Combined Analysis of Metabolomics and Biochemical Changes Reveals the Nutritional and Functional Characteristics of Red Palm Weevil Rhynchophus ferrugineus (Coleoptera: Curculionidae) Larvae at Different Developmental Stages.

In this study, the changes in the conventional nutrient and mineral compositions as well as the metabolomics characteristics of the red palm weevil (RPW) Rhynchophus ferrugineus Olivier (Curculionidae: Coleoptera) larvae at early (EL), middle (ML) and old (OL) developmental stages were investigated. Results showed that the EL and ML had the highest content of protein (53.87 g/100 g dw) and fat (67.95 g/100 g), respectively, and three kinds of RPW larvae were all found to be rich in unsaturated fatty acids (52.17-53.12%), potassium (5707.12-15,865.04 mg/kg) and phosphorus (2123.87-7728.31 mg/kg). In addition, their protein contained 17 amino acids with the largest proportion of glutamate. A total of 424 metabolites mainly including lipids and lipid-like molecules, organic acids and their derivatives, organic heterocycle compounds, alkaloids and their derivatives, etc. were identified in the RPW larvae. There was a significant enrichment in the ABC transport, citrate cycle (TCA cycle), aminoacyl-tRNA biosynthesis, and mTOR signaling pathways as the larvae grow according to the analysis results of the metabolic pathways of differential metabolites. The water extract of EL exhibited relatively higher hydroxyl, 2,2-diphenyl-1-pyrroline hydrochloride (DPPH) and 2,2'-azobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical-scavenging ability with the EC50 values of 1.12 mg/mL, 11.23 mg/mL, and 2.52 mg/mL, respectively. These results contribute to a better understanding of the compositional changes of the RPW larvae during its life cycle and provide a theoretical grounding for its deep processing and high-value utilization.

Exploring the functional profiles of odorant binding proteins crucial for sensing key odorants in the new leaves of coconut palms in Rhynchophorus ferrugineus.

The red palm weevil (RPW), Rhynchophorus ferrugineus (Curculionidae: Coleoptera) is a highly destructive global pest of coconut trees, with a preference for laying its eggs on new leaves. Females can identify where to lay eggs by using their sense of smell to detect specific odorants found in new leaves. In this study, we focused on the two odorants commonly found in new leaves by GC-MS: trans, trans-2,4-nonadienal and trans-2-nonenal. Our behavioral assays demonstrated a significant attraction of females to both of these odorants, with their electrophysiological responses being dose-dependent. Furthermore, we examined the expression patterns induced by these odorants in eleven RferOBP genes. Among them, RferOBP3 and RferOBP1768 exhibited the most significant and simultaneous upregulation. To further understand the role of these two genes, we conducted experiments with females injected with OBP-dsRNA. This resulted in a significant decrease in the expression of RferOBP3 and RferOBP1768, as well as impaired the perception of the two odorants. A fluorescence competitive binding assay also showed that both RferOBPs strongly bound to the odorants. Additionally, sequence analysis revealed that these two RferOBPs belong to the Minus-C family and possess four conserved cysteines. Molecular docking simulations showed strong interactions between these two RferOBPs and the odorant molecules. Overall, our findings highlight the crucial role of RferOBP3 and RferOBP1768 in the olfactory perception of the key odorants in coconut palm new leaves. This knowledge significantly improves our understanding of how RPW females locate sites for oviposition and lays the foundation for future research on the development of environmentally friendly pest attractants.

Virulence of entomopathogenic bacteria Serratia marcescens against the red palm weevil, Rhynchophorus ferrugineus (Olivier).

Background: The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), is an important quarantine pest, which has caused serious economic losses in various palm species, such as coconut, oil palm and date palm. Finding effective biocontrol resources is important for the control of this pest and the protection of palm crops. Methods: A pathogenic strain HJ-01 was isolated from infected and dead pupa of Tenebrio molitor using tissue separation method. The HJ-01 strain was streak cultured and purified, and its morphological, physiological, biochemical characteristics, and 16S rDNA homology were identified after conducting a pathogenicity test on RPW larvae. Results: Strain HJ-01 exhibited remarkable pathogenicity against RPW larvae. Under the concentration of HJ-01 suspension was 1.0 × 108 cfu/mL, the mortality rate of RPW reached 82.22%, and the half-lethal time (LT50) was 4.72 days. RPW larvae infected with strain HJ-01 showed reduced movement, decreased appetite, and eventual death. As the treatment progresses, the larvae's bodies turned red, became soft, and started to rot, resulting in the discharge of liquid. HJ-01 demonstrated the ability to produce scarlet pigment after 24 h of culture on a basic medium. Colonies of HJ-01 appeared convex, bright red, moist, and viscous, opaque in the center, irregular at the edges, and emitted an unpleasant odor. Under microscopic observation, the cells of HJ-01 appeared as short rod-shaped and flagellate, with a size ranging from (1.2-1.8) µm × (1.0-1.2) µm. Genomic DNA extraction was performed on the strain, and the 16S rDNA sequence was amplified, yielding a sequence length of 1445 bp. The sequence of strain HJ-01 displayed a 99.72% similarity to that of Serratia marcescens. Phylogenetic tree analysis further confirmed that strain HJ-01 belonged to S. marcescens. Therefore, the strain HJ-01 has a very good lethal effect on RPW larvae, and it may be used as an effective bacterium for the control of RPW.

