Spodoptera frugiperda is a major agricultural pest, and the 1st -3rd instar S. frugiperda have spinning behaviour and can drift to adjacent plants with the help of the wind. The present study found that azadirachtin can affect this behaviour, and the mechanism by which azadirachtin affects the spinning behaviour of S. frugiperda has been studied. In this study, the 3rd instar larvae were exposed to azadirachtin, and the pathological changes in the silk glands of S. frugiperda and the differences in their metabolites were analysed by pathological sectioning, transmission electron microscopy, metabolomics and other experimental methods. The results showed that azadirachtin can affect the silk gland of S. frugiperda. After 48 h of treatment with azadirachtin, the silk gland lumen of S. frugiperda appeared vacuolated, and KEGG showed that 31 different metabolites were identified, of which 12 were upregulated and 19 were downregulated. These metabolites were enriched in 15 different metabolic pathways, which pathways indicated that the silk gland of S. frugiperda was closely related to the formation of fatty acids and to energy metabolism in the process of silk formation. This research can further explain the spinning mechanism of insects and provide a research basis for determining the spinning, cocooning, and transfer damage mechanisms of many agricultural and forestry pests.
Research Article
Azadirachtin inhibits the development and metabolism of the silk glands of Spodoptera frugiperda and affects spinning behaviour
https://doi.org/10.21203/rs.3.rs-1410950/v1
This work is licensed under a CC BY 4.0 License
Version 1
posted 21 Mar, 2022
You are reading this latest preprint version
Azadirachtin
Spodoptera frugiperda
metabolomics
silk gland
spinning behaviour
The 1st -3rd instar Spodoptera frugiperda can spit and drift to neighbouring plants.
Azadirachtin causes a decrease in the amino acids histidine, glycine, and leucine in the silk glands of Spodoptera frugiperda.
Azadirachtin causes insect silk to break more easily.
Feeding with azadirachtin for 72 h reduces Spodoptera frugiperda spinning.
Azadirachtin can affect the development of the silk glands of Spodoptera frugiperda and thus affect silking behaviour.
Spinning behaviour plays an important role in the life history of many species of insects. Some insects use silk to form cocoons to resist potential natural enemies and prevent the microbial invasion and infection of pupae. The typical example is Bombyx mori (Fedi et al. 2003). Some insects use silk to roll leaves to complete feeding, pupation and other behaviours; for example, the larvae of the Pyralidae, such as Cnaphalocrocis medinalis and Sylepta derogata, use leaf rolls to hide themselves for feeding, pupation and other behaviours to avoid natural enemies or reduce the impact of bad weather (Su et al. 2015). Some insects use silk to suspend themselves to avoid danger. In addition, some insect larvae spin silk for the purpose of transfer. Many Lepidoptera use silk spinning in the larval stage to achieve larval dispersal. For example, a newly hatched larva of Chilo partellus can float in the air by relying on a silk thread that it spins and use the wind to “float” to another plant for transfer (Berger 1989). The larvae of Lymantria dispar can use strands of silk from their heads to form a “silk ladder” to assist in climbing (Roden 1993). The role of insect spinning involves many aspects, including growth, development and feeding.
Insect silk is composed of silk fibroin, sericin, external wax and pigments and other impurities. It exists in the form of liquid in the insect body. When it is secreted from the body, it is rotated or sheared to form silk (Asakura et al. 2020). Silk fibroin is the main component of insect silk. It is a natural biomolecule with no physiological activity. Its amino acid structure is relatively simple, and the molecules assemble easily, so silk fibroin has a certain degree of crystallinity. Differences in the ratio of amino acids in insect silk will also cause differences in silk quality (Fedi et al. 2003). If the proportion of small side chain amino acids in silk is high, the peptide chains are arranged neatly. Conversely, large side chain amino acids in silk will reduce the tightness of the aggregated structure of the silk, reduce the crystallinity of the silk, and even make the silk less elastic and easy to break (Sen and Babu K 2004; Sutherland et al. 2010). It has been reported that mutations in both the Fib-H (fibroin chain high) gene and the Fib-L (fibroin chain light) gene can lead to a decrease in silk production, which shows that Fib-H and Fib-L are both key genes that control silk fibroin secretion (Takei et al. 1984). In addition, some metal ions may affect the quality of silk. Studies have found that cerium can reduce the damage caused to silk glands by phoxim, promote protein synthesis, improve the antioxidant capacity of silk glands, and promote Bombyx mori silking (Li et al. 2015). The addition of K+ or Cu2+ to the silk fibroin solutions can induce the conformational transitions of silk fibroin of the silkworm to β-sheet, thereby improving the mechanical performance of the silk fibre (Wang et al. 2017). Juvenile hormone and ecdysone can also affect silking behaviour through the modulation of Fib-L, Fib-H, P25 and other spinning-related genes at the mRNA level (Sehnal and Akai 1990; Shi et al. 2020).
