A cGMP-dependent K+ channel in the Blastocladiomycete fungus Blastocladiella emersonii

• Grant number: 15/17896-2
• Support Opportunities: Regular Research Grants - Publications - Scientific article
• Start date: October 01, 2015
• End date: March 31, 2016
• Field of knowledge: Biological Sciences - Biochemistry - Biochemistry of Microorganisms
• Principal Investigator: Suely Lopes Gomes
• Grantee: Suely Lopes Gomes
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil

Abstract

Phototaxis in flagellated zoospores of the aquatic fungus Blastocladiella emersonii depends on a novel photosensor BeGC1 comprised by a type I (microbial) rhodopsin fused to a guanylyl cyclase catalytic domain that produces the conserved second messenger cGMP. The rapid and transient increase in cGMP levels during zoospore exposure to green light was shown to be necessary for phototaxis and dependent on both, rhodopsin function and guanylyl cyclase activity. Noteworthy, BeGC1 was localized to the zoospore eyespot apparatus, consistent with its role in the phototactic response. A putative cyclic nucleotide gated channel (BeCNG1) was also identified in the genome of the fungus and 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, as well as the rhodopsin-guanylyl cyclase fusion protein, while both of these genes are absent in non-flagellated fungi. The presence of these genes as a pair seems to be exclusive of blastocladiomycete fungi. Taken together, these data demonstrate that 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. (AU)