Search Results (44)

Background: Pinus massoniana is a significant lipid-producing tree species in China and a susceptible host for both the pine wood nematode and its insect vector, Monochamus alternatus. The basic helix–loop–helix (bHLH) family of transcription factors play a crucial role in responding to both biotic and abiotic stresses. However, the role of bHLH in terpene-induced defense in P. massoniana remains poorly studied. Results: Transcriptome sequencing using DNA Nanoball Sequencing (DNBSEQ) and PacBio Sequel platforms was performed, revealing differences in gene expression in P. massoniana branch under the simulated feeding treatment of methyl jasmonate (MeJA) spraying. Fifteen bHLH genes were cloned and analyzed, among which eight highly upregulated PmbHLH genes showed similar temporal expression after MeJA treatment and M. alternatus adult feeding. Five highly upregulated bHLH genes with nuclear localization were highly expressed in P. massoniana after M. alternatus feeding and interacted with the promoter of the terpene synthase gene Pm TPS (−)-α-pinene, confirming their involvement in the defense response of P. massoniana against the M. alternatus adult feeding. Conclusions: Our results unveil the temporal changes and the regulation of the induced defense system in P. massoniana mediated by both MeJA signaling and M. alternatus feeding treatment. The potential application for transgenic experiments and the breeding of resistant species in the future were discussed. Full article

Herbivore-induced plant volatiles (HIPVs) play a pivotal role in mediating tritrophic interactions between plants, herbivores, and their natural enemies. Paracarophenax alternatus, a parasitic mite targeting the egg stage of Monochamus alternatus, has emerged as a promising biocontrol agent. However, its ability to detect Pinus massoniana-derived HIPVs for host insect localization remains unclear. G-protein-coupled receptors (GPCRs) may play a role in mediating the perception of HIPVs and associated chemosensory signaling pathways in mites. In this study, a total of 85 GPCRs were identified from P. alternatus. All GPCRs exhibited conserved transmembrane domains and stage-specific expression patterns, with 21 receptors significantly upregulated in viviparous mites. Combined with two previously identified odorant receptors (ORs), six candidate chemosensory receptors were selected for molecular dynamics simulations to validate their binding stability with key volatile compounds. The results demonstrate that specific GPCRs likely facilitate HIPV detection in mites, enabling precise host localization within dynamic ecological niches. Our findings provide critical insights into the molecular basis of mite–host interactions and establish a framework for optimizing P. alternatus-based biocontrol strategies against pine wilt disease vectors. Full article

Chitin synthase (CHS) plays a key role in chitin synthesis. CHS1 is ubiquitous in insects, and some studies have found that the RNA interference with CHS1 can hinder three types of molting processes (larva–larva, larva–pupa and pupa–adult). In the present study, the CHS1 of Monochamus alternatus was identified and characterized by a bioinformatics analysis. The developmental stage-specific expression of the MalCHS1 (Monochamus alternatus CHS1) gene was obtained by a RT-qPCR, and the corresponding dsRNA was designed for functional verification. The RNA interference experiment was conducted using the microinjection method, and the injection site was selected from the abdominal segments of fifth-instar larvae. The results showed that after silencing the CHS1 gene, the larvae of M. alternatus showed morphological abnormalities, such as the softening of the body wall, a transparent abdomen and the swelling of somites, indicating that MalCHS1 mediates the molting, growth and development of M. alternatus. RNAi-mediated MalCHS1 gene silencing may become a promising new biological pesticide that can provide a new target gene for pest control. Full article

Pine wilt disease, caused by the nematode Bursaphelenchus xylophilus, poses a significant threat to pine forests worldwide. Understanding the dynamics of its spread is crucial for effective disease management. In this study, we investigated the involvement of asymptomatic carrier trees in the expansion of pine wilt disease through a series of experiments. Cage-releasing experiments revealed that sexually immature Japanese pine sawyer beetles, Monochamus alternatus, feeding on healthy pine branches drops only a minimal number of nematodes (primary infection). However, sexually mature beetles, still harboring numerous nematodes, fly to weakened trees for breeding and extend their feeding activities to healthy pines around weakened trees, infecting them with nematodes and thus spreading the disease further. Inoculation experiments on field-planted black pine seedlings demonstrated that even a small number of nematodes can lead to a high occurrence of asymptomatic carrier trees. Our findings suggest that nematode infections transmitted by sexually mature Monochamus beetles significantly contribute to the expansion of pine wilt damage and play a crucial role in the persistence of asymptomatic carrier trees. This conclusion is based on cage-release experiments demonstrating nematode transmission by mature beetles and inoculation experiments highlighting the conditions leading to asymptomatic carrier trees. Full article