Spodoptera frugiperda belongs to the family Lepidoptera Noctuidae, which originates in tropical America and has the ability to migrate to seek food (Paredes-Sánchez et al. 2021). S.frugiperda is a highly polyphagous pest that feeds on more than 80 plants including corn, sorghum, rice, sugar cane, and vegetables, and causes considerable economic loss (Miranda et al. 2022; Sisay et al. 2019). Despite different characteristics on different host plants, it usually consists of two morphologically identical strains, the corn strain (C strain) and the rice strain (R strain). At present, the main type of invasion in China is the C strain, which mainly feeds on corn, cotton, and sorghum (Liu et al. 2019; Pashley 1986). Most plant extracts are nontoxic and nonpathogenic to animals and humans but can be used as an alternative to synthetic insecticides for pest management (Sisay et al. 2019). Azadirachtin is a biopesticide extracted from the neem tree. It is a broad-spectrum, low-toxicity, and easily degradable insecticide recognised worldwide. It has repellent and anti-feeding effects on many insects (Lin et al. 2021; Qin et al. 2021). At present, the control of S.frugiperda is still mainly dependent on chemical control, and resistance has become a major problem. It has been reported that azadirachtin has antifeeding and growth and development inhibition effects on S. frugiperda. However, the mechanism by which azadirachtin affects the silk gland of S. frugiperda has not been studied and reported.
Treating S. frugiperda with a low concentration of azadirachtin will affect its silk gland and in turn its spinning behaviour. In this study, the quality of the silk and silk gland was studied by scanning electron microscopy, metabolomics and other research methods. The influence of azadirachtin on the development of the silk gland and spinning of S. frugiperda was explained from physiological and metabolomic perspectives.
2.1. Reagents and insects
Azadirachtin A (purity 95%) was purchased from Sigma (CAS: 11141-17-6), and stored at -20 °C. Azadirachtin powder was dissolved in 20% DMSO and added to the artificial diet, which was thoroughly mixed to evenly distribute the azadirachtin and stored in a 4 °C refrigerator. S.frugiperda grow in our laboratory were reared on artificial diets at 25 ± 1 °C and 65 ± 5% relative humidity (RH) under a 16:8 h light/dark photoperiod. The 3rd instar S.frugiperda at the same developmental level were selected for the experiment.
2.2. Morphology of silk and silk gland of Spodoptera frugiperda
The 3rd instar S. frugiperda were placed in 1×PBS and dissected under a light microscope. The surrounding excess tissue was removed to expose the intact silk gland, and the anterior, middle and posterior of the silk gland were observed. The silk of the 3rd instar S. frugiperda was collected with a capillary, and after gold plating, samples were viewed under an EVO MA 15 scanning electron microscope. Ten insects were used in each experiment for a total of three replicates.
2.3. Observation of spinning behaviour
To study the responses of spinning behaviour to the different treatments, the 3rd instar larvae of S. frugiperda were fed 0.3 mg/kg or 3 mg/kg azadirachtin for 24, 48, and 72 h, and another group fed the DMSO artificial diet was used as the control. Some of the larvae from the different treatments were collected. Each group of 30 larvae was replicated three times. The number of S. frugiperda larvae spinning after treatment for 24, 48, and 72 h and the spinning rate were calculated with the following formula:
S: spinning rate,
N: number of S.frugiperda spinning,
M: total number of living S.frugiperda.
2.3. Scanning electron microscopy
The 3rd instar S.frugiperda were selected and starved for 6 h and then fed 0.3 mg/kg azadirachtin artificial diet and azadirachtin-free artificial diet for 48 h. The treated insects were placed on the capillary and allowed to hang naturally, and the silk was collected with the capillary. The samples were immediately fixed to the substrate with copper conductive adhesive, plated with gold and observed under a Verios 460 field emission scanning electron microscope (10 insects in each experiment, three replicates).
