A screen for Neurospora knockout mutants displaying growth rate dependent branch density

Branch density (the spatial distribution of branch initiation points along a growing hypha) in wild-type Neurospora has been shown to remain constant at different growth rates due to a hypothesized system which compensates for hyphal growth rate. Here we report the results of a survey of the Neurospora knockout library for mutants affecting this proposed growth rate compensation system. The mutants identified fail to maintain branching homeostasis?at different growth rates, thus showing growth rate-dependent branch density. The gene functions highlighted by this screen are diverse with several emerging themes including: ubiquitin-binding proteins, kinases, metal binding/metal metabolism proteins, reactive oxygen species (ROS) control proteins, and clock-associated/clock-controlled proteins. Other than their common influence on branch density homeostasis, the relationships between these gene functions and how they interact to influence branching are unclear.