To understand the spread of the pine wood nematode Bursaphelenchus xylophilus (Steiner and Buhrer, 1934; Nickle, 1970) and identify infected trees, the dispersal ability of insects was examined. In this study, the effects of sex, adult age, and morphological traits on the flight performance (such as flight distance, time, and speed) of Monochamus alternatus (Hope, 1843) were investigated using flight mills. Over a period of 8 weeks, a total of 42 newly emerged adult beetles were tethered to flight mills once a week. Flight distance and time were recorded for 2 h during each session. The total flight distance of individuals that flew more than 100 m during each session was calculated. The results showed that females flew an average of 6.65 km, for 59.6 min, while males flew an average of 9.89 km, for 85.8 min. In a single flight experimental session, both sexes could fly up to approximately 2 km and were found to fly at an average speed of 1.9 m s⁻¹. In our principal component analysis (PCA), the first and second principal components were found to be highly correlated with the sex, morphological traits, and flight performances of M. alternatus. This study demonstrates that the flight ability of M. alternatus varies significantly according to body size and sex, which is fundamental and crucial for understanding the dispersal patterns of pine wilt disease. Full article

To examine the role of asymptomatic infected trees in the spread of pine wilt disease (PWD), we established two study sites in a coastal black pine forest in 2020: one in a heavily damaged site and the other in a slightly damaged site. Half of the trees in each site were treated with a nematicide injection to suppress nematode activity. Tree health, assessed by resin exudation and external symptoms, was monitored for four years. In the slightly damaged site, asymptomatic infected trees emerged within 20 m of infected trees, and even with nematicide treatment, trees within 2 m of infected trees became asymptomatic infected. However, nematicide treatment allowed temporarily asymptomatic infected trees to survive or recover. These findings suggest that combining nematicide injection with the felling of neighboring infected trees can effectively suppress PWD. Full article

Pine wilt disease, caused by the pinewood nematode, affects Pinus densiflora, P. koraiensis Siebold and Zucc., and P. thunbergii Parl. in South Korea. It is primarily spread by vectors such as Monochamus alternatus Hope and M. saltuarius (Gebler). However, biological control research in this context remains limited in South Korea. We identified 15 parasitoids of these vectors, namely, two ectoparasitic larval parasitoids, Cyanopterus flavator (Fabricius) and Spathius verustus Chao, both in Braconidae, Hymenoptera. A field survey was conducted in Pohang from 2018 to 2020 to elucidate the ecological and biological characteristics of these parasitoids. The average parasitism rates of C. flavator were 6.3% and 1.0%, whereas those of S. verustus were 0.7% and 0.5% on M. alternatus and M. saltuarius, respectively. Both C. flavator and S. verustus appeared to prefer M. alternatus to M. saltuarius, but a statistically significant difference was observed only for C. flavator (p < 0.001). The peak season and tree height with the highest parasitism rate of C. flavator coincided with the period when M. alternatus larvae lived beneath the bark and the highest larval density of M. alternatus and M. saltuarius occurred in pine trees. These findings provide valuable information for determining the optimal release time and height for C. flavator to achieve effective biological control. Full article

Monochamus alternatus Hope and Arhopalus rusticus (L.) are important stem-boring pests that co-occur on weakened Pinus spp. Their larvae damage the xylem and phloem of the trunks and branches. At present, the consequences of the interspecific relationship between two longicorn beetles on the same host of Pinus trees are unclear. The population dynamics and spatial distribution of these two species on Pinus thunbergii trees were investigated to clarify the ecological niches and interspecific relationship of two longicorn beetles on the different degrees of decline in P. thunbergii trees. The results showed temporal niche overlap values from 0.02 ± 0.01 to 0.05 ± 0.02, suggesting a very high degree of temporal ecological niche segregation and no competition in temporal niche resources. There is significant interspecific competition between the two longicorn beetles in spatial distribution, and the spatial niche overlap values are 0.67 ± 0.11 and 0.61 ± 0.09 in the middle and late stages of the decline in P. thunbergii trees, respectively. Full article