2.4. Pathological section analysis and transmission electron microscopy
The larvae were treated as described in 2.3, and the samples after different treatment times were collected and dissected in 1×PBS. The dissected silk gland sample was fixed in 4% paraformaldehyde solution at room temperature for more than 24 h, dehydrated in a graded acetone series (75%, 85%, 90% and 95%) and embedded in paraffin. The trimmed wax block was cooled on a -20 °C freezing table, and the modified tissue chip wax block was sliced on a paraffin slicer at a thickness of 4 μm, and baked in the oven at 60 ℃. After the water-baked dried wax was melted, it was removed and stored at room temperature. Sections were stained with haematoxylin and eosin (HE), then observed and photographed with a Nikon DS-U3 photomicroscope.
A sharp blade was used to cut and harvest fresh silk glands quickly within 1-3 min, and 1 mm3 tissue blocks were transferred to an EP tube containing fresh TEM fixative and fixed at 4 °C for preservation. The tissues were then washed using 0.1 M PBS (pH 7.4) 3 times for 15 min each and subjected to postfixation with 1% osmium tetroxide in 0.1 M PBS (pH 7.4) for 2 h at room temperature in the dark, then rinsed again in 0.1 M PBS (pH 7.4) 3 times. The samples were dehydrated in a graded acetone series (30%, 50%, 70%, 80%, 95% and 100%) followed by two changes of 100% ethanol for 20 min and embedded in Araldite resin. Ultrathin sections were contrasted with 2% uranium acetate saturated alcohol solution and 2.6% lead citrate and finally observed and photographed with a Hitachi HT7800 transmission electron microscope.
2.5. Untargeted metabolomics analysis by LC/MS
The 3rd instar S. frugiperda in the treatment continuously ingested 0.3 mg/kg azadirachtin for 48 h, and the control was fed a 20% DMSO artificial diet. Under a light microscope, the silk glands of S. frugiperda were dissected on ice to remove the surrounding nerves, fat and other irrelevant tissues. Then, 1×PBS prepared with precooled enzyme-free water was quickly used to clean the stains on the surface of the tissue, the liquid on the surface was soaked up, and the sample was quickly placed into a precooled, enzyme-free -192 ℃ ultralow temperature-resistant freezing tube with a threaded mouth, quick-frozen in liquid nitrogen for 3-4 h, and then placed at -80 ℃ for long-term storage. Each sample contained 120 silk glands with 6 biological replicates.
Extraction of metabolites: A 100 mg tissue sample was weighed (adjusted according to the actual situation) and ground with liquid nitrogen. The collected samples were thawed on ice, and 20 μL of sample was extracted with 120 μL of precooled 50% methanol, vortexed for 1 min and incubated at room temperature for 10 min. The extraction mixture was then stored overnight at ‐20 °C. After centrifugation at 4,000 ×g for 20 min, the supernatants were transferred into new 96‐well plates. The samples were stored at ‐80 °C prior to LC‐MS analysis. In addition, pooled QC (quality control) samples were prepared by combining 10 μL of each extraction mixture.
2.6. Statistical analysis
GraphPad Prism 7(GraphPad Corporation, Northside Dr. Suite, USA) was used to draw graphs. All statistical analyses were implemented using SPSS 24.0.0 (IBM Corporation, Somers, NY, USA). The significance of differences was computed by one-way ANOVA, and the results with P <0.05 were regarded as statistically significant.
3.1. Silk and silk gland of Spodoptera frugiperda
The 1st-3rd instar larvae of S.frugiperda can spit silk and float in the air to move to plants on the wind. Third instar larvae were placed in a capillary tube and shaken gently, which caused the larvae to spit and droop (Fig. 1. a). Insect silk is a composite fibre with silk fibroin as the centre and several layers of sericin on the outside. Sericin is divided into inner-layer sericin, middle-layer sericin and outer-layer sericin (Fig. 1. c).The morphology of the silk gland can be divided into three regions: the posterior silk gland (PSG), middle silk gland (MSG) and anterior silk gland (ASG). In addition, there is a spigot at the front of the silk gland. Pairs of glands are located on the ventral side of the intestine on both sides, and the spinner is located in the insect’s mouth (Fig. 1. b). Silk fibroin is synthesized from the posterior silk gland, and sericin is synthesized from the middle silk gland, which is processed by the anterior silk gland and finally emerges from the mouth as solid silk through the spinner. The anterior silk gland of S.frugiperda consists of elongated ducts, and there is no obvious demarcation point between the middle and posterior silk gland, presenting a typical N-shaped structure. The posterior silk gland is short and slender, without folding or bending. By observing the morphology of the silk gland of S.frugiperda, we found that it does not have a developed posterior silk gland like Bombyx mori. The development of the posterior silk gland may have a close relationship with the number of insects spinning, and the underdeveloped posterior silk gland limits the ability to synthesize silk. Therefore, S.frugiperda cannot spin as large an amount of silk as Bombyx mori (Fig. 1. b).
