Figure 3.

Sucrose modulated the oviposition preference for fermentation. (a) Females avoided to deposit eggs on the casein-cornmeal-agar media titrated to different sucrose (+Sucrose%) compared to fly food without sucrose (−Sucrose). n = 12, one of two replicates. (b) Sucrose deprivation impaired the oviposition preference for fermentation. Fly food was control food (+sucrose) or deprived of sucrose (−sucrose). The 2-choice cage of each food was assembled with H₂O or bacteria. n = 8, one of three replicates. (c) Sucrose replenishment attenuated this oviposition preference in a dose-dependent manner. Sucrose was added to fermented fly food (EF + Sucrose), and the oviposition preference of EF + sucrose food was compared to fermented food (H₂O). ANOVA tests with LSD post hoc analysis were used to calculate significant differences between columns. n = 12, one of two replicates. (d) The α-glucosidase inhibitor, acarbose, diminished the oviposition preference for fermentation. Acarbose was added to fermented fly food (EF + acarbose), and the oviposition preference of EF + acarbose food was compared to fermented food (H₂O). n = 12, one of two replicates. (e) Bacterial cells were dispensable to trigger the oviposition preference for fermentation. Frozen bacterial cells were supplemented on the surface of one half of fly diet in a 2-choice cage, and ovipositional preference for bacterial cells was compared to fly food with water. n = 12, one of three replicates. (f,g) Fruit flies were averse to laying eggs on the media with LAB metabolites or lactate. n = 12, one of three replicates. Supernatant or lactate was added to one half of fly diet in a 2-choice cage, and the ovipositional preference for them was compared to fly food with water (H₂O), respectively. (h) Sucrose was a more robust factor that suppressed the oviposition of females than EF metabolites or lactate. Females were allowed to choose between 0.5 ml LAB metabolites (Supernatant) or 1% lactate (Lactate) and dosage-dependent sucrose (Sucrose%) using 2-choice food preference assays. High concentration sucrose reversed the avoidance to LAB metabolites and sucrose. n = 12, one of three replicates. (i) The aversion to 5% sucrose (Sucrose) was affected by lactate in a dosage-dependent manner (Lactate%). Significance was calculated by ANOVA tests with LSD post hoc analysis for Fig. 3e and ANOVA tests with LSD post hoc analysis for others. Mean ± SEM. Symbols: NS p > 0.05; *p < 0.05; **p < 0.01; ***p < 0.001.