System analysis of Phycomyces light-growth response: double mutants

Area of Science:

• Mycology
• Molecular Biology
• Genetics

Background:

• The light-growth response and phototropism in Phycomyces are crucial behaviors.
• Seven genes (madA-madG) are known to regulate these responses.
• Previous studies analyzed wild-type and single mutants.

Purpose of the Study:

• To investigate dynamic interactions among mad gene products.
• To characterize the light-growth response in double mutants.
• To elucidate the structure of the sensory transduction pathway.

Main Methods:

• Studied 21 pairwise double mutants of Phycomyces using Gaussian white-noise stimuli.
• Analyzed input-output relations via Wiener kernels and transfer functions.
• Compared double-mutant data with single mutants and wild-type.

Main Results:

• Identified specific double mutants (e.g., AB, BC) with weak but detectable responses.
• Rejected dynamic independence for multiple gene combinations (e.g., AD, AE, AG, BC, BD, BE, BF, BG, CD, CE, CF, DE, DG, EF) at a 5% significance level.
• Developed a pictorial scheme illustrating dynamic interactions among mad gene products.

Conclusions:

• Significant dynamic interactions exist among mad gene products.
• High interaction between 'input' (A, B, C) and 'output' (D, E, F, G) genes.
• Suggests the sensory transduction pathway is a multimolecular complex.