Figure 1

Induction of mdIV neuron-dependent larval writhing behavior by UV irradiation. (A) Larval writhing behavior in response to UV irradiation. High intensity UVB and UVC exposure induced robust writhing behavior w¹¹¹⁸ 3rd instar larvae. Exposure to UVA did not cause a significant behavioral response. Varied intensities of UVC irradiation resulted in a dose-dependent response(n = 6, 9, 8, 15 and 10, respectively). ***p < 0.0001, one-way ANOVA with Tukey’s post comparison test vs. UVA (B) Transgenic inactivation of the larval visual system in GMR-GAL4/UAS-TNT-G and GMR-hid larvae did not suppress the writhing behavior after exposure to UVC(M)(n = 6 for all). (C) Inactivation of larval mdIV neurons in ppk1GAL4/UAS-TNT-G larvae resulted in a greatly reduced response to both UVC(M) and UVC(H)(n = 6, 6, 5, 9, 9, 11, 6 and 8, respectively). ***p < 0.0001, one-way ANOVA with Tukey’s post comparison test vs ppk1GAL4/+(H/M). (D) ppk1 null mutant(DfA/DfB) larvae showed a strongly reduced response to UVC(M) but responded normally to UVC(H). mdIV neuron-specific expression of PPK1 rescued the larval response to UVC(M)(n = 7, 9, 6, 7 and 6, respectively). ***p < 0.0001, one-way ANOVA with Tukey’s post comparison test vs DfA/DfB(M) (E) painless mutant alleles displayed a reduced sensitivity to UVC(M) with a range of severity consistent with the phenotypic strength of the allelic series. The most severe allele, pain³, responded normally to UVC(H)(n = 14, 15, 6, 8, 9, 8, 27, 10 and 12, respectively). *p < 0.01, **p < 0.0001 ***p < 0.0001, one-way ANOVA with Tukey’s post comparison test vs w¹¹¹⁸(M). All data are presented as mean±SEM. Each N value represents results from one experimental trial using 5 larvae exposed to UVR and visually scoring the percentage responding.