3.2. Effects of trace azadirachtin on Spodoptera frugiperda spinning behaviour
Scanning electron microscopy observation of the 3rd instar S.frugiperda showed that the surface of the control S.frugiperda silk was smooth and free of cracks. After the insect silk is synthesized in the bilateral silk glands, it is processed and compressed by the silk press and spigot to a solid state. In this process, it is possible for the double-sided silk gathered in the spinner not to be well fused, resulting in depressions in the middle of the silk (Fig. 2. a, c). After exposure to traces of 0.3 mg/kg azadirachtin for 48 h, there was obvious unevenness on the surface of the silk. The sericin in the anterior silk gland did not perfectly encapsulate the silk fibroin. Compared with the control group, the sol phenomenon was more prone to occur, and swelling and rupture occurred more easily (Fig. 2. b, d). Analysis of the spinning of the 3rd instar S. frugiperda showed that there was no significant difference in spitting ability after 24 h of feeding on azadirachtin. The spinning rate of S. frugiperda fed 0.3 mg/kg azadirachtin increased at 48 h, while no difference was observed at 3 mg/kg, however, the spinning rate was significantly reduced after 72 h at both doses (Fig. 2. e).
3.3. Comparison of the silk gland in terms of morphology, pathology and ultrastructure
Under normal conditions, S.frugiperda grows gradually, but larval growth and development are inhibited by feeding on azadirachtin (Fig. a, d, g, S1). To further understand the effect of azadirachtin on the spinning behaviour of the S.frugiperda silk gland, pathological sections of the silk gland of S.frugiperda were obtained. The silk gland is the site of silk formation and storage, which is closely related to the secretion of silk. The pathological sections showed that the control had no abnormal pathological changes, the gland cavity was full, the entire silk gland was not damaged, and the silk glands gradually became larger as the larvae grew (Fig. 3. b, e, h). After 24 h of exposure to 0.3 mg/kg azadirachtin, the silk gland was still normal, and the protein still aggregated in large amount (Fig. 3. c). However, after 48 h, it could be clearly observed that the protein aggregation in the silk gland was significantly weakened, and obvious vacuolation (the gap between the membrane and the protein aggregation) was observed in the lumen of the silk gland (Fig. 3. f). After 72 h of exposure to azadirachtin, a significant reduction in protein was observed, and the glandular membrane ruptured (Fig. 3. i).
In addition, TEM of the silk gland ultrastructure showed that the cell structure of the control was normal, the cell membrane was intact, the endoplasmic reticulum was abundant and distributed, and a large amount of rough endoplasmic reticulum was present (Fig. 4. a), whereas in the group treated with azadirachtin, after 48 h, the silk gland epithelial cells were mildly to moderately oedematous, the chromatin was unevenly distributed, intracellular matrix electron density was reduced, vacuolization appeared (shown by the red arrow), and the silk gland cell membrane was locally damaged. The organelles in the cytoplasm were swollen, and the nucleus was irregularr (Fig. 4. b). These data indicate that azadirachtin caused damage to the silk gland, which may further affect spinning behaviour.
3.4. Metabolomics analysis
The metabolites in the silk glands of S.frugiperda after feeding on azadirachtin were analysed. XCMS software was used for peak extraction and quality control, and CAMERA was used for additive ion annotation of the extracted substances (Fig. S2). MetaX software was used for metabolite identification (database matching identification for primary mass spectrometry information and secondary mass spectrometry information for matching identification with an in-house standard product database). The annotated metabolites were mapped to the Kyoto Encyclopedia of Genes and Genomes (KEGG) ID and the Human Metabolome Database (HMDB) to examine the physicochemical properties and biological functions of the metabolites (Fig. S3). MetaX software was used to quantify metabolites and screen differential metabolites. Pathways with P <0.05 were considered to be significant.