Monochamus alternatus, a pest posing a serious threat to coniferous species, such as Pinus massoniana, has had devastating effects on pine forests due to its association with Bursaphelenchus xylophilus. The creation of unique simple sequence repeat (SSR) primers for M. alternatus is crucial, as there has been little study of the species’ phylogeography. The aim of this study was to identify and create polymorphic SSR primers by sequencing samples of M. alternatus obtained from three different sampling points using the restriction site-associated DNA sequencing (Red-seq) approach. Subsequently, supplementary samples were integrated, and genetic typing was performed utilizing the identified polymorphic primers. Through comprehensive analysis, a total of 95,612 SSR loci were identified. Among these, mononucleotide repeats (51.43%), dinucleotide repeats (28.79%), and trinucleotide repeats (16.74%) predominated among the SSR motif types. Ultimately, 18 pairs of SSR primers were screened out, demonstrating stable amplification and high polymorphism. Genetic typing revealed that the mean number of alleles (Na) for these primer pairs ranged from 3 to 8, observed heterozygosity (Ho) ranged from 0.133 to 0.733, polymorphic information content (PIC) ranged from 0.294 and 0.783, and Shannon’s index (I) ranged from 0.590 to 1.802. This study effectively produced 16 pairs of SSR primers that can be applied to different populations of M. alternatus. As a result, important tools for furthering studies on the phylogeography of pine wood nematodes, creating genetic maps, gene mapping, and carrying out in-depth investigations into gene function have been made available. Full article

This study predicted the potential habitats of Monochamus alternatus, a known vector of Bursaphelenchus xylophilus, utilizing its occurrence points and environmental variables—ecoclimatic indices and terrain variables. SSP2-4.5 and SSP5-8.5 scenarios were applied to predict the potential habitat under climate change. We secured the 20,514 occurrence points of Monochamus alternatus among the points with geographic coordinates of PWD-affected trees (2017–2022). The maximum entropy model (MaxEnt) and ensemble model (ensemble) were used to identify and compare the variability of potential habitats in the baseline period, near future, intermediate future, and distant future. At the outset, both the MaxEnt and the ensemble models showed a high model fit, and the ensemble was judged to be relatively superior. Next, both models showed that the habitat will expand northward according to climate change scenarios. Finally, the binary maps were superimposed to examine the differences between individual and multiple models; both models showed similar distributions in the baseline period and near future. Nonetheless, MaxEnt tended to overestimate expansion in the intermediate and far future. In the future, it is expected that the accuracy and reliability of forecasts can be improved by building optimized models to reduce uncertainty by supplementing field data and collaborating with model experts. Full article

MaltAtt-1 is an antimicrobial peptide isolated from Monochamus alternatus with nematocidal activity against pine wood nematode. In this study, a eukaryotic expression system based on Komagataella phaffii GS115 was established, and its secretory expression of MaltAtt-1 was realized. The basic properties and secondary and tertiary structures of the antimicrobial peptide MaltAtt-1 were identified by bioinformatics analysis. MaltAtt-1 is a hydrophilic stable protein, mainly composed of an α-helix (Hh), β-folds (Ee), and irregular curls (Cc). The optimal fermentation conditions for MaltAtt-1 were determined by a single-factor test and the Box–Behnken response surface method, including an induction time of 72 h, induction temperature of 30 °C, culture medium of pH 7.6, methanol volume fraction of 2.0%, and an initial glycerol concentration of 1%. The stability of MaltAtt-1 indicated its resistant to UV irradiation and repeated freezing and thawing, but the antibacterial activity decreased significantly under the influence of high temperature and a strong acid and base, and it decreased significantly to 1.1 cm and 0.83 cm at pH 2.0 and pH 10.0, respectively. The corrected mortality of B. xylophilus achieved 71.94% in 3 h at a concentration of 300 mg·L⁻¹ MaltAtt-1 exposure. The results provide a theoretical basis for the antimicrobial peptide MaltAtt-1 to become a new green and efficient nematicide. Full article

N⁶-methyladenosine (m⁶A) RNA modification is the most prevalent form of RNA methylation and plays a crucial role in plant development. However, our understanding of m⁶A modification in Masson pine (Pinus massoniana Lamb.) remains limited. In this study, a complete analysis of m⁶A writers, erasers, and readers in Masson pine was performed, and 22 m⁶A regulatory genes were identified in total, including 7 m⁶A writers, 7 m⁶A erases, and 8 readers. Phylogenetic analysis revealed that all m⁶A regulators involved in Masson pine could be classified into three distinct groups based on their domains and motifs. The tissue expression analysis revealed that the m⁶A regulatory gene may exert a significant influence on the development of reproductive organs and leaves in Masson pine. Moreover, the results from stress and hormone expression analysis indicated that the m⁶A regulatory gene in Masson pine might be involved in drought stress response, ABA-signaling-pathway activation, as well as resistance to Monochamus alternatus. This study provided valuable and anticipated insights into the regulatory genes of m⁶A modification and their potential epigenetic regulatory mechanisms in Masson pine. Full article

