Characterization of a broad-based mosquito yeast interfering RNA larvicide with a conserved target site in mosquito semaphorin-1a genes

Keshava Mysore,Molly Duman-Scheel,Na Wei,Jacob S Realey,Longhua Sun,Chien-Wei Wang,Limb K Hapairai,Ping Li,David W Severson,Nicholas D Scheel

doi:10.1186/s13071-019-3504-x

Keshava Mysore, Molly Duman-Scheel + Show 8 more

Open Access

https://doi.org/10.1186/s13071-019-3504-x

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Abstract

BackgroundRNA interference (RNAi), which has facilitated functional characterization of mosquito neural development genes such as the axon guidance regulator semaphorin-1a (sema1a), could one day be applied as a new means of vector control. Saccharomyces cerevisiae (baker’s yeast) may represent an effective interfering RNA expression system that could be used directly for delivery of RNA pesticides to mosquito larvae. Here we describe characterization of a yeast larvicide developed through bioengineering of S. cerevisiae to express a short hairpin RNA (shRNA) targeting a conserved site in mosquito sema1a genes.ResultsExperiments conducted on Aedes aegypti larvae demonstrated that the yeast larvicide effectively silences sema1a expression, generates severe neural defects, and induces high levels of larval mortality in laboratory, simulated-field, and semi-field experiments. The larvicide was also found to induce high levels of Aedes albopictus, Anopheles gambiae and Culex quinquefasciatus mortality.ConclusionsThe results of these studies indicate that use of yeast interfering RNA larvicides targeting mosquito sema1a genes may represent a new biorational tool for mosquito control.

Highlights

RNA interference (RNAi), which has facilitated functional characterization of mosquito neural develop‐ ment genes such as the axon guidance regulator semaphorin-1a, could one day be applied as a new means of vector control
S. cerevisiae expressing short hairpin RNA (shRNA) corresponding to the sema1a gene kill Ae. aegypti larvae small interfering RNAs (siRNA) #460, which corresponds to a conserved target sequence in mosquito sema1a genes (Additional file 2: Table S1), was uncovered in an Ae. aegypti siRNA soaking screen for larval lethal genes [25]
Screen data from two replicate experiments (n = 20 larvae/replicate) were combined and assessed with the Fisher’s exact test. shRNAs corresponding to the #460 or control siRNA sequences were expressed in S. cerevisiae from a plasmid (b) or following integration of two copies of the shRNA expression cassettes into the S. cerevisiae genome (c)

Summary

Introduction

RNA interference (RNAi), which has facilitated functional characterization of mosquito neural develop‐ ment genes such as the axon guidance regulator semaphorin-1a (sema1a), could one day be applied as a new means of vector control. We describe characterization of a yeast larvicide developed through bioengineering of S. cerevisiae to express a short hairpin RNA (shRNA) targeting a conserved site in mosquito sema1a genes. When used in Mysore et al Parasites Vectors (2019) 12:256 and high levels of resistance have been observed in larvae collected in the field (reviewed in [18]). High levels of Bti resistance have been observed in C. pipiens larvae [19]. ITNs and IRS have been the backbone for malaria vector control, resistance to insecticides used in these applications is an increasing problem [20], and neither intervention can combat Anopheles mosquitoes that bite or rest outdoors [20]

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