Fig 1.
Graphic representation of the study design for field colonies.
Fig 2.
Graphic representation of the study design for laboratory cage assay.
Table 1.
Primers used in the present study.
Fig 3.
Expression levels of N. ceranae 16S rRNA.
The transcriptional activity of N. ceranae 16S rRNA was corresponding with the level of spore loads in infected bees. The relative expression of N. ceranae 16S rRNA in forager bees was significantly higher than in nurse bees under both high- and low- levels of infection (1.2 M vs 26 M N. ceranae spores per bee). The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and an asterisk (*) denotes a statistically significant difference between the two groups (P ≤ 0.05, Student’s t-test).
Fig 4.
Tissue specific total amount of iron in gut and fat body tissues of nurse and forager bees.
An asterisk (*) denotes a statistically significant difference between the two groups (p ≤ 0.05).
Fig 5.
Tissue-specific relative transferrin mRNA transcript level in gut and fat body tissues of nurse forager bees.
The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and an asterisk (*) denotes a statistically significant difference between the two groups (P ≤ 0.05).
Fig 6.
The relative expression of transferrin after treatment of AmTsf -dsRNA.
The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and the different lower-case letters above bars indicate the statistically significant difference among different groups (P ≤ 0.05, ANOVA and Tukey´s tests).
Fig 7.
The relative expression of N. ceranae 16S rRNA after treatment of AmTsf -dsRNA.
The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and the different lower-case letters above bars indicate the statistically significant difference among different groups (P ≤ 0.05, ANOVA and Tukey´s tests).
Fig 8.
Total amount of iron in bees on day 6 and day 12 post AmTsf -dsRNA treatment.
A star denotes a calibrator and the different lower-case letters above bars indicate the statistically significant difference among different groups (P ≤ 0.05, ANOVA and Tukey´s tests).
Fig 9.
Time dependent transcription profiles for genes encoding antimicrobial immune peptides.
(A) Apidaecin, (B) Abaecin, and (C) for gene encoding inhibitor of apoptosis Birc5. The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and the different lower-case letters above bars indicate the statistically significant difference among different groups (P ≤ 0.05, ANOVA and Tukey´s tests).
Fig 10.
Transcript levels for RNA-induced silencing complex components.
(A) Argonaute. (B) Dicer. The relative expression was expressed as an n-fold difference relative to the calibrator (marked by a star) by 2–∆∆Ct method. A star denotes a calibrator and the different lower-case letters above bars indicate the statistically significant difference among different groups (P ≤ 0.05, ANOVA and Tukey´s tests).
Fig 11.
Kaplan–Meier survival curves for the three experimental groups (N = 90 bees/group).
Data represent percentage of survival for the four groups over 12 days of experimental observation. Group I: Nosema-infected bees (infected/untreated); Group II: Nosema-infected bees + AmTsf -dsRNA treatment (infected/treated); Group III: Healthy bees (uninfected/untreated) and Group IV: Nosema-infected bees + GFP-dsRNA. Knockdown of the honey bee transferrin gene reduced the incidence of death (p< 0.05 by Wilcoxon test <p = 0.0041> and Log-rank test <P = 0.0033>).