In C. elegans there are over 1000 putative GPCR genes, of which approximately 18 are predicted to code for rhodopsin-like G protein-coupled receptors (GPCRs). Heterotrimeric GTP-binding proteins mediate the response to a wide variety of neurotransmitters and hormones, all of which bind to GPCRs. I have chosen to work on M03F4.3, which is a candidate rhodopsin-like GPCR. Although M03F4.3 is believed to code for rhodopsin-like GPCR, its functions are not yet clear. To investigate its functions, a region upstream of the M03F4.3 putatively containing the complete promoter has been stitched to GFP-encoding DNA and injected into C. elegans hermaphrodites to create transgenic animals. Thus, the expression patterns can be observed with GFP fluorescence. Expression was observed in anterior deirid and cephalic sensilla, vulva, intestine, rectum gland cells, and one of posterior neurons. The anterior deirid sensilla and the cephalic sensilla comprise two ADE neurons and two CEP neurons, respectively, which are known to be involved in dopamine synthesis/expression. In addition, a BLASTp search has revealed that C. elegans genes K09G1.4 (
dop-2 ), F15A8.5 (
dop-1 ), C02D4.2 (
ser-2 ), K02F2.6 (
ser-3 ), Y22D7AR.13 (
ser-4 ), and C09B7.1 (
ser-7 ) share high similarities, based on amino acid sequence, with M03F4.3. The expression pattern of K09G1.4 is similar to M03F4.3, which makes M03F4.3 a good candidate for expression of dopamine receptor. Furthermore, the regulatory elements that govern the expression of M03F4.3 were investigated by constructing a series of deletions in promoter region to GFP and thus injected into C. elegans hermaphrodites. The regulatory elements for transcription in the anterior end and the intestine lie between ~200bp and ~450bp on the promoter upstream of M03F4.3. Furthermore, the regulatory elements for transcription in the posterior end are both upstream of ~1450bp and between ~950bp and ~450bp. The promoter upstate of ~1450bp contains regulatory elements that governs the expression in the vulva. In addition, experiments with M03F4.3 knockout and
dop-1 ,
dop-2 ,
ser-2 ,
ser-3 , or
ser-7 RNAi constructs have been conducted to determine any changes in social and mating behaviors, locomotion and morphology of both hermaphrodites and males. No changes, however, have been detected. The findings, particularly based on BLASTp and GFP expression results, suggest that M03F4.3 is a likely candidate to code for a dopamine receptor.