Transcriptomic and Metabolomic Data Reveal the Key Metabolic Pathways Affecting Streltzoviella insularis (Staudinger) (Lepidoptera: Cossidae) Larvae During Overwintering

Streltzoviella insularis (Staudinger) (Lepidoptera: Cossidae) is a woodboring insect feeding on Fraxinus pennsylvanica, Sophora japonica, and Ginkgo biloba, as well as many other species used for urban greening and plain afforestation in northern China, including the temperate north. There is also a risk that S. insularis could spread through the transportation of seedlings, thereby increasing urban greening costs. However, how S. insularis increases the cold tolerance then reduces it to survive winter temperature below 0°C remains unclear. In the transcriptomic of S. insularis, we identified three profiles (profile 25, 27, and 13) whose trends related to the cold tolerance. We detected 1,783 differentially expressed genes (in profile 25) and identified 522 genes enriched in the AMPK signaling pathway. The metabolome analysis identified 122 differential metabolites. We identified four co-pathways, among which “Glycerophospholipid metabolism” was the pathway most enriched in differentially expressed genes and differential metabolites. The AMPK signaling and glycerophospholipid metabolism pathways play key roles in the natural overwintering physiological process of S. insularis larvae

Identification of putative Type-I sex pheromone biosynthesis-related genes expressed in the female pheromone gland of Streltzoviella insularis.

Species-specific sex pheromones play key roles in moth sexual communication. Although the general pathway of Type-I sex pheromone biosynthesis is well established, only a handful of genes encoding enzymes involved in this pathway have been characterized. Streltzoviella insularis is a destructive wood-boring pest of many street trees in China, and the female sex pheromone of this species comprises a blend of (Z)-3-tetradecenyl acetate, (E)-3-tetradecenyl acetate, and (Z)-5-dodecenyl acetate. This organism therefore provides an excellent model for research on the diversity of genes and molecular mechanisms involved in pheromone production. Herein, we assembled the pheromone gland transcriptome of S. insularis by next-generation sequencing and identified 74 genes encoding candidate key enzymes involved in the fatty acid biosynthesis, β-oxidation, and functional group modification. In addition, tissue expression patterns further showed that an acetyl-CoA carboxylase and two desaturases were highly expressed in the pheromone glands compared with the other tissues, indicating possible roles in S. insularis sex pheromone biosynthesis. Finally, we proposed putative S. insularis biosynthetic pathways for sex pheromone components and highlighted candidate genes. Our findings lay a solid foundation for understanding the molecular mechanisms underpinning S. insularis sex pheromone biosynthesis, and provide potential targets for disrupting chemical communication that could assist the development of novel pest control methods

Cold Tolerance in Pinewood Nematode Bursaphelenchus xylophilus Promoted Multiple Invasion Events in Mid-Temperate Zone of China

Pinewood nematode (Bursaphelenchus xylophilus) is a highly destructive invasive species, causing extensive economic and ecological losses across Eurasia. It has recently invaded mid-temperate zone of northern China, threating large areas of coniferous forests. Herein, we evaluated the physiological and molecular basis of cold tolerance in pinewood nematode isolates from different temperature zones of China. After exposure to −5 °C and −10 °C, the survival rates of five pinewood nematode isolates from different temperature zones were 93.94%–94.77% and 43.26%–45.58% after 8 h, and 93.04%–94.85% and 9.93%–10.56% after 24 h, without significant differences among isolates. In a comparison of an isolate from a mid-temperate zone and an isolate from a subtropical zone under gradient cooling, the survival rates remained steady at nearly 95% when minimum temperature ranged from −5 °C to −15 °C, with no significant difference between isolates. In addition, phylogenetic and population structure analyses based on whole genome resequencing data suggested that isolates from mid-temperate and warm temperate zones are clustered with different isolates from subtropical zone, with no obvious geographic pattern. We did not detect significant variation in cold tolerance ability and selected gene among pinewood nematode isolates from different temperature zones. The recently invaded pinewood nematodes in the mid-temperate zone of northern China may spread by multiple invasion events from southern China, without adaptive revolution. Our research implies that it is important to reinforce quarantine inspection to control the rapid spread of pinewood nematode

Cold Tolerance in Pinewood Nematode <i>Bursaphelenchus xylophilus</i> Promoted Multiple Invasion Events in Mid-Temperate Zone of China

