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Rab proteins constitute the largest family of small GTPases, which play pivotal roles in intracellular membrane trafficking in all eukaryotes. A number of Rab genes have been identified in eukaryotes; however, very little information about these genes has been reported in insects. In the current study, for the first time we identified and characterized 27 Rab family genes from Locusta migratoria. Phylogenetic analysis and comparison of domain architecture indicated that Rab family genes are highly conserved among insect species. Tissue‐dependent expression profiles indicated that expression of Rab genes was highest in the ovary, except for LmRab3, which was most highly expressed in hemolymph. The biological function of each Rab gene was investigated using RNA interference (RNAi). Double‐stranded RNA targeting each Rab gene was injected into the hemocoel of nymphs and revealed that suppression of two Rab genes (LmRab5 and LmRab11A) caused 100% mortality. In addition, nymphs injected with dsLmRab5 exhibited severe phenotypic defects in the gastric caeca and midgut, while dsLmRab11A arrested the molting process. We then applied the RNAi of RNAi technique to test if silencing either of these two genes would affect the suppression of the lethal giant larvae (LmLgl) reporter gene and found that suppression of LmRab5 diminished the RNAi efficiency of LmLgl, whereas suppression of LmRab11A enhanced RNAi efficiency of LmLgl. These results indicate that Rab genes contribute differently to RNAi efficiency in different tissues. Our study provides a foundation for further functional investigations of Rab genes and their contributions to RNAi efficiency in L. migratoria. [ABSTRACT FROM AUTHOR]

The efficiency of RNA interference (RNAi) varies substantially among different insect species. Rapid degradation of double‐stranded RNA (dsRNA) by dsRNA‐degrading nucleases (dsRNases) has been implicated to cause low RNAi efficiency in several insect species. In this study, we identified four dsRNase genes (OfdsRNase1, OfdsRNase2, OfdsRNase3 and OfdsRNase4) from the Asian corn borer (Ostrinia furnacalis) transcriptome database. Bioinformatic analyses showed that each deduced protein sequence contained endonuclease NS domains and signal peptides. Gene expression analysis revealed that OfdsRNase2 was exclusively expressed in the midgut of larvae. RNAi efficiency was investigated in 2‐d‐old fifth‐instar larvae (high expression of dsRNase2) and 2‐d‐old pupae (low expression of dsRNase2) by feeding or injecting dsRNA targeting a marker gene that encodes the lethal giant larvae protein (OfLgl). Our results showed that OfLgl only partially silenced the expression of OfLgl in pupae, but not in larvae, suggesting that OfdsRNase2 could contribute to lower RNAi efficiency in larval stages. This hypothesis was supported by our RNAi‐of‐RNAi experiment using a tissue culture technique where the silencing efficiency against the reporter gene, OfHex1, was significantly improved after knockdown of OfdsRNase2. When double luciferase assays were performed to evaluate the role of the four dsRNases in vitro, only OfdsRNase2 expressed in S2 cells significantly affected RNAi efficiency by degrading dsRNA. Taken together, our results suggested that the degradation of dsRNA by OfdsRNase2 in the midgut contributed to low RNAi efficiency in O. furnacalis larvae. [ABSTRACT FROM AUTHOR]

Cytochrome P450 monooxygenases (CYPs) play essential physiological functions in insects. CYP303A1 is highly conserved in insect species studied to date, and shows an indispensable role for adult eclosion in both Locusta migratoria and Drosophila melanogaster. However, how CYP303A1 is regulated to control insect developmental processes remains uninvestigated. In this study, we discovered functional binding sites for miR‐184 in the coding sequence of LmCYP303A1. The luciferase reporter assay showed that miR‐184 could target LmCYP303A1 and regulate its expression in vitro. Furthermore, overexpression of miR‐184 through microinjection of agomir to locusts reduced the transcripts of LmCYP303A1 and led to abnormal molting, which is similar to the phenotype of silencing LmCYP303A1 by direct injection of dsLmCYP303A1 to locusts. Meanwhile, down‐regulation of miR‐184 by injection of antagomir increased the LmCYP303A1 transcript and caused molting defects. These findings suggested that miR‐184 could target LmCYP303A1 to regulate the molting process in L. migratoria, which might be considered as a novel target for pest control. [ABSTRACT FROM AUTHOR]

MicroRNAs (miRNAs) are small noncoding RNAs, which participate in many biological processes. The small RNA transcriptome in the migratory locust has been characterized and 50 conserved miRNA families and 185 potential locust-specific miRNA family candidates have been identified using high-throughput sequencing. However, it is unclear whether miRNAs influence a wide variety of locusts' biological processes, such as growth or development. In insects, Dicer1 ribonuclease transforms miRNA precursors into mature miRNAs. Thus, using systemic RNA interference (RNAi) to silence the expression of Dicer1 in the migratory locust, Locusta migratoria, we reduced miRNA contents in the locust and disrupted two types of molt (nymph-nymph, and nymph-adult). The RNAi of LmDicer1 also resulted in a high mortality in L. migratora. Our study revealed that LmDicer1 was essential for miRNA regulation and development of L. migratoria. These results further support our notion that LmDicer1 could serve as an excellent target for developing novel strategies for controlling this important insect pest. [ABSTRACT FROM AUTHOR]