Search

Henosepilachna vigintioctopunctata is a serious insect pest which attacks a large number of nightshades and cucurbits in Asian countries, Brazil and Australia. Prolonged application of traditional pesticides has caused environmental pollution and exerted deleterious effects on human health. Finding new approaches with high target specificity and low environmental contamination has become an urgent task. RNA interference (RNAi) induced by double‐stranded RNA (dsRNA) is expected to be applicable to managing this pest. Here we evaluated the effects of Escherichia coli‐expressed dsRNAs targeting ecdysone receptor (EcR) gene via dietary delivery in laboratory and foliar spraying in a greenhouse. The target transcript was successfully knocked down when the 4th‐instar larvae had fed on potato foliage dipped with dsEcR in a laboratory bioassay. Around 85% of the HvEcR RNAi larvae remained as prepupae or became abnormal pupae, and failed to emerge into adults. Ingestion of dsEcR‐immersed foliage by the 3rd‐instar larvae effectuated a comparable RNAi response and brought about more severe defects: all the resultant larvae arrested development, remained as prepupae and finally died. For assay in the greenhouse, a dsEcR‐contained E. coli suspension was directly sprayed to the foliage of greenhouse‐growing potato plants and the 3rd‐ and 4th‐instar larvae were transferred to the leaves. High RNAi efficacy was obtained and identical RNAi phenotypes were observed in treated larvae. In addition, spraying dsEcR reduced leaf damage. Our results indicate a possibility of practical application of dsEcR as an environmentally friendly RNA pesticide to control H. vigintioctopunctata larvae. [ABSTRACT FROM AUTHOR]

Post-embryonic development of insects is highly dependent on ecdysteroid hormone 20-hydroxyecdysone. Halloween gene spookier ( spok, cyp307a2) has been documented to be involved in ecdysteroidogenesis in Drosophila melanogaster and Bombyx mori. We describe here the cloning and characterization of Halloween gene spookier ( Lsspok, Lscyp307a2) in the small brown planthopper Laodelphax striatellus, a hemipteran insect species. LsSPOK has three insect-conserved P450 motifs, that is, Helix-K, PERF motif and heme-binding domain. Temporal and spatial expression patterns of Lsspok were evaluated by quantitative polymerase chain reaction. Through the fouth-instar and the early fifth-instar stages, Lsspok showed two expression peaks in the second- and fifth-day fourth-instar nymphs, and two troughs in the first-day fourth and fifth instars. On day 5 of the fourth-instar nymphs, Lsspok clearly had a high transcript level in the thorax where prothoracic glands were located. Dietary introduction of double-stranded RNA of Lsspok in the nymph stage successfully knocked down the target gene, decreased expression level of ecdysone receptor ( LsEcR) gene, caused nymphal lethality and delayed development. Ingestion of 20-hydroxyecdysone in Lsspok-dsRNA-exposed nymphs did not increase Lsspok expression level, but almost completely rescued the LsEcR mRNA level and relieved the negative effects on survival and development. Thus, our data suggest that the ecdysteroidogenic pathway is conserved in insects and LsSPOK is responsible for specific steps in ecdysteroidogenesis in L. striatellus. [ABSTRACT FROM AUTHOR]

Leptinotarsa decemlineata adults exhibit a season-dependent activity. In spring, post-diapause beetles often fly a long distance from overwintering sites to potato fields. In summer and autumn, the flight ability is sharply reduced. Proline is the main energy substrate of L. decemlineata during flight and proline dehydrogenase (ProDH) catalyzes the first step in proline catabolism. Here we identified a putative LdProDH gene; it had three cDNA isoforms which shared the same 5′UTR and coding region, but differed in the lengths of 3′UTRs (515, 1 092 and 1 242 bp for isoforms-1, -2 and -3, respectively). LdProDH encoded a 616 amino acid protein that showed high sequence similarity to ProDH-like proteins from other insect species. LdProDH was expressed in the third and fourth instars larvae and adults, but not in pupae. Dietary ingestion of bacterially expressed LdProDH-dsRNA by adults significantly decreased its messenger RNA (mRNA) level, and caused an elevation of free proline content in the hemolymph. Further observation revealed that three canonical polyadenylation signals (AATAAA) were tandemly located in the 3′UTR of isoform-3. The first, second and third polyadenylation sites gave rise to isoforms-1, -2 and -3, respectively. Analysis of the genomic DNA uncovered that the three isoforms resulted from alternative polyadenylation. The mRNA level of isoform-1, which expressed at low levels in pre-diapause adults, became abundant in post-diapause beetles. It is indicated that the LdProDH expression is fine-tuned through 3′UTR to control proline catabolism for the season-dependent activity of L. decemlineata adults. [ABSTRACT FROM AUTHOR]