Pinewood nematode (Bursaphelenchus xylophilus) is a highly destructive invasive species, causing extensive economic and ecological losses across Eurasia. It has recently invaded mid-temperate zone of northern China, threating large areas of coniferous forests. Herein, we evaluated the physiological and molecular basis of cold tolerance in pinewood nematode isolates from different temperature zones of China. After exposure to −5 °C and −10 °C, the survival rates of five pinewood nematode isolates from different temperature zones were 93.94%–94.77% and 43.26%–45.58% after 8 h, and 93.04%–94.85% and 9.93%–10.56% after 24 h, without significant differences among isolates. In a comparison of an isolate from a mid-temperate zone and an isolate from a subtropical zone under gradient cooling, the survival rates remained steady at nearly 95% when minimum temperature ranged from −5 °C to −15 °C, with no significant difference between isolates. In addition, phylogenetic and population structure analyses based on whole genome resequencing data suggested that isolates from mid-temperate and warm temperate zones are clustered with different isolates from subtropical zone, with no obvious geographic pattern. We did not detect significant variation in cold tolerance ability and selected gene among pinewood nematode isolates from different temperature zones. The recently invaded pinewood nematodes in the mid-temperate zone of northern China may spread by multiple invasion events from southern China, without adaptive revolution. Our research implies that it is important to reinforce quarantine inspection to control the rapid spread of pinewood nematode

The Relationship between Landscape Patterns and Populations of Asian Longhorned Beetles

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), is one of the most harmful invasive alien species attacking hardwood trees. Increasing human activities have caused changes in the landscape patterns of ALB habitats, disrupting the habitat balance and weakening landscape-driven pest suppression. However, the relationship between landscape patterns (compositional and structural heterogeneity) and ALB populations has not been defined. In this study, we used remote sensing data to calculate landscape metrics and combined them with ground survey data. Using a multivariable linear regression model and a linear mixed model, we analyzed the relationship between landscape metrics and ALB populations and between forest stands attributes and ALB populations. The study results indicated that largest patch index (LPI), mean radius of gyration (GYRATE_MN), mean shape index (SHAPE_MN), and Shannon&rsquo;s diversity index (SHDI) strongly influenced ALB populations at the landscape level. In addition, at the class level, only the forest class metrics LPI and aggregation index (AI) significantly impacted ALBs. The study also indicated that tree height (TH) and tree abundance (TREEAB) were good predictors of ALB populations

The Driving Forces of <i>Anoplophora glabripennis</i> Have Spatial Spillover Effects

Anoplophora glabripennis Motschulsky, 1854 (Asian longhorned beetle) does serious damage to forests. It has a long history and wide distribution area in China and is spreading there and elsewhere. Extreme climate events, such as cold surges and droughts, have had a promotive impact on Anoplophora glabripennis occurrence, but the spatial spillover effect of extreme climate events and other environmental factors on the occurrence of this pest has not yet been clarified. Two indices, namely, Standardized Precipitation Evapotranspiration Index (SPEI) and Low Temperature Index (LTI), were used to quantify the effects of drought and low-temperature freezing damage. Based on spatial panel data modeling, this study calculated the spatial spillover effect of environmental factors on the incidence of Anoplophora glabripennis in 666 counties in China’s central plains from 2002 to 2009. The factors examined included LTI, SPEI, average wind speed, hours of sunlight, Gross Domestic Product (GDP) of regional primary industry, population density, Normalized Difference Vegetation Index (NDVI), and pest control rate. Study results indicated that the impacts of environmental factors on the incidence rate of Anoplophora glabripennis are different. Low-temperature freezing damage, drought, wind speed, and pest control rate had a driving impact on pest incidence rates. Overall, the direct effect accounts for about 85% of the total effect, while the indirect effect accounts for about 15% of the total effect

