Insect Biochemistry and Molecular Biology最新文献

Periplocosides, extracted from the root bark of Periploca sepium, are plant secondary compounds known to inhibit the V-ATPase enzyme in susceptible insect species, such as Mythimna separata. However, many species, including Spodoptera exigua, show resistance to these compounds. Previous studies identified the V-ATPase subunit A (VATP-A) in the midgut epithelium of M. separata as the putative target of periplocoside P (PSP), but the specific amino acids involved in this interaction remained unclear. In this study, we demonstrate the selective toxicity of PSP and its inhibition effect on V-ATPase. Molecular docking identified potential interactions between PSP and three amino acids (K85, R171, E199) in MsVATP-A, with in vitro binding assays revealing that K85 and R171 serve as the primary binding sites. Notably, sequence alignment revealed that R171 in sensitive species is substituted with K in resistant species. To investigate the functional implications of this substitution, we performed in vitro site-directed mutagenesis to exchange the corresponding amino acids between the VATP-A orthologs of M. separata and S. exigua. The R171K mutation in MsVATP-A reduced binding to PSP, while the K170R mutation in SeVATP-A enhanced it. Furthermore, in vivo genome editing in Drosophila melanogaster, a PSP-sensitive species, revealed that the R171K mutation conferred 15.78-fold resistance to PSP compared to the wild-type strain (w¹¹¹⁸). Our findings confirm the role of VATP-A as the target of PSP and elucidate the key amino acids influencing its insecticidal selectivity. This research enhances the understanding of the molecular interactions between natural compounds and insect targets, offering insights for the development of targeted pest control strategies.

Peptidoglycan recognition proteins (PGRPs) are evolutionarily conserved molecules. Their role in the immune response to invading pathogens makes them a natural target for viral defence study in a wide range of organisms. Silverleaf whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is one of the invasive insect pests and transmits begomoviruses in a circulative and persistent manner to vegetables, legumes, fibres and ornamentals. The virus entry, retention, circulation, and release process involve interactions with several proteins in B. tabaci and evade innate immunity to avoid the antiviral mechanisms. The present study investigated the role of BtPGRP in chilli leaf curl virus (ChiLCV, Begomovirus capsica) transmission by B. tabaci. Silencing of BtPGRP using double-stranded (ds) RNA led to the loss of innate immunity to ChiLCV resulting in increased virus titre in B. tabaci. dsBtPGRP was orally administered to adults of B. tabaci at a concentration of 1, 3, and 5 ug/mL. The expression of BtPGRP was downregulated up to 4.67-fold. The virus titre in B. tabaci increased 90.05 times post-exposure to dsBtPGRP at 5 μg/mL. The test plants inoculated with ChiLCV by dsBtPGRP-exposed B. tabaci expressed severe curling symptoms with a higher virus load and transmission ratio than the control. Besides, the silencing of BtPGRP also induced up to 56.67% mortality in treated B. tabaci. The active site pocket of BtPGRP was found to interact directly with the ChiLCV-CP in computational analyses. Key residues of BtPGRP, including Tyr45, Asp84, His86, Trp87, and Asn119 exhibited critical interaction with the ChiLCV-CP. To our knowledge, this is the first report on the effect of PGRP silencing on ChiLCV acquisition and transmission by B. tabaci Asia II I and its fitness.

Plasticity in animal behavior and physiology is largely due to modulatory and regulatory signaling with neuropeptides and peptide hormones (collectively abbreviated NPHs). The NPHs constitute a very large and versatile group of signaling substances that partake at different regulatory levels in most daily activities of an organism. This review summarizes key principles in NPH actions in the brain and in interorgan signaling, with focus on Drosophila. NPHs are produced by neurons, neurosecretory cells (NSCs) and other endocrine cells in NPH-specific and stereotypic patterns. Most of the NPHs have multiple (pleiotropic) functions and target several different neuronal circuits and/or peripheral tissues. Such divergent NPH signaling ensures orchestration of behavior and physiology in state-dependent manners. Conversely, many neurons, circuits, NSCs, or other cells, are targeted by multiple NPHs. This convergent signaling commonly conveys various signals reporting changes in the external and internal environment to central neurons/circuits. As an example of wider functional convergence, 26 different Drosophila NPHs act at many different levels to regulate food search and feeding. Convergence is also seen in hormonal regulation of peripheral functions. For instance, multiple NPHs target renal tubules to ensure osmotic homeostasis. Interestingly, several of the same osmoregulatory NPHs also regulate feeding, metabolism and stress. However, for some NPHs the cellular distribution and functions suggests multiple unrelated functions that are restricted to specific circuits. Thus, NPH signaling follows distinct patterns for each specific NPH, but taken together they form overlapping networks that modulate behavior and physiology.

Normal gastrointestinal (GI) motility, including defecation, is crucial for nutrient absorption, energy balance, and overall health in species ranging from insects to humans. Disruptions in GI motility can lead to conditions like constipation or severe diseases. Mechanosensors, including TRP channels and Piezo, are known to play key roles in regulating gut physiology in Drosophila melanogaster, but their precise involvement in defecation is not fully understood. Additionally, neuropeptides like DH44 have been implicated in gut regulation. This study explores the roles of Trpγ, Diuretic hormone 44 Receptor 2 (DH44R2), and Piezo in controlling feeding amount, gut motility, and defecation using genetic mutants and RNAi techniques. Mutants for these genes exhibited increased excreta production and size, whereas Dh44 and Dh44R1 mutants had a reduced number of excreta, but with increased size. Co-expression and rescue experiments further confirmed the critical roles of these genes in the same gut cells. The findings reveal that local gut-specific mechanisms are the primary drivers of defecation. The results highlight the collaboration between Trpγ, Piezo, and DH44R2 in regulating gut motility and defecation. By uncovering how these mechanosensory proteins and cells work together, this research may offer insights into human GI disorders like Irritable Bowel Syndrome (IBS) and Hirschsprung's disease, shedding light on the complex regulatory network underlying defecation.