Transcriptomic analysis of s-methoprene resistance in the lesser grain borer, Rhyzopertha dominica, and evaluation of piperonyl butoxide as a resistance breaker
Background: The lesser grain borer, Rhyzopertha dominica is a serious pest of stored grains. Fumigation and contact insecticides play a major role in managing this pest globally. While insects are developing genetic resistance to chemicals, hormonal analogues such as s-methoprene play a key role in reducing general pest pressure as well as managing pest populations that are resistant to fumigants and neurotoxic contact insecticides. However, resistance to s-methoprene has been reported in R. dominica with some reports showing a remarkable high resistance, questioning the use of this compound and other related analogues in grain protection. The current study attempts to identify possible molecular mechanisms that contribute in resistance to s-methoprene in R. dominica.
Results: Transcriptome analysis of resistant and susceptible strains of this pest species identified a set of differentially expressed genes related to cytochrome P450s, indicating their potential role in resistance to s-methoprene. Laboratory bioassays were performed with s-methoprene treated wheat grains in presence and absence of piperonyl butoxide (PBO), a cytochrome P450 inhibitor. The results indicate that PBO, when applied alone, at least at the concentration tested here, had no effect on R. dominica adult emergence, but has a clear synergistic effect to s-methoprene. The number of produced progeny decreased in presence of the inhibitor, especially in the resistant strain. In addition, we also identified CYP complement (CYPome) of R. dominica, annotated and analysed phylogenetically, to understand the evolutionary relationships with other species.
Conclusions: The information generated in current study suggest that PBO can effectively be used to break resistance to s-methoprene in R. dominica.
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Additional file 1, Figure S1: Mean mortality (±SEM) of Rhyzopertha dominica after 7, 14 and 21 days of exposure for the susceptible (Lab-S) and resistant (Met-R) strain for all the combinations tested (control, 0.01 mg/kg, 0.03 mg/kg, 0.1 mg/kg, 0.3 mg/kg, PBO, 0.01 mg/kg + PBO, 0.03 mg/kg + PBO, 0.1 mg/kg + PBO, 0.3 mg/kg + PBO for susceptible and control, 1 mg/kg, 3 mg/kg, 10 mg/kg, 30 mg/kg, PBO, 1 mg/kg + PBO, 3 mg/kg + PBO, 10 mg/kg + PBO, 30 mg/kg + PBO for resistant).
Additional file 2, Figure S2: Principal components analysis of the transcript expression levels between the resistant (Met-R - blue) and susceptible (Lab-S - red) strains. The two strains are clearly different from each other, a prerequisite for downstream analyses.
Additional file 3, Table S1: Corresponding information regarding sequence identity of CYPs.
Additional file 4, Table S2: Details of all up- and down-regulated genes between the resistant Met-R and the susceptible Lab-S strains (padj <0.001, log2|FC| >2).
Additional file 5, Table S3, Amino acid sequences used in the phylogenetic study of the R. dominica P450s, presented in Fig. 4.
Additional file 6, Table S4: Primers used for the validation qPCRs.
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Transcriptomic analysis of s-methoprene resistance in the lesser grain borer, Rhyzopertha dominica, and evaluation of piperonyl butoxide as a resistance breaker
Posted 30 Dec, 2020
On 13 Dec, 2020
On 13 Dec, 2020
On 13 Dec, 2020
On 07 Dec, 2020
On 28 Nov, 2020
On 28 Nov, 2020
On 28 Nov, 2020
On 21 Sep, 2020
On 21 Sep, 2020
Received 21 Sep, 2020
On 16 Sep, 2020
Invitations sent on 16 Sep, 2020
On 15 Sep, 2020
On 15 Sep, 2020
On 18 Jun, 2020
Received 30 May, 2020
On 14 May, 2020
On 12 May, 2020
Received 26 Apr, 2020
On 06 Apr, 2020
Invitations sent on 01 Apr, 2020
On 31 Mar, 2020
On 19 Mar, 2020
On 19 Mar, 2020
On 11 Mar, 2020
Background: The lesser grain borer, Rhyzopertha dominica is a serious pest of stored grains. Fumigation and contact insecticides play a major role in managing this pest globally. While insects are developing genetic resistance to chemicals, hormonal analogues such as s-methoprene play a key role in reducing general pest pressure as well as managing pest populations that are resistant to fumigants and neurotoxic contact insecticides. However, resistance to s-methoprene has been reported in R. dominica with some reports showing a remarkable high resistance, questioning the use of this compound and other related analogues in grain protection. The current study attempts to identify possible molecular mechanisms that contribute in resistance to s-methoprene in R. dominica.
Results: Transcriptome analysis of resistant and susceptible strains of this pest species identified a set of differentially expressed genes related to cytochrome P450s, indicating their potential role in resistance to s-methoprene. Laboratory bioassays were performed with s-methoprene treated wheat grains in presence and absence of piperonyl butoxide (PBO), a cytochrome P450 inhibitor. The results indicate that PBO, when applied alone, at least at the concentration tested here, had no effect on R. dominica adult emergence, but has a clear synergistic effect to s-methoprene. The number of produced progeny decreased in presence of the inhibitor, especially in the resistant strain. In addition, we also identified CYP complement (CYPome) of R. dominica, annotated and analysed phylogenetically, to understand the evolutionary relationships with other species.
Conclusions: The information generated in current study suggest that PBO can effectively be used to break resistance to s-methoprene in R. dominica.
Figure 1
Figure 2
Figure 3
Figure 4