The Driving Forces of Anoplophora glabripennis Have Spatial Spillover Effects

Anoplophora glabripennis Motschulsky, 1854 (Asian longhorned beetle) does serious damage to forests. It has a long history and wide distribution area in China and is spreading there and elsewhere. Extreme climate events, such as cold surges and droughts, have had a promotive impact on Anoplophora glabripennis occurrence, but the spatial spillover effect of extreme climate events and other environmental factors on the occurrence of this pest has not yet been clarified. Two indices, namely, Standardized Precipitation Evapotranspiration Index (SPEI) and Low Temperature Index (LTI), were used to quantify the effects of drought and low-temperature freezing damage. Based on spatial panel data modeling, this study calculated the spatial spillover effect of environmental factors on the incidence of Anoplophora glabripennis in 666 counties in China&rsquo;s central plains from 2002 to 2009. The factors examined included LTI, SPEI, average wind speed, hours of sunlight, Gross Domestic Product (GDP) of regional primary industry, population density, Normalized Difference Vegetation Index (NDVI), and pest control rate. Study results indicated that the impacts of environmental factors on the incidence rate of Anoplophora glabripennis are different. Low-temperature freezing damage, drought, wind speed, and pest control rate had a driving impact on pest incidence rates. Overall, the direct effect accounts for about 85% of the total effect, while the indirect effect accounts for about 15% of the total effect

The Relationship between Landscape Patterns and Populations of Asian Longhorned Beetles

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), is one of the most harmful invasive alien species attacking hardwood trees. Increasing human activities have caused changes in the landscape patterns of ALB habitats, disrupting the habitat balance and weakening landscape-driven pest suppression. However, the relationship between landscape patterns (compositional and structural heterogeneity) and ALB populations has not been defined. In this study, we used remote sensing data to calculate landscape metrics and combined them with ground survey data. Using a multivariable linear regression model and a linear mixed model, we analyzed the relationship between landscape metrics and ALB populations and between forest stands attributes and ALB populations. The study results indicated that largest patch index (LPI), mean radius of gyration (GYRATE_MN), mean shape index (SHAPE_MN), and Shannon’s diversity index (SHDI) strongly influenced ALB populations at the landscape level. In addition, at the class level, only the forest class metrics LPI and aggregation index (AI) significantly impacted ALBs. The study also indicated that tree height (TH) and tree abundance (TREEAB) were good predictors of ALB populations

Detecting Shoot Beetle Damage on Yunnan Pine Using Landsat Time-Series Data

Tomicus yunnanensis and Tomicus minor have caused serious shoot damage in Yunnan pine forests in the Yunnan Province of China. However, very few remote sensing studies have estimated the shoot damage ratio (SDR). Thus, we used multi-date Landsat satellite imagery to quantify SDRs and assess the possibility of using spectral indices to determine the beetle outbreak time and spread direction. A new threshold-based classification method was proposed to identify damage levels (i.e., healthy, slightly to moderately infested, and severely infested forests) using time series of moisture stress index (MSI). Permanent plots and temporal field inspection data were both used as references for training and evaluation. Results show that a single threshold value can produce a total classification accuracy of 86.38% (Kappa = 0.80). Furthermore, time series maps detailing damage level were reconstructed from 2004 to 2016. The shoot beetle outbreak year was estimated to be 2013. Another interesting finding is the movement path of the geometric center of severe damage, which is highly consistent with the wind direction. We conclude that the time series of shoot damage level maps can be produced by using continuous MSI images. This method is very useful to foresters for determining the outbreak time and spread direction

The larval sensilla on the antennae and mouthparts of five species of Cossidae (Lepidoptera)

Most species in Cossidae family can migrate from one host to a new one in later larval instars, which is different from other bark and wood boring insects. In this study, we selected Eogystia hippophaecolus (Hua, Chou, Fang and Chen, 1990), Deserticossus artemisiae (Chou et Hua, 1986), Deserticossus arenicola (Staudinger, 1879), Yakudza vicarious (Walker, 1865), and Streltzoviella insularis (Staudinger, 1892) to understand how these species locate new hosts in their larval stages. Scanning electron microscopy was used to determine the typology, morphology, number and distribution of sensilla on the antennae, maxillary palps, galeas, and labial palps of these five species. There were no differences in typology, morphology and number of sensilla between the five species. We observed antenna with three to four short sensilla basiconica, two sensilla chaetica, four sensilla basiconica, and one sensillum styloconicum. The maxillary palp had seven short sensilla basiconica, one sensillum digitiformium, and two sensilla placodea. The maxillary galea had three short sensilla basiconica, two sensilla styloconica, and one sensillum chaeticum. The labial palp had one short sensillum basiconicum and one sensillum styloconicum. Our results will provide a basis for further studies on the feeding, host-transfer behaviors, and electrophysiology of this group of forest pests.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author