Archives of Insect Biochemistry and Physiology最新文献

The zona pellucida domain protein piopio (Pio) was only reported to mediate the adhesion of the apical epithelial surface and the overlying apical extracellular matrix in Drosophila melanogaster, but the developmental roles of Pio were poorly understood in insects. To address this issue, we comprehensively analyzed the function of Pio in Tribolium castaneum. Phylogenetic analysis indicated that pio exhibited one-to-one orthologous relationship among insects. T. castaneum pio had a 1236-bp ORF and contained eight exons. During development pio was abundantly expressed from larva to adult and lowly expressed at the late stage of embryo and adult, while it had more transcripts in the head, epidermis, and gut but fewer in the fat body of late-stage larvae. Knockdown of pio inhibited the pupation, eclosion, and reproduction of T. castaneum. The expression of vitellogenin 1 (Vg1), Vg2, and Vg receptor (VgR) largely decreased in pio-silenced female adults. Silencing pio increased the 20-hydroxyecdysone titer by upregulating phm and spo expression but decreased the juvenile hormone (JH) titer through downregulating JHAMT3 and promoting JHE, JHEH-r4, and JHDK transcription. These results suggested that Pio might regulate the metamorphosis and reproduction via modulating the ecdysone and JH metabolism in T. castaneum. This study found the novel roles of pio in insect metamorphosis and reproduction, and provided the new insights for analyzing other zona pellucida proteins functions in insects.

Zeugodacus cucurbitae (Coquillett) is an important fruit and vegetable pest, especially in high-temperature seasons. In our previous research, we developed a temperature-sensitive sustained-release attractant for Z. cucurbitae, that not only can control the release rate of cuelure according to the temperature change, but also shows an excellent trapping effect on Z. cucurbitae. To further enhance the killing effect of the temperature-sensitive attractant on Z. cucurbitae, this study proposed using it in combination with an insecticide to prepare a temperature-sensitive insecticide for Z. cucurbitae. Based on the controlled release technology of pesticides, a temperature-sensitive Z. cucurbitae insecticide was developed by using PNIPAM gel as a temperature-sensitive switch to carry both cuelure and insecticide at the same time. In addition, the lethal effect of different pesticides on Z. cucurbitae were tested by indoor toxicity test, and the best pesticide combination was screened out. The temperature-sensitive insecticide prepared in this study not only had excellent thermal response and controlled release ability, but also enhanced its toxicological effects on Z. cucurbitae because it contained insecticides. Among them, combining thiamethoxam and clothianidin with the temperature-sensitive attractants was the most effective, and their lethality reached more than 97% against Z. cucurbitae. This study is not only of great practical significance for the monitoring and controlling Z. cucurbitae, but also provides theoretical basis and reference value for the combination of temperature-sensitive attractant and insecticide.

The vitellogenin receptor (VgR) is essential for the uptake and transport of the yolk precursor, vitellogenin (Vg). Vg is synthesized in the fat body, released in the hemolymph, and absorbed in the ovaries, via receptor-mediated endocytosis. Besides its important role in the reproductive pathway, Vg occurs in nonreproductive worker honey bee, suggesting its participation in other pathways. The objective was to verify if the VgR occurs in the hypopharyngeal glands of Apis mellifera workers and how Vg is internalized by these cells. VgR occurrence in the hypopharyngeal glands was evaluated by qPCR analyses of VgR and immunohistochemistry in workers with different tasks. The VgR gene is expressed in the hypopharyngeal glands of workers with higher transcript levels in nurse honey bees. VgR is more expressed in 11-day-old workers from queenright colonies, compared to orphan ones. Nurse workers with developed hypopharyngeal glands present higher VgR transcripts than those with poorly developed glands. The immunohistochemistry results showed the co-localization of Vg, VgR and clathrin (protein that plays a major role in the formation of coated vesicles in endocytosis) in the hypopharyngeal glands, suggesting receptor-mediated endocytosis. The results demonstrate that VgR performs the transport of Vg to the hypopharyngeal glands, supporting the Ovary Ground Plan Hypothesis and contributing to the understanding of the role of this gland in the social context of honey bees.

