Palit A, Lipson E D
Department of Physics, Syracuse University, NY 13244-1130.
Biol Cybern. 1989;60(5):385-93. doi: 10.1007/BF00204776.
The sum-of-sinusoids method of nonlinear system identification has been applied to the light-growth response of the Phycomyces sporangiophore. Experiments were performed on the Phycomyces tracking machine with the wild-type strain with single and double mutants affected in genes madA, madB, and madC. The sum-of-sinusoids test stimuli were applied to the logarithm of the light intensity. The log-mean intensity level was 10(-1) W m-2 and the wavelength was 477 nm. The system identification results are in the form of first- and second-order frequency kernels, which are related to temporal kernels that appear in the Wiener functional series. The first-order kernels agree well with those obtained previously by the white noise method. In particular, the madA madB and madB madC double mutants show very weak responses. With the superior precision of the sum-of-sinusoids methods, we have achieved sufficient resolution to measure and analyze their second-order kernels. The first- and second-order frequency kernels were interpreted by system analysis methods involving a nonlinear parametric model. In addition a nonparametric hypothesis concerning interactions of gene products was tested. Results from the interaction tests confirm the earlier conclusion that the madB and madC gene products interact. In addition, with the enhanced precision and with the extension to nonlinear analysis, we have found evidence of interaction of the madA gene product with the madB and madC gene products. Thus all three genes appear to have mutual interactions, presumably because of their close physical association in a photoreceptor complex.
非线性系统辨识的正弦波叠加法已应用于毛霉游动孢子囊柄的光生长响应。在毛霉跟踪机上对野生型菌株以及在madA、madB和madC基因中受影响的单突变体和双突变体进行了实验。将正弦波叠加测试刺激施加于光强的对数上。对数平均强度水平为10^(-1) W m^(-2)，波长为477 nm。系统辨识结果以一阶和二阶频率核的形式呈现，它们与出现在维纳泛函级数中的时间核相关。一阶核与先前通过白噪声法获得的结果吻合良好。特别是，madA madB和madB madC双突变体表现出非常微弱的响应。凭借正弦波叠加法的卓越精度，我们获得了足够的分辨率来测量和分析它们的二阶核。一阶和二阶频率核通过涉及非线性参数模型的系统分析方法进行解释。此外，还测试了一个关于基因产物相互作用的非参数假设。相互作用测试的结果证实了先前关于madB和madC基因产物相互作用的结论。此外，随着精度的提高以及向非线性分析的扩展，我们发现了madA基因产物与madB和madC基因产物相互作用的证据。因此，所有这三个基因似乎都存在相互作用，大概是因为它们在光感受器复合物中紧密的物理关联。