The Japanese pine sawyer Monochamus alternatus serves as the primary vector for pine wilt disease, a devastating pine disease that poses a significant threat to the sustainable development of forestry in the Eurasian region. Currently, trap devices based on informational compounds have played a crucial role in monitoring and controlling the M. alternatus population. However, the specific proteins within M. alternatus involved in recognizing the aforementioned informational compounds remain largely unclear. To elucidate the spatiotemporal distribution of M. alternatus chemosensory-related genes, this study conducted neural transcriptome analyses to investigate gene expression patterns in different body parts during the feeding and mating stages of both male and female beetles. The results revealed that 15 genes in the gustatory receptor (GR) gene family exhibited high expression in the mouthparts, most genes in the odorant binding protein (OBP) gene family exhibited high expression across all body parts, 22 genes in the odorant receptor (OR) gene family exhibited high expression in the antennae, a significant number of genes in the chemosensory protein (CSP) and sensory neuron membrane protein (SNMP) gene families exhibited high expression in both the mouthparts and antennae, and 30 genes in the ionotropic receptors (IR) gene family were expressed in the antennae. Through co-expression analyses, it was observed that 34 genes in the IR gene family were co-expressed across the four developmental stages. The Antenna IR subfamily and IR8a/Ir25a subfamily exhibited relatively high expression levels in the antennae, while the Kainate subfamily, NMDA subfamily, and Divergent subfamily exhibited predominantly high expression in the facial region. MalIR33 is expressed only during the feeding stage of M. alternatus, the MalIR37 gene exhibits specific expression in male beetles, the MalIR34 gene exhibits specific expression during the feeding stage in male beetles, the MalIR8 and MalIR39 genes exhibit specific expression during the feeding stage in female beetles, and MalIR8 is expressed only during two developmental stages in male beetles and during the mating stage in female beetles. The IR gene family exhibits gene-specific expression in different spatiotemporal contexts, laying the foundation for the subsequent selection of functional genes and facilitating the full utilization of host plant volatiles and insect sex pheromones, thereby enabling the development of more efficient attractants. Full article

Adults of the pine sawyer Monochamus alternatus are the primary vector of Bursaphelenchus xylophilus, the causative agent of pine wilt disease. A sawyer subspecies in Taiwan (abbreviated ‘T’) has two generations a year (bivoltinism) due to facultative diapause, whereas another subspecies in Japan (abbreviated ‘J’) has a one- or two-year life cycle due to obligate diapause. T, with two infection periods a year, will cause more severe disease epidemics than J if it is introduced into Japan. Inter-subspecies hybridization may inhibit the expression of bivoltinism because many F1 hybrids induce diapause. To predict the effects of introducing T into Japan, the present study investigated copulation duration and late-male sperm precedence to fertilize eggs. The results indicated that a single copulation for more than 65 s supplied sufficient sperm to fertilize a lifetime production of eggs. The incidence of larval diapause was 0.15 for the offspring of T females that mated with a T male and increased to 0.292–0.333 after remating with a J male, while the incidence of larval diapause was 0.900–1.000 for hybrids from T females mated with a J male. Consequently, the estimated proportion of second-male sperm used by T females was 0.185–0.217. The effects of introducing T populations into Japan on the severity of disease epidemics were also discussed. Full article

Monochamus alternatus is a serious trunk-boring pest. The isolation and utilization of entomopathogenic fungi to manage M. alternatus is important. Here, a new strain GQH6 of Metarhizium robertsii, isolated from the Loess Plateau, was identified morphologically and molecularly. The virulence of the strain GQH6 against the third-instar larvae of M. alternatus was studied. Then, the pathological process, including symptom observation and histopathological observation, was also researched. The corrected mortality was 100% at 10⁹ and 10⁸ conidia/mL, and 88.89 ± 5.88% at 10⁷ conidia/mL. The LC50 was 1.93 × 10⁶ conidia/mL and the LC90 was 1.35 × 10⁷ conidia/mL. And the LT50 of the strain GQH6 was 3.96 days at 10⁹ conidia/mL, and 4.99 days at 10⁸ conidia/mL. These virulence indices showed high virulence against M. alternatus larvae. In addition, the symptoms of the infected M. alternatus larvae were obvious. After one day, dark spots appeared and increased in number. By four days, white mycelia appeared. Finally, the larvae body became green. Similarly, the histopathological changes after infection were obvious, mainly manifested in muscle tissue rupture, adipose tissue fracture and midgut disintegration. These results demonstrated that the M. robertsii strain GQH6 isolated from the Loess Plateau was highly virulent against M. alternatus larvae of the third instar. Full article