Studies on antiaging remedies in insect models sometimes show discrepancies in results. These discrepancies could be explained by different responses of short- and long-lived strains on the antiaging remedies. The purpose of the study was to test whether life-prolonging effects of alpha-ketoglutarate (AKG), observed in nematodes and fruit flies, would be reproduced in long-lived Drosophila melanogaster flies. Lifespan was assayed in flies kept in demographic cages. Fecundity, proportion of flies capable of negative geotaxis, starvation resistance, time of heat coma onset, levels of triacyglycerols, body glucose, glycogen, activities of glutamate dehydrogenase, catalase, glutathione-S-transferase, hexokinase, phosphofructokinase, pyruvate kinase, lactate, and glutamate dehydrogenases were assessed. Dietary AKG did not affect fly lifespan on the diet with 5% yeast and 5% sucrose (5Y:5S) and on the diet with 9% yeast and 1% sucrose (9Y:1S), but increased lifespan on the low-protein diet (1Y:9S). Twenty-five-day-old female flies fed a 5Y:5S diet with 10 mM AKG for 3 weeks, did not differ from the control group (without AKG) in climbing activity, resistance to heat stress, and starvation. The levels of glucose and glycogen were unaffected but the levels of triacylglycerols were lower in AKG-fed female flies. No differences in activities of glycolytic enzymes, NADPH-producing enzymes, glutamate dehydrogenase, oxygen consumption, and levels of oxidative stress markers were observed between the control and AKG-fed flies. However, AKG-fed flies had lower activities of catalase and glutathione-S-transferase. These results suggest that potential antiaging remedies, such as AKG, may not extend lifespan in long-living organisms despite influencing several metabolic parameters.

We detected enzymatic activity that generates 20-nucleotide (nt) RNA from double-stranded RNAs (dsRNAs) in crude extracts prepared from various silkworm (Bombyx mori) organs. The result using knocked-down cultured cells indicated that this dicing activity originated from B. mori Dicer-2 (BmDcr2). Biochemical analyses revealed that BmDcr2 preferentially cleaves 5′-phosphorylated dsRNAs at the 20-nt site—counted from the 5′-phosphorylated end—and required ATP and magnesium ions for the dicing reaction. This is the first report of the biochemical characterization of Dicer-2 in lepidopteran insects. This enzymatic property of BmDcr2 in vitro is consistent with the in vivo small interfering RNA profile in virus-infected silkworm cells.

More and more evidence shows that small noncoding RNAs (ncRNAs) play diverse roles in development, stress response and other cellular processes, but functional study of intermediate-size ncRNAs is still rare. Here, the expression profile of 16 intermediate-size ncRNAs in ovary and testis of silkworm Bombyx mori were analyzed. Twelve ncRNAs, including 5 small nucleolar RNAs (snoRNAs) and 7 unclassified ncRNAs, accumulated more in the testis than in the ovary of silkworm, especially Bm-163, Bm-51 and Bm-68. Four ncRNAs (including three orphan snoRNAs and one unclassified ncRNA) had higher expression level in the ovary than in the testis, especially Bm-86. Overexpression of the testis-enriched snoRNA Bm-68 in the female led to the accumulation of male-specific isoform of doublesex (Bmdsx^M) and increased the expression ratio of Bmdsx^M: Bmdsx^F. While overexpression of ovary-enriched snoRNA Bm-86 in the male decreased the expression ratio of Bmdsx^M: Bmdsx^F, indicating the roles of the two snoRNAs played in the alternative splicing of Bmdsx of silkworm, which will provide new clues for the functional study of snoRNAs in insects.

The insect cuticle plays a key role in maintaining the insect's physiological function and behavior. Herein, the yellow-y protein is required to produce black melanin, and is expressed in a pattern that correlates with the distribution of this pigment. However, yellow-y can also have other functions, for instance, in insect behavior, but not much is known. In this study, we have studied the yellow-y gene in one important model and pest species, namely the German cockroach (Blattella germanica), which is to our knowledge the first time reported. In essence, we identified the yellow-y gene (BgY-y) and characterized its function by using RNA interference (RNAi). Silencing of BgY-y gene led to different developmental abnormalities (body weight and wings) in both genders. Specifically, there was an abundant decrease in melanin, turning the body color in pale yellow and the cuticle softer and more transparent. Interestingly, we also observed that the knockdown of BgY-y impaired the male cockroaches to display a weaker response to female-emitted contact sex pheromones, and also that the oviposition ability was weakened in the RNAi females. This study comprehensively analyzed the biological functions of the yellow-y gene in German cockroaches from the perspectives of development, body color, courtship behavior and oviposition, and as a consequence, this may opens new avenues to explore it as a novel pest control gene.

