C. elegans male mating is comprised of stereotyped steps that can be studied to determine how behavior is regulated. Males mate by locating and positioning their spicules over the hermaphrodites vulva, inserting their spicules, and then transferring sperm. To study how spicule insertion behavior is regulated, we isolated the
sy574 allele that causes males to protract their spicules spontaneously in the absence of mating cues.
sy574 does not cause hermaphrodites or larval males to behave abnormally, but it does cause 58% of virgin males to display the Protraction constitutive (Prc) phenotype. We mapped
sy574 and found that it creates two point mutations in
unc-43, the gene encoding calcium-calmodulin dependent protein kinase II (CaMKII). One
sy574 mutation maps to the catalytic domain while the other mutation is located in the self-association domain. Other
unc-43 alleles display varying degrees of inappropriate spicule protraction as well as other defects that include uncoordinated movement, an inability to mate, and defecation cycle irregularities. However, neither
sy574 males nor hermaphrodites display any other abnormal phenotypes that have been associated with previously characterized
unc-43 alleles, indicating that
sy574 is perturbing functions specific to mating. The erg-like K+ channel
unc-103 has also been shown to be involved in spicule protraction; a null allele (
n1213) results in males that are 42% Prc (Garcia and Sternberg, 2003). Males containing
unc-103(
n1213) and
unc-43(
sy574) are 97% Prc, indicating that the two proteins are acting together in some way to control spicule protraction. UNC-103 is related to EGL-2, a voltage-dependent K+ channel similar to ether-a-go-go channels.
egl-2(gf) does not suppress
unc-103(
n1213), but interestingly, it will suppress the
unc-43(
sy574)-induced Prc phenotype, indicating that
egl-2 is functioning with
unc-43, but not with
unc-103 to control spicule protraction.
egl-2 is expressed in male sex muscles and a subset of neurons. To determine if neuronal and/or muscle function is important for
unc-43s control of spicule protraction, I made double mutants of
unc-43(
sy574) with alleles of neuronal expressed
unc-64-encoded syntaxin, and muscle expressed
lev-11-encoded tropomyosin. I find that
lev-11 mutants that suppress
unc-103(
n1213) premature protraction do not suppress
unc-43(
sy574), but
unc-64 mutants that do not affect
unc-103 alleles can reduce the
unc-43(
sy574) phenotype. We suggest that neuronal function is required for
unc-43 to control spicule protraction, and that
unc-103 and
unc-43 may be acting in parallel pathways.