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The cuticle, an essential structure for insects, is produced from cuticular proteins and chitin via a series of biochemical reactions. Tweedle genes are important members of the cuticular protein family and have four conserved motifs binding to chitin. Tweedle family genes have been found to play a profound effect on cuticle development. Here, we report that the cuticular protein gene LmTwdl1 of Locusta migratoria belongs to the Tweedle family. In situ hybridization showed that LmTwdl1 is localized to epidermal cells of the cuticle. The expression patterns of LmTwdl1 showed low expression in the cuticle during the early and middle stages of the fifth-instar nymphs; in contrast, its expression rapidly increased in the late stages of fifth-instar nymphs. We performed RNA interference to examine the function of LmTwdl1 in locusts. Silencing of LmTwdl1 resulted in high mortality during the molting process before the next stage. Also, the epicuticle of nymphs failed to molt, tended to be thinner and the arrangement of chitin in the procuticle appeared to be disordered compare to the control group. These results demonstrate that LmTwdl1 plays a critical role in molting, which contributes to a better understanding of the distinct functions of the Tweedle family in locusts. [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]

The cytochrome P450 monooxygenase (cytochrome P450) gene superfamily comprises many genes that may be involved in the biotransformations of pesticides and other xenobiotics. To date, very little is known about cytochrome P450 genes in the oriental migratory locust, Locusta migratoria manilensis. In this study, we carried out a genome-wide analysis of cytochrome P450 genes of the locust to identify putative cytochrome P450 genes and characterize their expression responses to insecticide exposures. We identified 15 cytochrome P450-like genes from a locust expressed sequence tag database (LocustDB). Reverse transcription polymerase chain reaction (RT-PCR) analysis showed that most cytochrome P450-like genes displayed different tissue and developmental stage expression patterns. However, most of them were predominantly expressed in the midgut, gastric caeca, fatbodies, and/or hindgut. Biochemical analysis showed that cytochrome P450 was differentially affected by three different insecticides. Deltamethrin caused significant inductions in 12 h at LD30 (dose to kill 30% of the tested individuals) in the nymphs, whereas malathion and carbaryl did not have significant effect on cytochrome P450 enzyme activity. Further RT-PCR analysis showed significant increases of transcriptions of several cytochrome P450 genes in deltamethrin-treated locusts. Thus, the increased cytochrome P450 enzyme activity is likely due to increased transcriptions of multiple cytochrome P450 genes in response to deltamethrin exposure. These results are expected to help us better understand the interactions between insecticides and major detoxification enzymes, and possible changes of the susceptibility to other insecticides in deltamethrin-treated insects at various molecular levels. [ABSTRACT FROM AUTHOR]