Revealing the functional modularity of yeast transcriptional regulatory network by using a novel topological measurement

It has been reported that function implementations in biological systems, including transcriptional regulatory networks (TRN), show modular architecture. Analyzing functional modularity of biological networks can describe characteristics of function implementation and their "position" in biology systems from the systems perspective. Defining functional modules naturally, we bring up a novel measurement, cohesive degree (CD), to characterize the modularity. From this character, we know that not all of the corresponding modules of function annotations take on good modularity. Considering the ratio of the non-cohesive (zero-CD value) modules, TRN\´s functional modularity is also weaker than that of other biological network and integral ones. And, this is not caused by data integrity, but by the topology of itself. In fact, the modularity implementation of biological systems is mainly accomplished through the cooperation of several types of networks, not by TRN alonely.