title: A Cyclic GMP-Dependent K+ Channel in the Blastocladiomycete Fungus Blastocladiella emersonii.
abstract: Phototaxis in flagellated zoospores of the aquatic fungus Blastocladiella emersonii depends on a novel photosensor, Blastocladiella emersonii GC1 (BeGC1), comprising a type I (microbial) rhodopsin fused to a guanylyl cyclase catalytic domain, that produces the conserved second messenger cyclic GMP (cGMP). The rapid and transient increase in cGMP levels during the exposure of zoospores to green light was shown to be necessary for phototaxis and dependent on both rhodopsin function and guanylyl cyclase activity. It is noteworthy that BeGC1 was localized to the zoospore eyespot apparatus, in agreement with its role in the phototactic response. A putative cyclic nucleotide-gated channel (BeCNG1) was also identified in the genome of the fungus and was implicated in flagellar beating via the action of a specific inhibitor (l-cis-diltiazem) that compromised zoospore motility. Here we show that B. emersonii expresses a K(+) channel that is activated by cGMP. The use of specific channel inhibitors confirmed the activation of the channel by cGMP and its K(+) selectivity. These characteristics are consistent with the function of an ion channel encoded by the BeCNG1 gene. Other blastocladiomycete fungi, such as Allomyces macrogynus and Catenaria anguillulae, possess genes encoding a similar K(+) channel and the rhodopsin-guanylyl cyclase fusion protein, while the genes encoding both these proteins are absent in nonflagellated fungi. The presence of these genes as a pair seems to be an exclusive feature of blastocladiomycete fungi. Taken together, these data demonstrate that the B. emersonii cGMP-activated K(+) channel is involved in the control of zoospore motility, most probably participating in the cGMP-signaling pathway for the phototactic response of the fungus.
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Gabriela Mól
authors.initials: GM
authors.lastname: Avelar
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Talita
authors.initials: T
authors.lastname: Glaser
authors.affiliation: Biosciences, University of Exeter, Exeter, United Kingdom.
authors.forename: Guy
authors.initials: G
authors.lastname: Leonard
authors.affiliation: Biosciences, University of Exeter, Exeter, United Kingdom Integrated Microbial Biodiversity Program, Canadian Institute for Advanced Research (CIFAR), Toronto, ON, Canada.
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Richards
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil.
authors.forename: Henning
authors.initials: H
authors.lastname: Ulrich
authors.affiliation: Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, São Paulo, Brazil sulgomes@iq.usp.br.
authors.forename: Suely L
authors.initials: SL
authors.lastname: Gomes
mesh_terms: D055133:Blastocladiomycota / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D006152:Cyclic GMP / Q000378:metabolism; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics / Q000378:metabolism*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism*; D013172:Spores, Fungal / Q000378:metabolism
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D005656:Fungal Proteins; D015221:Potassium Channels; D006152:Cyclic GMP; D011188:Potassium