After treatment of the 3rd instar S.frugiperda with 0.3 mg/kg azadirachtin for 48 h, the metabolome data of the silk glands revealed a total of 5038 differential metabolites, with 1687 metabolites upregulated and 3351 metabolites downregulated (Fig. 5. b, Table S1). Among them were 154 differential secondary metabolites (Fig. S4, Table S2), 87 of which were enriched in metabolic pathways, indicating that the metabolic rate in the silk gland was very high, 17 were enriched in the biosynthesis of amino acids, and 13 were involved in the ABC transport pathway, which indicates that transport processes in the silk gland were also very active (Fig. 5. a).
KEGG pathway enrichment analysis showed that 30 differential metabolites were identified, of which 12 were upregulated and 18 were downregulated, mainly in four categories: lipids and lipid-like molecules, organoheterocyclic compounds, phenylpropanoids and polyketide, and organic acids and derivatives. The metabolites enriched in the silk gland were L-citrulline, genistin, PC(20:4(8Z,11Z,14Z,17Z)/16:1(9Z)), urocanic acid, linoleic acid, ricinolic acid, alpha-dimorphecolic acid, 9,10-epoxyoctadecenoic acid, riboflavin, testosterone propionate, coumarin, and (9S,10S)-9,10-dihydroxyoctadecanoate(9S,10S)-9,10 (Fig. 6. a). The decreased metabolites were His-Leu, guanine, lysoPE 16:1, suberic acid, pergolide, Gly-Leu, dodecanedioic acid, jasmonic acid, aflatoxin M1, adipic acid, sporol, azelaic acid, quinidine, lysoPI 20:5, sebacic acid, trimethoprim, phlorizin, and strychnine (Fig. 6. b). The results showed enrichment in 15 different pathways, including choline metabolism in cancer, arginine biosynthesis, histidine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, biosynthesis of amino acids, and aminoacyl-tRNA biosynthesis (Fig. 5. c).
As a plant-derived insecticide, azadirachtin has the characteristics of high efficiency, low toxicity, no residue and no pesticide resistance (Kumar et al. 2010). Many studies have shown that azadirachtin has antifeeding, contact killing, and stomach poisoning effects, inhibits growth and development, and affects ovarian development in a variety of pests (Schmutterer 1990). In this study, we found that azadirachtin has an effect on the spinning of S. frugiperda. When S. frugiperda was exposed to 0.3 mg/kg azadirachtin, its silk gland was damaged. Pathological section analysis showed that there were no obvious pathological changes in the silk gland of 3rd instar S. frugiperda after continuous ingestion of azadirachtin for 24 h. Changes occurred after 48 h and 72 h, resulting in a decrease in protein in the glands and severely ruptured glandular membranes. We hypothesise that the raw materials for silk synthesis are also affected at this time. Protein synthesis is one of the most complex biochemical processes. It involves hundreds of different proteins and the participation of more than 30 RNA molecules. Amino acids must be activated before they can be incorporated into polypeptides. Aminoacyl-tRNA synthetase catalyses the reaction to form aminoacyl-tRNA, which is the first reaction in protein synthesis. This process needs to consume ATP for energy (Fang and Guo 2017). KEGG analysis showed that the aminoacyl-tRNA biosynthesis pathway had a significant impact on the S. frugiperda silk gland.
It has been reported in the literature that the silk gland of Bombyx mori is a specialised organ for the production of silk protein. The highly specific structure ensures that the silk gland can synthesize and secrete silk protein quickly and in large quantities (Qian et al. 2021). The spinneret does not participate in the secretion of silk protein, and its function is mainly to regulate the Bombyx mori spinning behaviour and control the diameter of silk fibre (Mortimer et al. 2013). Silk fibres are composed of two main types of silk proteins, silk fibroins and sericins. Silk fibroin is the core protein of the fibre and is hydrophobic; it is synthesized in the posterior silk gland, secreted into the lumen of the posterior silk gland, and then transported to the middle silk gland and stored in the lumen until spinning. Silk sericin, which is wrapped around silk fibroin and is hydrophilic, is synthesized in the middle silk gland. The anterior silk gland does not participate in the synthesis of silk protein; it processes silk fibroin and sericin and finally spits out silk from the mouth in a solid state through a spinner (Xia et al. 2014). Damage to the silk gland may affect the synthesis of silk fibroin, sericin and other substances in the silk gland. Transmission electron microscopy also showed that the damage affected silk gland cells. We found that when S. frugiperda were fed azadirachtin for 72 h, their spinning rate decreased, which suggests that azadirachtin is able to interfere with their spitting ability by damaging the silk glands. When insect silk glands are sufficiently damaged, their ability to synthesize silk protein to form silk threads will be weakened, and the output and quality of the silk produced will decrease (Santorum et al. 2020).
