摘要: Insect hemocytes play important biological roles at developmental stages, metamorphosis, and innate immunity. As one of the most abundant cell types, plasmatocytes can participate in various innate immune responses, especially in encapsulation and node formation. Here, 2 molecular markers of plasmatocytes, consisting of integrin beta 2 and beta 3, were identified and used to understand the development of plasmatocytes. Plasmatocytes are widely distributed in the hematopoietic system, including circulating hemolymph and hematopoietic organs (HPOs). HPOs constantly release plasmatocytes with high proliferative activity in vitro; removal of HPOs leads to a dramatic reduction in the circulating plasmatocytes, and the remaining plasmatocytes gradually lose their ability to proliferate in vivo. Our results demonstrated that the release of plasmatocytes from HPOs is regulated by insulin-mediated signals and their downstream pathways, including PI3K/Akt and MAPK/Erk signals. The insulin/PI3K/Akt signaling pathway can significantly irritate the hematopoiesis, and its inhibitor LY294002 could inhibit the hemocytes discharged from HPOs. While the insulin/MAPK/Erk signaling pathway plays a negative regulatory role, inhibiting its activity with U0126 can markedly promote the discharge of plasmatocytes from HPOs. Our results indicate that the circulating plasmatocytes are mainly generated and discharged by HPOs. This process is co-regulated by the PI3K/Akt and MAPK/Erk signals in an antagonistic manner to adjust the dynamic balance of the hemocytes. These findings can enhance our understanding of insect hematopoiesis.

摘要: The E2F family of transcription factors is crucial for cell cycle progression and cell fate decisions. Although E2Fs have been widely studied in mammals, there have been few studies performed in insects. Here, we determined the function of E2F4 in the silkworm, Bombyx mori. We demonstrate that E2F proteins are highly conserved among species from lower animals to higher mammals. Overexpression of the BmE2F4 gene led to cell cycle arrest in the G1 phase, whereas interfering with the BmE2F4 mRNA led to accumulation of cells in the S phase. These results indicate that BmE2F4 is important in cell cycle regulation. We also demonstrate that the BmE2F4 gene is involved in DNA replication of BmN-SWU1 cells and DNA synthesis in the silk gland. Furthermore, we identified a protein called Bm14-3-3 zeta that can interact with BmE2F4 and allow it to localize in the nucleus. Overexpression of the Bm14-3-3 zeta gene led to cell cycle arrest in the G1 phase, while knocking down the gene increased the proportion of cells in S phase. These findings provide important insights into the function of E2F transcription factors and increase our understanding of their involvement in cell cycle regulation.

摘要: The biogenic amine octopamine (OA, invertebrate counterpart of noradrenaline) plays critical roles in the regulation of olfactory behavior. Historically, OA has been thought to mediate appetitive but not aversive learning in honeybees, fruit flies (Drosophila), and crickets. However, this viewpoint has recently been challenged because OA activity through a beta-adrenergic-like receptor drives both appetitive and aversive learning. Here, we explored the roles of OA neurons in olfactory learning and memory retrieval in Bactrocera dorsalis. We trained flies to associate an orange odor with a sucrose reward or to associate methyl eugenol, a male lure, with N,N-diethyl-3-methyl benzoyl amide (DEET) punishment. We then treated flies with OA receptor antagonists before appetitive or aversive conditioning and a memory retention test. Injection of OA receptor antagonist mianserin or epinastine into the abdomen of flies led to impaired of appetitive learning and memory retention with a sucrose reward, while aversive learning and memory retention with DEET punishment remained intact. Our results suggest that the OA signaling participates in appetitive but not aversive learning and memory retrieval in B. dorsalis through OA receptors.

摘要: Trehalose is the principal sugar circulating in the hemolymph of insects, and trehalose synthesis is catalyzed by trehalose-6-phosphate synthase (TPS) and trehalose-6-phosphate phosphatase (TPP). Insect TPS is a fused enzyme containing both TPS domain and TPP domain. Thus, many insects do not possess TPP genes as TPSs have replaced the function of TPPs. However, TPPs are widely distributed across the dipteran insects, while the roles they play remain largely unknown. In this study, 3 TPP genes from notorious dipteran pest Bactrocera minax (BmiTPPB, BmiTPPC1, and BmiTPPC2) were identified and characterized. The different temporal-spatial expression patterns of 3 BmiTPPs implied that they exert different functions in B. minax. Recombinant BmiTPPs were heterologously expressed in yeast cells, and all purified proteins exhibited enzymatic activities, despite the remarkable disparity in performance between BmiTPPB and BmiTPPCs. RNA interference revealed that all BmiTPPs were successfully downregulated after double-stranded RNA injection, leading to decreased trehalose content and increased glucose content. Also, suppression of BmiTPPs significantly affected expression of downstream genes and increased the mortality and malformation rate. Collectively, these results indicated that all 3 BmiTPPs in B. minax are involved in trehalose synthesis and metamorphosis. Thus, these genes could be evaluated as insecticidal targets for managing B. minax, and even for other dipteran pests.

摘要: Carotenoids are involved in many essential physiological functions and are produced from geranylgeranyl pyrophosphate through synthase, desaturase, and cyclase activities. In the pea aphid (Acyrthosiphon pisum), the duplication of carotenoid biosynthetic genes, including carotenoid synthases/cyclases (ApCscA-C) and desaturases (ApCdeA-D), through horizontal gene transfer from fungi has been detected, and ApCdeB has known dehydrogenation functions. However, whether other genes contribute to aphid carotenoid biosynthesis, and its specific regulatory pathway, remains unclear. In the current study, functional analyses of seven genes were performed using heterologous complementation and RNA interference assays. The bifunctional enzymes ApCscA-C were responsible for the synthase of phytoene, and ApCscC may also have a cyclase activity. ApCdeA, ApCdeC, and ApCdeD had diverse dehydrogenation functions. ApCdeA catalyzed the enzymatic conversion of phytoene to neurosporene (three-step product), ApCdeC catalyzed the enzymatic conversion of phytoene to zeta-carotene (two-step product), and ApCdeD catalyzed the enzymatic conversion of phytoene to lycopene (four-step product). Silencing of ApCscs reduced the expression levels of ApCdes, and silencing these carotenoid biosynthetic genes reduced the alpha-, beta-, and gamma-carotene levels, as well as the total carotenoid level. The results suggest that these genes were activated and led to carotenoid biosynthesis in the pea aphid.