We are interested in how genes encode behavior. To address this question we are examining control of locomotory behavior and its modulation by sensory input. The C. elegans male is a good model for addressing this question as during male mating behavior a number of alterations occur in the normal sinusoidal movement pattern. We are particularly interested in the early steps of mating behavior, response, backing and turning as this is when the most dramatic changes in locomotory behavior occur. When a male contacts a hermaphrodite he presses the ventral side of his tail against the hermaphrodite and initiates backing behavior. If he reaches the end of the hermaphrodite without contacting the vulva, he turns around the hermaphrodite and continues backing on the other side. When the vulva is reached, the male stops backward locomotion inserts his spicules and transfers sperm. In an attempt to dissect the neural circuits and signaling pathways controlling response, backing and turning behavior we have performed an F2 clonal screen for mutations that disrupt mating behavior. From this screen, eight mutations were isolated that disrupt these early steps of mating behavior. We are currently focusing on one of these mutations,
sy682 , that disrupts response and vulva location behavior. 93% of
sy682 males are defective in response and 42% for vulva location in comparison to 16.7 % response defective and 0% vulva location defective seen in wild type males assayed on the same days. Specifically, these males touch many hermaphrodites before responding and pass the vulva more times before stopping than wild type males. We are additionally studying
cod-5 , a mutant isolated in a mating efficiency screen. Of males homozygous for mutations in
cod-5 , 81% are disrupted in response, 62% are defective in turning and 44% are disrupted in vulva location. Specifically,
cod-5 mutant males take longer than normal to respond to a hermaphrodite. Although males are able to execute a turn correctly they often fail to initiate a turn, backing off of a hermaphrodite and either swimming away or loosely making contact with the other side. Mutant males also have difficulty keeping their tails straight during backing and often briefly back along the lateral side of hermaphrodites. Efforts to map and to determine the genes disrupted in these two mutant lines will be discussed. A more direct approach is also being taken in which the effects of the application of exogenous neurotransmitters on male tail movement and the effect of neurotransmitter synthesis mutants on mating behavior are being examined