FIGURE 1.

ETH signaling regulates Drosophila courtship LTM. (A) Schematic of the long-term courtship conditioning procedure. (B) ETH deficiency was created by ablation of Inka cells through conditional ectopic expression of apoptosis genes hid and rpr under the control of RU486-activated GeneSwitch GAL4. Transgenic animals show significant reduction of MPI when treated with RU486 as compared to controls (n = 54–56). (C) Conditional block of vesicular secretion by Inka cells was achieved through expression of temperature-dependent dynamin mutant shibire in Inka cells. Courtship conditioning was conducted at the restrictive temperature, while testing occurred at room temperature. Transgenic flies exhibit less suppression of courtship activities following training than those of control groups (n = 48–52). Activation of adult Inka cells during 3- (D), and 1-h (D′) training with a mated female at 31°C utilizing dTrpA1 overexpression. ETH-GAL4/UAS-dTrpA1 males show 22.5% (D) and 16.9% (D′) courtship suppression following 3- and 1-h training at 31°C, respectively, compared to sham-trained males (n = 60–80). Light blue bars indicate MPI levels attained following a 5-h training protocol at 21°C, whereas dark blue bars depict significant reduction of MPI levels following 3- (D) or 1-h (D′) training protocols at 21°C. (E) Effect of Inka cell activation during 5-h training on persistence of memory performance. Training and sham-training of all animals were performed at 31°C. Asterisks represent statistical differences between data from test groups and GAL4 and UAS genetic control groups (n = 64–78). Mann–Whitney U test for CI and random permutation test for MPI; *p < 0.05, **p < 0.01, and ***p < 0.001. ns, no significance.