Meeting Abstract
Complex sensory suites often underlie critical behaviors, including avoiding predators or locating prey, mates, and shelter. Multisensory systems that control motor behavior even appear in unicellular eukaryotes, such as Chlamydomonas, which are important laboratory models for sensory biology. However, we know of no unicellular opisthokont models that control motor behavior using a multimodal sensory suite. Therefore, existing single-celled model organisms for studying multimodal sensorimotor integration are very distantly related to animals. Here, we describe a multisensory system that controls the motor function of unicellular, zoospores of a fungus. We find zoospores of Allomyces arbusculus exhibit both phototaxis and chemotaxis. While swimming, they move towards light and settle on cellulose membranes exuding combinations of particular amino acids. Furthermore, we report that closely related Allomyces species do not share this multisensory system. Instead, each respond to only one of the two stimuli detected by A. arbusculus. This diversity of sensory modalities within Allomyces provides a rare example of a comparative framework that can be used to examine the evolution of sensory systems after the gain or loss of individual senses. Taking advantage of this newfound system, we examine the molecular pathways co-opted during sensory integration within zoospores. The tractability of Allomyces and related fungi as laboratory organisms will allow detailed mechanistic investigations into how sensory systems may have functioned in early opisthokonts before multicellularity allowed for the evolution of specialized cell types.
