Proteo-Transcriptomic Characterization of Sirex nitobei (Hymenoptera: Siricidae) Venom

Antioxidant Activity and Mechanism of Action of Amwaprin: A Protein in Honeybee (Apis mellifera) Venom

Bee venom contains several bioactive components, including enzymatic and non-enzymatic proteins. There is increasing interest in the bioactive components of bee venom since they have exhibited various pharmacological effects. Recently, Apis mellifera waprin (Amwaprin) was identified as a novel protein in Apis mellifera (honeybee) venom and characterized as an antimicrobial agent. Herein, the novel biological function of Amwaprin as an antioxidant is described. In addition, the antioxidant effects of Amwaprin in mammalian cells were investigated. Amwaprin inhibited the growth of, oxidative stress-induced cytotoxicity, and inflammatory response in mammalian NIH-3T3 cells. Amwaprin decreased caspase-3 activity during oxidative stress and exhibited protective activity against oxidative stress-induced cell apoptosis in NIH-3T3 and insect Sf9 cells. The mechanism underlying the cell protective effect of Amwaprin against oxidative stress is due to its direct binding to the cell membrane. Furthermore, Amwaprin demonstrated radical-scavenging activity and protected against oxidative DNA damage. These results suggest that the antioxidant capacity of Amwaprin is attributed to the synergistic effects of its radical-scavenging action and cell shielding, indicating its novel role as an antioxidant agent.

Identification of waprin and its microbicidal activity: A novel protein component of honeybee (Apis mellifera) venom

Bee venom is a rich source of biologically and pharmacologically active proteins. Waprin is a protein component of venoms; however, waprin has yet to be identified in bee venom. Moreover, the biological functions of waprin in venoms remain poorly characterized. Thus, in this study, we have identified and characterized waprin: a novel protein component from the venom of honeybees (Apis mellifera). The waprin in A. mellifera venom (Amwaprin) was found to consist of an 80-amino acid mature peptide, in which the whey acidic protein domain contains four conserved disulfide bonds. We discovered the presence of the Amwaprin protein in secreted venom by using an antibody against recombinant Amwaprin produced in baculovirus-infected insect cells. Recombinant Amwaprin exhibited inhibitory activity against microbial serine proteases and elastases but not thrombin or plasmin. It recognized carbohydrates in the microbial cell wall molecules and bound to the live microbial surfaces. The binding action of Amwaprin produced its microbicidal activity by inducing structural damage to bacterial and fungal cell walls. In addition, recombinant Amwaprin is heat-stable and contains no hemolytic activity. These findings demonstrate that Amwaprin acts as a microbicidal and anti-elastolytic agent.

Functional and Proteomic Insights into Aculeata Venoms

Aculeate hymenopterans use their venom for a variety of different purposes. The venom of solitary aculeates paralyze and preserve prey without killing it, whereas social aculeates utilize their venom in defence of their colony. These distinct applications of venom suggest that its components and their functions are also likely to differ. This study investigates a range of solitary and social species across Aculeata. We combined electrophoretic, mass spectrometric, and transcriptomic techniques to characterize the compositions of venoms from an incredibly diverse taxon. In addition, in vitro assays shed light on their biological activities. Although there were many common components identified in the venoms of species with different social behavior, there were also significant variations in the presence and activity of enzymes such as phospholipase A2s and serine proteases and the cytotoxicity of the venoms. Social aculeate venom showed higher presence of peptides that cause damage and pain in victims. The venom-gland transcriptome from the European honeybee (Apis mellifera) contained highly conserved toxins which match those identified by previous investigations. In contrast, venoms from less-studied taxa returned limited results from our proteomic databases, suggesting that they contain unique toxins.

