism in Phycomyces.