We also found that feeding on 0.3 mg/kg azadirachtin for 48 h, increased the spinning rate, and the metabolome showed changes in the metabolites in the silk glands; citrulline, shikimic acid, linoleic acid and other substances were upregulated. Citrulline and shikimic acid are related to the tricarboxylic acid cycle (TCA) and glycolytic pathway (EMP), respectively. In addition, in the choline metabolism in cancer pathway, phosphoinositide 3-kinase (PI3K) was increased. The activation of AKT (protein kinase B) can occur by PI3K-dependent and PI3K-independent pathways (Bhaskar and Hay 2007). AKT activation can increase the intracellular ATP level by 2- to 3-fold. At the same time, studies have shown that AKT can regulate the rate of EMP and aerobic oxidation in cells (Nogueira et al. 2008). In addition, AKT can indirectly promote oxidative phosphorylation by increasing the substrates or products of EMP, such as ADP, NADH and pyruvate, and increasing the flux of TCA and oxidative phosphorylation (Zhang et al. 2006). The silk gland cells are filled with rough endoplasmic reticulum, which provides a place for the rapid synthesis of silk protein in large quantities. The results of transmission electron microscopy can also verify this phenomenon. This suggests that after S. frugiperda feeds on azadirachtin for a short time, the insect is stimulated to produce an emergency response that will mobilise energy for the production of silk. After 72 h, the S. frugiperda silk gland was damaged, affecting spinning behaviour, and the spinning rate decreased.
It was also found that a large amount of amino acids, such as histidine, glycine, and leucine, were downregulated at the same time point. Studies have reported that the main component of insect silk is amino acids. Silk fibroin is a natural biological macromolecule composed of 19 amino acids. The main amino acids in silk fibroin are alanine, glycine, serine and tyrosine (Lucas 1966; Takahashi et al. 1999). The downregulation of amino acids may affect the quality of silk. As a result, spinning behaviour is affected, the quality of the silk worsens, and the phenomenon of sol breakage occurs.
S. frugiperda larvae will spread to the tip of the leaf in large numbers after hatching and fall from the edge under squeezing or collision. The larvae hang in the air from silk, and some larvae crawl up to the leaf along the silk, while others drift to surrounding plants with the help of the silk. In the presence of wind, they can float farther to increase the spread of newly hatched larvae. When the silk gland is diseased, the synthesis of silk fibroin energy in the silk gland is disturbed, and the quality of the silk is compromised. When the strength and length of the silk are weakened, the migration of the insect's hanging silk may be restricted. The formation of silk is closely related to the development of silk glands and the synthesis of silk protein. Understanding how the mechanism of silk gland development and the regulation of silk protein synthesis affect the spinning behaviour of insects is of great significance to the control of silk spitting insects.
In this study, we examined the effect of azadirachtin on the silk spitting of S. frugiperda by investigating the silk, silk gland and silk gland metabolome. When S. frugiperda fed on azadirachtin, its silk gland protein aggregation decreased, and pathological changes occurred. After 48 h, although substances related to energy metabolism in the silk gland increased, thus providing energy for silk synthesis, the downregulation of amino acids and other substances led to limited raw material for silk synthesis, affecting the quality of silk of S. frugiperda. Azadirachtin also inhibited the development of the silk glands, further affecting the spinning behaviour of S. frugiperda.
Acknowledgements
This research was supported by the Modern agricultural industrial technology System of Guangdong Province (The task of Innovation team building of key generic technologies in agricultural resources and environment) (2021KJ118). Guangzhou Science and Technology Planning Project (202102080120).
Ethics declarations
Conflict of interest
The authors declare no competing interests.
Authors’ contributions
Conceptualization, Formal analysis, Investigation, Writing-original draft: Weihua Zhao, Methodology: Peiru Luo, Cuiyi Ye, Validation: Shigang Shen, Writing-review & editing: Deqiang Qin, Investigation, Visualization: Qun Zheng, Writing-review & editing, Supervision: Hanhong Xu. Formal analysis, Resources: Suqing Huang, Dongmei Cheng, Conceptualization, Funding acquisition, Writing-review & editing, Supervision, Project administration: Zhixiang Zhang.