Full-Length Transcriptome Sequencing-Based Analysis of Pinus sylvestris var. mongolica in Response to Sirex noctilio Venom

Simple Summary

Sirex noctilio, as a devastating international forestry quarantine pest whose venom can cause a series of physiological changes in the host plants, such as needle wilting, yellowing, decreased transpiration rate and increased respiration rate, etc. In this study, a full-length reference transcript of Pinus sylvestris var. mongolica was constructed by combining second- and third-generation transcriptome sequencing technologies. We also identified the specific expression genes and transcription factors of P. sylvestris var. mongolica under S. noctilio venom and wounding stress. S. noctilio venom mainly induced the expression of genes related to ROS, GAPDH and GPX, and mechanical damage mainly induced the photosynthesis−related genes. The results provide a better understanding of the molecular regulation of pine trees in response to S. noctilio venom.

Abstract

Sirex noctilio is a major international quarantine pest that recently emerged in northeast China to specifically invade conifers. During female oviposition, venom is injected into the host together with its symbiotic fungus to alter the normal Pinus physiology and weaken or even kill the tree. In China, the Mongolian pine (Pinus sylvestris var. mongolica), an important wind-proof and sand-fixing species, is the unique host of S. noctilio. To explore the interplay between S. noctilio venom and Mongolian pine, we performed a transcriptome comparative analysis of a 10-year-old Mongolian pine after wounding and inoculation with S. noctilio venom. The analysis was performed at 12 h, 24 h and 72 h. PacBio ISO-seq was used and integrated with RNA-seq to construct an accurate full-length transcriptomic database. We obtained 52,963 high-precision unigenes, consisting of 48,654 (91.86%) unigenes that were BLASTed to known sequences in the public database and 4309 unigenes without any annotation information, which were presumed to be new genes. The number of differentially expressed genes (DEGs) increased with the treatment time, and the DEGs were most abundant at 72 h. A total of 706 inoculation-specific DEGs (475 upregulated and 231 downregulated) and 387 wounding-specific DEGs (183 upregulated and 204 downregulated) were identified compared with the control. Under venom stress, we identified 6 DEGs associated with reactive oxygen species (ROS) and 20 resistance genes in Mongolian pine. Overall, 52 transcription factors (TFs) were found under venom stress, 45 of which belonged to the AP2/ERF TF family and were upregulated. A total of 13 genes related to the photosystem, 3 genes related photo-regulation, and 9 TFs were identified under wounding stress. In conclusion, several novel putative genes were found in Mongolian pine by PacBio ISO seq. Meanwhile, we also identified various genes that were resistant to S. noctilio venom, such as GAPDH, GPX, CAT, FL2, CERK1, and HSP83A, etc.

Pest categorisation of Sirex nitobei

The EFSA Panel on Plant Health performed a pest categorisation of Sirex nitobei (Hymenoptera: Siricidae), the nitobe horntail, for the territory of the EU. S. nitobei is not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072 but was identified as a potential regulated pest in a commodity risk assessment of Pinus thunbergii artificially dwarfed plants from Japan. This species is present in Japan (except Hokkaidō), the Republic of Korea and 13 Chinese provinces. S. nitobei attacks several Pinus species and has been reported less frequently on Abies firma and Larix spp., including L. leptolepis. The females oviposit into the sapwood. Eggs are deposited together with a phytotoxic mucus and a symbiotic fungus, Amylostereum areolatum or A. chailletii. The combined action of the venom and the fungus results in the death of the host trees. The fungus degrades the lignocellulosic components of the wood, and the larvae feed on the liquid fraction of the digested residues left by the fungus. All immature stages live in the hosts sapwood. The lifecycle of the pest lasts 1 year. S. nitobei can travel with conifer wood, wood packaging material or plants for planting, but these pathways from third countries are closed by prohibition. However, a derogation exists for artificially dwarfed Japanese black pine (Pinus thunbergii) from Japan, which therefore provides a potential pathway. Climatic conditions in several EU member states and host plant availability in those areas are conducive for establishment. The introduction of S. nitobei is potentially damaging for pines. Phytosanitary measures are available to reduce the likelihood of entry and further spread, and there is a potential for biological control. S. nitobei satisfies all the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.