Meeting Abstract
Understanding the evolution of complex traits has piqued the interest of the scientific community for decades. However, it is difficult to identify clades simple enough to allow for easy manipulation, yet with enough diversity to display multiple sensory modalities across a manageable taxonomic distance. An early diverging lineage of fungi, genus Allomyces, reproduces via motile zoospores. These zoospores must rely on external cues in order to move towards, and settle at, a favorable location. Previous literature has demonstrated that Allomyces zoospores are known to respond to either light or chemical stimuli. I investigated the evolutionary history and zoospore-specific sensory suites in three species: A. reticulatus (AR), A. arbuscula (AA), and A. macrogynus (AM). Behavioral experiments revealed that zoospore movements of AR are guided solely by phototaxis; AM are guided only by chemotaxis; AA rely on both photo- and chemotaxis. Further analysis showed differences in the ability/preference of AA and AM zoospores in response to amino acid gradients. Phototactic behavior in AA is preferentially sensitive to Blue(480nm) and Green(530nm) over Red(600nm) light; a similar action spectrum to AR zoospores. My comparisons of new AR transcriptomic data and existing AM genomic data found an Opsin/Guanylyl-cyclase fusion gene(OpGC) present in both species. PCR showed no evidence of OpGC expression in AM zoospores. This, along with species-specific differences in the side-body complex, may have led to loss of photoreception in AM. Informed by a phylogenetic analysis of Blastocladiomycota, I conclude that there have been several critical shifts in zoospore sensory suites throughout the phylum.