Author information
Affiliations
Key Laboratory of Natural Pesticide and Chemical Biology, Ministry of Education, South China Agricultural University, Guangzhou 510642, China.
Weihua Zhao, Qun Zheng, Deqiang Qin, Peiru Luo, Cuiyi Ye, Shigang Shen, Hanhong Xu*, Zhixiang Zhang*.
Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China. Dongmei Cheng, Suqing Huang.
Corresponding authors
Correspondence to Hanhong Xu or Zhixiang Zhang.
- Asakura T, Ogawa T, Naito A, and Williamson M P. 2020. Chain-folded lamellar structure and dynamics of the crystalline fraction of Bombyx mori silk fibroin and of (Ala-Gly-Ser-Gly-Ala-Gly)n model peptides. Int J Biol Macromol 164: 3974-3983. https://doi.org10.1016/j.ijbiomac.2020.08.220.
- Berger A. 1989. Ballooning activity of Chilo partellus larvae in relation to size of mother, egg batches, eggs and larvae and age of mother. Entomol Exp Appl 50: 125-132.
- Bhaskar P T, and Hay N. 2007. The two TORCs and Akt. Dev Cell 12: 487-502. https://doi.org10.1016/j.devcel.2007.03.020.
- Fang P, and Guo M. 2017. Structural characterization of human aminoacyl-tRNA synthetases for translational and nontranslational functions. Methods 113: 83-90. https://doi.org10.1016/j.ymeth.2016.11.014.
- Fedi R, Urovec M, and Sehnal F. 2003. The silk of lepidoptera. Journal of Sericultural Science of Japan 71: 1-15.
- Kumar J, Shakil N A, Singh M K, Singh M K, Pandey A, and Pandey R P. 2010. Development of controlled release formulations of azadirachtin-A employing poly (ethylene glycol) based amphiphilic copolymers. J Environ Sci Health B 45: 310-314. https://doi.org10.1080/03601231003704457.
- Li B, Sun Q, Yu X, Xie Y, Hong J, Zhao X, Sang X, Shen W, and Hong F. 2015. Molecular mechanisms of silk gland damage caused by phoxim exposure and protection of phoxim-induced damage by cerium chloride inBombyx mori. Environ Toxicol 30: 1102-1111. https://doi.org10.1002/tox.21983.
- Lin S, Li S, Liu Z, Zhang L, Wu H, Cheng D, and Zhang Z. 2021. Using azadirachtin to transform Spodoptera frugiperda from pest to natural enemy. Toxins 13: 541. https://doi.org10.3390/toxins13080541.
- Liu H, Lan T, Fang D, Gui F, and Liu X. 2019. Chromosome level draft genomes of the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), an alien invasive pest in China.
- Lucas F. 1966. Cystine content of silk fibroin (Bombyx mori). Nature 210: 952-953.
- Miranda M A F M, Matos A P, Volante A C, Cunha G O S, and Gualtieri S C J. 2022. Insecticidal activity from leaves and sesquiterpene lactones of Tithonia diversifolia (Helms.) a. Gray (Asteraceae) on Spodoptera frugiperda (Lepidoptera: Noctuidae). S Afr J Bot 144: 377-379. https://doi.org10.1016/j.sajb.2021.09.002.
- Mortimer B, Holland C, and Vollrath F. 2013. Forced reeling of Bombyx mori silk: separating behavior and processing conditions. Biomacromolecules 14: 3653-3659. https://doi.org10.1021/bm401013k.
- Nogueira V, Park Y, Chen C, Xu P, Chen M, Tonic I, Unterman T, and Hay N. 2008. Akt determines replicative senescence and oxidative or oncogenic premature senescence and sensitizes cells to oxidative apoptosis. Cancer Cell 14: 458-470. https://doi.org10.1016/j.ccr.2008.11.003.
- Paredes-Sánchez F A, Rivera G, Bocanegra-García V, Martínez-Padrón H Y, Berrones-Morales M, Niño-García N, and Herrera-Mayorga V. 2021. Advances in control strategies against Spodoptera frugiperda. A Review. Molecules 26: 5587. https://doi.org10.3390/molecules26185587.
- Pashley D P. 1986. Host-associated genetic differentiation in fall armyworm (Lepidoptera: Noctuidae): A sibling species complex? Ann.entomol.soc.am898-904.
