Phenotypic plasticity, trade-offs and gene expression changes accompanying dietary restriction and switches in Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

Abstract

In this study, we investigated the effects of dietary restriction (DR) and variable diets on phenotypes and gene expression in oriental fruit fly, Bactrocera dorsalis (Hendel), one of the most economically important pests in the family Tephritidae around the world. As expected, we found that DR altered the B. dorsalis phenotypes by significantly increasing stress resistance and lifespan, but reduced egg production when compared with the control diet. The results suggested a trade-off between reproduction versus somatic maintenance (stress resistance) and lifespan in B. dorsalis. Diet also had a significant effect on hatchability, and DR could increase the egg hatching success of B. dorsalis. Furthermore, DR up-regulated metabolic pathways involved in energy homeostasis and down-regulated pathways in egg production, which might mediate trade-offs between somatic maintenance and reproduction under DR regimes. The gene expression profiles in response to the acute dietary switches indicated that the digestive and metabolic pathways maybe involved in the adaptability of flies to variable dietary resources. In summary, the research facilitates a better understanding of the molecular mechanisms responsible for the B. dorsalis' phenotypic adjustments to the different qualities of the available diets.

Figure 1

Survival curves (Each curve represents the cumulative survival probability for each diet treatment) for starvation resistance (A) and desiccation resistance (C), and mean time before death from starvation stress (B) and desiccation stress (D) in Bactrocera dorsalis derived from either dietary restriction (DR) or control diet (CD) regimes. Significant differences between the two treatments were analysed by the independent samples t-test (for comparison of two means) (*P < 0.05, **P < 0.01, ***P < 0.001).

Figure 2

Survival curves (Each curve represents the cumulative survival probability for each diet treatment) for heat shock (A) and cold shock (C), and mean time entering heat shock (B) and cold shock (D) in Bactrocera dorsalis derived from either dietary restriction (DR) or control diet (CD) regimes. Significant differences between the two treatments were analysed by the independent samples t-test (for comparison of two means) (*P < 0.05, **P < 0.01, ***P < 0.001).

Figure 3

Daily hatching rate of eggs laid during a seven day period (A) and mean hatchability of all the eggs laid in 7 days (B) by Bactrocera dorsalis females derived from either dietary restriction (DR) or control diet (CD) regimes from 27 to 33 days after emergence. Each value represents the mean ± SE of three replicates. Significant differences between the two treatments were analysed by the independent samples t-test (for comparison of two means) (*P < 0.05, **P < 0.01, ***P < 0.001).

Figure 4

Daily number of eggs laid per female Bactrocera dorsalis upon dietary switch at day 30 after emergence. Each value represents the mean ± SE of five replicates (A). Mean number of eggs laid in 13 days, from 26 to 38 days after emergence, per female Bactrocera dorsalis under chronic dietary restriction (DR) and control diet (CD) regimes (B). Significant differences between the two treatments were analysed by the independent samples t-test (for comparison of two means) (*P < 0.05, **P < 0.01, ***P < 0.001).

Figure 5

Survival curves (Each curve represents the cumulative survival probability for each diet treatment) for Bactrocera dorsalis adults upon dietary switch at day 30 after emergence (A). Mean lifespans of Bactrocera dorsalis adults fed on chronic dietary restriction (DR) and control diet (CD) (B). Significant differences between the two treatments were analysed by the independent samples t-test (for comparison of two means) (*P < 0.05, **P < 0.01, ***P < 0.001).