The efficiency of RNA interference (RNAi) has always limited the research on the phenotype innovation of Lepidoptera insects. Previous studies have found that double-stranded RNA-degrading enzyme (dsRNase) is an important factor in RNAi efficiency, but there have been no relevant reports in butterflies (Papilionoidea). Papilio xuthus is one of the important models in butterflies with an extensive experimental application value. To explore the effect of dsRNase in the RNAi efficiency on butterflies, six dsRNase genes (PxdsRNase 1–6) were identified in P. xuthus genome, and their dsRNA-degrading activities were subsequently detected by ex vivo assays. The result shows that the dsRNA-degrading ability of gut content (<1 h) was higher than hemolymph content (>12 h). We then investigated the expression patterns of these PxdsRNase genes during different tissues and developmental stages, and related RNAi experiments were carried out. Our results show that different PxdsRNase genes had different expression levels at different developmental stages and tissues. The expression of PxdsRNase2, PxdsRNase3, and PxdsRNase6 were upregulated significantly through dsGFP injection, and PxdsRNase genes can be silenced effectively by injecting their corresponding dsRNA. RNAi-of-RNAi studies with PxEbony, which acts as a reporter gene, observed that silencing PxdsRNase genes can increase RNAi efficiency significantly. These results confirm that silencing dsRNase genes can improve RNAi efficiency in P. xuthus significantly, providing a reference for the functional study of insects such as butterflies with low RNAi efficiency.

In insects, the expression of 20E response genes that initiate metamorphosis is triggered by a pulse of 20-hydroxyecdysone (20E). The 20E pulse is generated through two processes: synthesis, which increases its level, and inactivation, which decreases its titer. CYP18A1 functions as an ecdysteroid 26-hydroxylase and plays a role in 20E removal in several representative insects. However, applying 20E degradation activity of CYP18A1 to other insects remains a significant challenge. In this study, we discovered high levels of Hvcyp18a1 during the larval and late pupal stages, particularly in the larval epidermis and fat body of Henosepilachna vigintioctopunctata, a damaging Coleopteran pest of potatoes. RNA interference (RNAi) targeting Hvcyp18a1 disrupted the pupation. Approximately 75% of the Hvcyp18a1 RNAi larvae experienced developmental arrest and remained as stunted prepupae. Subsequently, they gradually turned black and eventually died. Among the Hvcyp18a1-depleted animals that successfully pupated, around half became malformed pupae with swollen elytra and hindwings. The emerged adults from these deformed pupae appeared misshapen, with shriveled elytra and hindwings, and were wrapped in the pupal exuviae. Furthermore, RNAi of Hvcyp18a1 increased the expression of a 20E receptor gene (HvEcR) and four 20E response transcripts (HvE75, HvHR3, HvBrC, and HvαFTZ-F1), while decreased the transcription of HvβFTZ-F1. Our findings confirm the vital role of CYP18A1 in the pupation, potentially involved in the degradation of 20E in H. vigintioctopunctata.

Insect trehalases have been identified as promising new targets for pest control. These key enzymes are involved in trehalose hydrolysis and plays an important role in insect growth and development. In this contribution, plant and microbial compounds, namely validamycin A, amygdalin, and phloridzin, were evaluated for their effect, through trehalase inhibition, on Acyrthosiphon pisum aphid. The latter is part of the Aphididae family, main pests as phytovirus vectors and being very harmful for crops. Validamycin A was confirmed as an excellent trehalase inhibitor with an half maximal inhibitory concentration and inhibitor constant of 2.2 × 10⁻⁷ and 5 × 10⁻⁸M, respectively, with a mortality rate of ~80% on a A. pisum population. Unlike validamycin A, the insect lethal efficacy of amygdalin and phloridzin did not correspond to their trehalase inhibition, probably due to their hydrolysis by insect β-glucosidases. Our docking studies showed that none of the three compounds can bind to the trehalase active site, unlike their hydrolyzed counterparts, that is, validoxylamine A, phloretin, and prunasin. Validoxylamine A would be by far the best trehalase binder, followed by phloretin and prunasin.