cyp6a17 Is Required for TPB in Drosophila Figure 6. Effects of cyp6a17 knockdown in surface glia cells and the mushroom bodies. (A) cyp6a17 was knockdowned by RNAi in surface glia by cyp6a17SG-Gal4. (B–C) cyp6a17 RNAi knockdown by two mushroom body-specific Gal4 lines, OK107-Gal4(B) and c772-Gal4 (C), causes significant TPB defects in the distribution profiles and AI. Black bars, AIHigh; grey bars, AILow. Two asterisks, P,0.001. doi:10.1371/journal.pone.0029800.g006 outcrossed at least four times, but the effect of UAS-cyp6a17/+ in reducing the AIHigh still remained. It is unknown why this strain shows non-specific low AIHigh. Importantly, however, transgenic overexpression of Cyp6a17 in the presence of Gal4 restores the low AILow defect of the cyp6a17D173 mutant (Fig. 5C). Previous studies have shown that increased levels of cAMP or PKA signaling cause stronger avoidance from low temperature whereas lower cAMP- PKA signaling levels result in the opposite trend with reduced avoidance. This is consistent with our data that cyp6a17 mutants show lower AILow. cyp6a17 is necessary for TPB but may not be sufficient to induce AIHigh. Since cyp6a17 is the only one of multiple downstream factors for PKACA, it may need additional PKA downstream factors to induce AIHigh. It has been reported that many cytochrome P450 proteins are expressed in the midgut, malpighian tubules and fat body whereas only one gene cyp4g15 is detected in the brain of developing larvae PLoS ONE | www.plosone.org 8 December 2011 | Volume 6 | Issue 12 | e29800