Preliminary study on biology and feeding capacity of Chelisoches morio (Fabricius) (Dermaptera:Chelisochidae) on Tirathaba rufivena (Walker).

BACKGROUND: Chelisoches morio (Fabricius) (Dermaptera:Chelisochidae) is an important predator of Tirathaba rufivena (Walker) (Lepidoptera:Pyralidae). For better use of the natural enemy, a biological study on C. morio was conducted, particularly its developmental duration, survival, fecundity and sex ratio. And the feeding capacity of C. morio against T. rufivena was also studied under laboratory conditions. RESULTS: The biological study on C. morio was revealed that female adults usually lay eggs in egg masses. The number of eggs per female averaged 140.17 eggs, and the incubation period was 7.50 days. The duration of nymphal development included four instars. The immature period was 83.95 days. The longevity of males and females was 58.60 and 93.55 days, respectively. The results from the study on the feeding capacity of C. morio using T. rufivena as food revealed that C. morio adults could consume 11.08, 7.87, 7.09, 6.82 and 5.89 first-to-fifth-instar T. rufivena larvae, respectively. CONCLUSIONS: C. morio showed a huge amount of predation on this pest at all larval stages, implying a significant potential for the use of C. morio in controlling T. rufivena.

The mitochondria-mediate apoptosis of Lepidopteran cells induced by azadirachtin.

Mitochondria have been shown to play an important role in apoptosis using mammalian cell lines. However, this seems not to be the case in Drosophila, an insect model organism; thus more in-depth studies of insect cell apoptosis are necessary. In the present study, mitochondrial involvement during azadirachtin- and camptothecin-induced apoptosis in Spodoptera frugiperda Sf9 cells (isolated from Spodoptera frugiperda pupal ovarian tissue) was investigated. The results showed that both azadirachtin and camptothecin could induce apoptosis in Sf9 cells. Reactive oxygen species (ROS) generation, activation of mitochondrial permeability transition pores (MPTPs) and loss of mitochondrial membrane potential (MMP) were observed very early during apoptosis and were followed subsequently by the release of cytochrome-c from the mitochondria. Furthermore, the results also revealed that the opening of MPTPs and the loss of MMP induced by azadirachtin could be significantly inhibited by the permeability transition pore (PTP) inhibitor cyclosporin A (CsA), which was used to identify the key role of mitochondria in the apoptosis of Sf9 cells. However, in camptothecin-treated Sf9 cells, CsA could not suppress the opening of MPTPs and the loss of MMP when apoptosis was induced. The data from caspase-3 and caspase-9 activity assays and detection of apoptosis by morphological observation and flow cytometry also uncovered the different effect of CsA on the two botanical apoptosis inducers. Although different mechanisms of apoptosis induction exist, our study revealed that mitochondria play a crucial role in insect cell line apoptosis.

Four botanical extracts are toxic to the hispine beetle, Brontispa longissima, in laboratory and semi-field trials.

The potential of botanical extracts such as Celosia argenea L. (Caryophyllales: Amaranthaceae), Ricinus communis L. (Malpighiales: Euphorbiaceae), Mikania micrantha Humboldt, Bonpland & Kunth (Astrales: Asteraceae), and Catharanthus roseus (L.) G. Don (Gentianales: Apocynaceae) for the control of Brontispa longissima Gestro was evaluated in a bioassay and semi-field trial. Dose-response bioassay showed no significant difference in oral-toxicity among the extracts of C. argenea, M. micrantha, and C. roseus to larvae and adult of B. longissima. All extracts tested decreased the hatchability of B. longissima eggs. In particular, the extract of M. micrantha showed higher activity than others at the concentration of 5 mg/mL. In an antifeedant bioassay, the extract of C. argenea showed higher activity against the 1(st) larvae than that of other extracts (AF50 0.03 mg/mL), and C. roseus showed higher antifeedant activity to the 2(nd) to 5(th) larvae and adult of B. longissima (AF50 0.34, 0.33, 0.11, 0.43, and 0.20 mg/mL, respectively). The semi-field trial indicated that all extracts used in this study might reduce the pest population. Extracts of C. argenea and M. micrantha showed higher activities than that of C. roseus and R communis, and the decrease in population was 75.56% and 80.00% (without Abbott's correction) after seven days of treatment, respectively, at a concentration of 20 mg/mL. Therefore, these active botanical extracts may possess potential for use in control of B. longissima.