Insulin receptors play key roles in growth, development, and polymorphism in insects. Here, we report two insulin receptor genes (AcInR1 and AcInR2) from the brown citrus aphid, Aphis (Toxoptera) citricidus. Transcriptional analyses showed that AcInR1 increased during the nymph–adult transition in alate aphids, while AcInR2 had the highest expression level in second instar nymphs. AcInR1 is important in aphid development from fourth instar nymphs to adults as verified by dsRNA feeding mediated RNAi. The silencing of AcInR1 or/and AcInR2 produced a variety of phenotypes including adults with normal wings, malformed wings, under-developed wings, and aphids failing to develop beyond the nymphal stages. Silencing of AcInR1 or AcInR2 alone, and co-silencing of both genes, resulted in 73% or 60%, and 87% of aphids with problems in the transition from nymph to normal adult. The co-silencing of AcInR1 and AcInR2 resulted in 62% dead nymphs, but no mortality occurred by silencing of AcInR1 or AcInR2 alone. Phenotypes of adults in the dsInR1 and dsInR2 were similar. The results demonstrate that AcInR1 and AcInR2 are essential for successful nymph–adult transition in alate aphids and show that RNAi methods may be useful for the management of this pest.

Juvenile hormone (JH) plays an important role in regulating growth, development, and reproduction of insects. Three key enzymes, namely, JH esterase (JHE), JH epoxide hydrolase (JHEH), and JH diol kinase (JHDK), are involved in JH degradation. In this study, we identified the full-length cDNAs of the 3 genes BdJHEH2, BdJHEH3, and BdJHDK encoding JHEH and JHDK from the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). We used quantitative real-time polymerase chain reaction to investigate mRNA expression profiles of these 3 genes in various development stages and tissues, and in response to both 20-hydroxyecdysone (20E) and starvation. Both BdJHEH2 and BdJHDK were highly expressed during the larval—pupal transition, whereas BdJHEH3 was mainly expressed in the early 3rd instars. All 3 genes were highly expressed in 7-d-old and 10-d-old adults, but exhibited sex-specific expression patterns. BdJHEH2 was highly expressed in fat body, whereas BdJHEH3 and BdJHDK were most abundant in Malpighian tubules. In response to 20E exposure, the 3 genes were significantly up-regulated at various time points compared with the control. However, the transcript levels of BdJHDK decreased significantly during the initial exposure to 20E. After starvation treatment, expression of BdJHEH2 and BdJHEH3 significantly decreased, whereas BdJHDK was up-regulated. No significant change was observed after feeding resumption. These 3 genes have distinct roles in regulating growth and development of B. dorsalis. La hormona juvenil (JH) juega un papel importante en la regulación de crecimiento, el desarrollo y la reproducción de los insectos. Tres enzimas clave, JH esterasa (JHE), JH epóxido hidrolasa (JHEH), y JH diol quinasa (JHDK), están implicadas en la degradación de JH. En este estudio, hemos identificado los ADNc de longitud completa de los 3 genes BdJHEH2, BdJHEH3 y BdJHDK que codifican JHEH y JHDK de la mosca oriental de la fruta, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). Se utilizó PCR cuantitativa en tiempo real para investigar los perfiles de expresión de mRNA de estos 3 genes en diferentes estadios de desarrollo y tejidos, y en respuesta a tanto 20-hidroxiecdisona (20E) y la inanicion. Tanto BdJHEH2 y BdJHDK fueron altamente expresado durante la transición larval-pupal, mientras que BdJHEH3 se expresó principalmente en el 3er estadio temprano. Todos los 3 genes fueron altamente expresado en los adultos de 7 días de edad y de 10 días de edad, pero exhiben patrones de expresión específicos al sexo. BdJHEH2 fue altamente expresado en la grasa corporal, mientras que BdJHEH3 y BdJHDK fueron más abundantes en los túbulos de Malpighi. En respuesta a la exposición 20E, los 3 genes fueron significativamente hasta reguladas en varios puntos de tiempo en comparación con el control. Sin embargo, los niveles de transcripción de BdJHDK disminuyeron significativamente durante la exposición inicial a 20E. Después del tratamiento de inanicion, la expresión de BdJHEH2 y BdJHEH3 disminuyó significativamente, mientras que BdJHDK su regulacion aumento. No se observó ningún cambio significativo después de la reanudación de la alimentación. Estos 3 genes tienen funciones distintas en la regulación del crecimiento y el desarrollo de B. dorsalis.