关键词: 褐飞虱, IIS/TOR通路, AMPK, ROS, 蜕皮激素, 保幼激素

Abstract: 【Aim】 Insects perceive external nutritional status, and nutritional signals in vivo are transmitted through many signal pathways to regulate insect growth and reproduction. This study aims to tentatively explore the molecular mechanism of nutritional regulation on the growth and reproduction of the rice brown planthopper, Nilaparvata lugens. 【Methods】 The day-2 3rd instar nymphs of N. lugens were fed to adults under different nutrient conditions ［fed with 100% artificial diet (pure artificial diet D-97, the control), 50% artificial diet and 25% artificial diet, respectively］, and the body weight, developmental duration, survival rate and number of mature eggs per ovary were counted. Then, the relative expression levels of IIS, TOR and AMPK signaling pathway related genes (InR1, InR2, AKT, FoxO, TOR, S6K, 4EBP, AMPKα, AMPKβ and AMPKγ) in different tissues (ovary, body fat and other tissues) of the 2-day-old adults were detected by quantitative PCR, and the phosphorylation levels of Akt, FoxO and AMPK in the ovary and other tissues of the 6-day-old adults were detected by Western blot. Meanwhile, the ROS levels in different tissues of the 6-day-old adults and the titers of juvenile hormone (JH) and 20-hydroxyecdysone (20E) in N. lugens at different developmental stages were also detected. 【Results】 Compared with the control fed with 100% artificial diet, the artificial diet of lower concentrations resulted in a significant decrease in body weight from the day-2 5th instar nymph to adult, shortened developmental duration from day-2 3rd instar nymphs to adult, an increased mortality, and a significant decrease in the number of mature eggs per ovary of N. lugens. The expression levels of IIS, TOR and AMPK signaling pathway related genes InR2, TOR, 4EBP and AMPKα in the ovary, body fat and other tissues, AKT, S6K and AMPKγ in the fat body and other tissues, and InR1, FoxO and AMPKβ in the other tissues of the 2-day-old adults fed with the artificial diet of lower concentrations decreased significantly as compared to those in the control, while those of InR1, AKT, FoxO, and AMPKγ  in the ovary were relatively stable. The phosphorylation levels of AKT, FoxO, and AMPK in the ovary and other tissues of the 6-day-old adults fed with the artificial diet of lower concentrations were significantly increased as compared with those of the control. With the decrease of nutrient concentration in the artificial diet, the ROS levels in different tissues of the 6-day-old adults increased significantly as compared to that in the control. The JH titers in the day-2 4th instar nymphs under different nutrient conditions showed no significant difference, while the JH titers in the day-2 5th instar nymphs and 2-day-old adults under low nutrient conditions were significantly decreased and increased, respectively, as compared to those in the control. Low nutrient conditions resulted in a significant increase in 20E titer both in nymphs and adults. 【Conclusion】 Under conditions of nutrient deficiency, the expression levels of key genes in the nutritional signal transduction pathways including IIS, TOR and APMK pathways in N. lugens decrease, while the ROS level significantly increases, and the biosynthesis of JH and 20E is affected by regulating the phosphorylation levels of AKT, FoxO and AMPK.

Key words: Nilaparvata lugens, IIS/TOR pathway, AMPK, ROS, 20-hydroxyecdysone, juvenile hormone