<i>grk-2</i> acts in the ciliated neurons to control exploration behavior.

(A) Expression of grk-2 cDNA under a pan-neuronal promoter rescues the exploration defect of grk-2 mutant animals in the presence of food. The grk-2 cDNA was expressed in grk-2(gk268) mutant animals under a pan-neuronal promoter (rab-3p, transgene yakEx44), ventral cord acetylcholine motor neuron promoter (acr-2p, transgene yakEx47), and interneuron promoter (nmr-1p, transgene yakSi32). Shown is the number of squares single animals covered in ~20 h. (****, P0.05. One way ANOVA followed by a Bonferroni test. Error bars = SEM; n = 20–25). (B) Expression of grk-2 cDNA under either of two ciliated sensory neuron promoters (xbx-1p, transgene yakEx71 and osm-6p, transgene yakEx53) rescues the exploration defect of grk-2(gk268) mutant animals in the presence of food. (****, P0.05. One way ANOVA followed by a Bonferroni test. Error bars = SEM; n = 20–30). (C) Expression of grk-2 cDNA under a ciliated sensory neuron promoter (xbx-1p::grk-2, transgene yakEx71) rescues the dispersal defect of grk-2(gk268) in the absence of food. (****, P0.05. One way ANOVA followed by a Bonferroni test. Error bars = SEM; n = 49–55). Please note the high variability in the off-food response in comparison to the on-food response (Fig 2B). This could be because worms are more mobile in the absence of food and constantly searching for a food source, which would increase the variability of the distances they cover. (D) Expression of grk-2 cDNA under the odr-3 promoter (expression in AWA, AWB, AWC, ASH, and ADF neurons; odr-3p::grk-2, transgene yakEx189) partially rescues the exploration defect of grk-2(gk268). (****, Pgrk-2 cDNA under the sra-6 promoter (expression in ASH and ASI neurons; sra-6p::grk-2, transgene yakEx191) or under the combined control of the odr-10 (AWA neurons), str-1 (AWB neurons) and str-2 (AWC ON neuron) promoters (str-1p, str-2p, odr-10p::grk-2, transgene yakEx194) partially rescues the exploration defect of grk-2(gk268). (****, Pgrk-2 cDNA under the odr-10p (AWA), str-1p (AWB), or str-2p (AWC ON) promoters (transgenes pekEx267, pekEx265 and pekEx266, respectively) partially rescues the grk-2 exploration defect. (***, Pgrk-2 mutant are the same as in Fig 3B (these experiments were run in parallel). (G) grk-2 is expressed in many neurons in the head of the worm including odr-3- expressing neurons. Representative images of the z-stack projections of the head of an animal co-expressing tagRFP fused to GRK-2 ORF driven by the grk-2 promoter (grk-2::tagRFP, transgene yakIs19) and NLS-tagged mNeon driven by the odr-3 promoter (odr-3p::mNeon::NLS; transgene yakEx204). Arrows indicate grk-2::tagRFP-expressing cells that also express odr-3p::mNeon::NLS. Scale bar: 10 μm. (H) Expression of grk-2 cDNA under the gcy-8 promoter (expression in AFD neurons; gcy-8p::grk-2, transgene yakEx202) fails to rescue the exploration defect of grk-2(gk268). (ns, P>0.05. One way ANOVA followed by a Bonferroni test. Error bars = SEM; n = 20–40). (I) Expression of grk-2 cDNA under the dat-1 promoter (expression in dopaminergic neurons; dat-1p::grk-2, transgene yakEx259) fails to rescue the exploration defect of grk-2(gk268). (ns, P>0.05. Student’s t-test. Error bars = SEM; n = 38–44). (J) Expression of grk-2 cDNA under the heat shock promoter hsp-16.41 (hsp-16.41p::grk-2, transgene yakEx253) in adult grk-2(gk268) partially but significantly rescues their exploration defect. (****, P<0.0001. Student’s t-test. Error bars = SEM; n = 34–44).