- Qian W, Yang Y, Li Z, Wu Y, He X, Li H, and Cheng D. 2021. Enhanced myc expression in silkworm silk gland promotes DNA replication and silk production. Insects 12. https://doi.org10.3390/insects12040361.
- Qin D, Zhou Y, Zhang P, Liu B, Zheng Q, and Zhang Z. 2021. Azadirachtin downregulates the expression of the CREB gene and protein in the brain and directly or indirectly affects the cognitive behavior of the Spodoptera litura fourth-instar larvae. Pest Manag Sci 77: 1873-1885. https://doi.org10.1002/ps.6212.
- Roden D B. 1993. Laddering: Climbing behavior of the gypsy moth (Lepidoptera: Lymantriidae). Ann Entomol Soc Am379-383.
- Santorum M, Costa R M, Dos R G, and Carvalho D S D. 2020. Novaluron impairs the silk gland and productive performance of silkworm Bombyx mori (Lepidoptera: Bombycidae) larvae. Chemosphere 239: 124697. https://doi.org10.1016/j.chemosphere.2019.124697.
- Schmutterer H. 1990. Properties and potential of natural pesticides from the neem tree, azadirachta indica. Annu Rev Entomol 35: 271-297. https://doi.org10.1146/annurev.en.35.010190.001415.
- Sehnal F, and Akai H. 1990. Insect silk glands: Their types, development and function, and effects of environmental factors and morphogenetic hormones on them. International Journal of Insect Morphology and Embryology 19: 79-132. https://doi.orghttps://doi.org/10.1016/0020-7322(90)90022-H.
- Sen K, and Babu K M. 2004. Studies on Indian silk. I. Macrocharacterization and analysis of amino acid composition. J Appl Polym Sci 92: 1080-1097. https://doi.org10.1002/app.13609.
- Shi Y, Lin G, Fu X, Keller M, Smagghe G, and Liu T. 2020. Cocoon-Spinning behavior and 20-Hydroxyecdysone regulation of fibroin genes in plutella xylostella. Front Physiol 11. https://doi.org10.3389/fphys.2020.574800.
- Sisay B, Tefera T, Wakgari M, Ayalew G, and Mendesil E. 2019. The efficacy of selected synthetic insecticides and botanicals against fall armyworm, Spodoptera frugiperda, in Maize. Insects 10: 45. https://doi.org10.3390/insects10020045.
- Su H, Cheng Y, Wang Z, Li Z, Stanley D, and Yang Y. 2015. Silk gland gene expression during larval-pupal transition in the cotton leaf roller Sylepta derogata (Lepidoptera: Pyralidae). Plos One 10: e136868. https://doi.org10.1371/journal.pone.0136868.
- Sutherland T D, Young J H, Weisman S, Hayashi C Y, and Merritt D J. 2010. Insect silk: One name, many materials. Annu Rev Entomol 55: 171-188. https://doi.org10.1146/annurev-ento-112408-085401.
- Takahashi Y, Gehoh M, and Yuzuriha K. 1999. Structure refinement and diffuse streak scattering of silk (Bombyx mori). Int J Biol Macromol 24: 127-138. https://doi.org10.1016/s0141-8130(98)00080-4.
- Takei F, Oyama F, Kimura K I, Hyodo A, and Shimura M K. 1984. Reduced level of secretion and absence of subunit combination for the fibroin synthesized by a mutant silkworm, Nd (2). J Cell Biol 99: 2005-2010.
- Wang X, Li Y, Liu Q, Chen Q, Xia Q, and Zhao P. 2017. In vivo effects of metal ions on conformation and mechanical performance of silkworm silks. Biochimica et biophysica acta. General subjects 1861: 567-576. https://doi.org10.1016/j.bbagen.2016.11.025.
- Xia Q, Li S, and Feng Q. 2014. Advances in silkworm studies accelerated by the genome sequencing of bombyx mori. Annu Rev Entomol 59: 513-536. https://doi.org10.1146/annurev-ento-011613-161940.
- Zhang W, Patil S, Chauhan B, Guo S, Powell D R, Le J, Klotsas A, Matika R, Xiao X, Franks R, Heidenreich K A, Sajan M P, Farese R V, Stolz D B, Tso P, Koo S, Montminy M, and Unterman T G. 2006. FoxO1 regulates multiple metabolic pathways in the liver. J Biol Chem 281: 10105-10117. https://doi.org10.1074/jbc.M600272200.
