(A–B); Injection of peptidoglycan triggers a reversible accumulation of mature oocytes (stage14). (A); 6 hours (6h) post-treatment (p.i.), stage 14 oocytes accumulate in the ovaries of peptidoglycan-injected flies. Transmission light microscopy images of ovaries dissected from control flies (water injected) or peptidoglycan-injected animals 6h post-treatment. (B); peptidoglycan injection modifies the quantity and quality of oocytes by 6 h, leading to an accumulation of mature stage (stage14) eggs. The dynamic over three different time points (6h-24h-48h) post-treatment was assayed. (C–E); pLB1+ neurons reduced activity leads to stage 14 oocyte accumulation. (C); The conditional inactivation of pLB1+ neurons reduces egg-laying. At 21°C, the ubiquitously produced Gal80ts inactivates the Gal4 and thus the Kir 2.1 protein expression. At 29°C, the Gal80ts doesn’t inactivate the Gal4, leading to the inhibited activity of pLB1+ neurons via Kir2.1. Switching back the animals to 21°C inhibits the Gal4 activity via Gal80ts. (D); Conditional inactivation of the pLB1+ neurons triggers a reversible stage 14 oocytes accumulation. Ovaries images of pLB1-Gal4/Tub-Gal80ts, UAS-Kir2.1 flies were acquired with transmission light microscopy for 4 days at two different temperatures. (E); pLB1+ neurons conditional inactivation modifies the quantity and quality of oocytes,leading to an accumulation of stage 14 oocytes. The dynamic over four different time points and two different temperatures is shown. It is important to note that the switch from 21°C to 29°C might be stressful for all the lines since stage 14 oocytes accumulated in all of them. In (A and D), a prototypical stage 14 oocyte is indicated with a red asterisk. In (B), shown are the average numbers over time of different oocyte stages ± SEM from two cumulated independent trials with at least 18 females per genotype and condition used. In (C), shown are the average numbers of eggs laid per fly per 24h ± SEM over 5 days from two cumulated independent trials with at least 59 females per genotype and condition used. In (E), shown are the average numbers of different oocyte stages ± SEM over 4 days for one representative assay out of two independent trials with at least 10 females per genotype and condition used. For (B) and (E), on the x axis, 1–6 corresponds to early stages (from stage 1 to stage 6)oocytes ; 7–9 corresponds to the sum of stages 7, 8 and 9; 10 is for stage 10; 11–13 is for the sum of stages 11, 12 and 13; 14 is for stage 14 and Apo is for apoptotic events, all identified via DAPI staining. * indicates p<0.05; ** indicates p<0.01; *** indicates p<0.0001; + and # indicate statistically significant differences between the test and the controls, but not all of them (see detailed statistics for Figure 9E). In (B), non-parametric t-test, Mann-Whitney test; in (C and E), non-parametric ANOVA, Dunn’s multiple comparison test between the genotypes or treatments. Details including n values and genotypes can be found in the detailed lines, conditions and, statistics for the figure section.