【Background】Sphingolipids are the second major type of membrane lipids and mediate various biological processes as signal transducers, including cell growth, development, reproduction and apoptosis. Sphingolipid metabolism is tightly regulated by sphingolipid metabolizing enzymes to maintain the homeostasis of metabolism in vivo.aaaaa【Objective】The objectives of this study are to investigate the relative transcript levels of genes related to the sphingolipid metabolism pathway after silencing of the core components of microRNA (miRNA) biosynthesis pathway, NlAgo1, NlDicer1 and NlDrosha by RNA interference (RNAi), and analyze the differentially expressed miRNAs after silencing of serine palmitoyltransferase 1 (SPT1) and sphingomyelinase 4 (SMase4) gene combined with small RNA sequencing of Nilaparvata lugens, explore the role of miRNAs in the sphingolipid metabolism of N. lugens, and to provide a new molecular target for pest control.【Method】RNAi was performed with double stranded RNAs (dsRNAs) targeting NlAgo1, NlDicer1 and NlDrosha at 1 day post adult eclosion (1 PAE), respectively, and dsGFP was used as control. The ovaries at 5 PAE were dissected and β-actin was used as internal reference gene, the transcript levels of genes related to the sphingolipid metabolism pathway were detected by reverse-transcription quantitative PCR (qRT-PCR). miRNAs that may regulate the expression of NlSPT1 and NlSMase4 were predicated based on small RNA libraries combined with miRNA-target prediction software. Differentially expressed miRNAs after the silencing of NlSPT1 and NlSMase4 were identified and the target gene enrichment was analyzed by small RNA sequencing.【Result】RNAi-mediated silencing of NlAgo1, NlDicer1 or NlDrosha significantly up-regulated the expression of genes related to the sphingolipid metabolism pathway, including NlSPT1 and NlSMase4 in ovaries. Target gene prediction revealed 6 miRNAs and 13 miRNAs that could bind NlSPT1 and NlSMase4. The target genes of differentially expressed miRNAs that silencing NlSPT1 and NlSMase4 were significantly enriched in biological processes, including nuclear and protein binding, as well as metabolic pathways such as endocytosis, endoplasmic reticulum processing, MAPK signaling pathway, TOR signaling pathway, apoptosis, and lipid metabolism.【Conclusion】NlAgo1, NlDicer1, and NlDrosha-dependent miRNAs affect sphingolipid metabolism by influencing the expression of genes encoding sphingolipid metabolizing enzymes. The silencing of NlSPT1 and NlSMase4 induced changes in miRNA expression levels in N. lugens ovaries. These research results can provide a theoretical basis for pest control based on sphingolipid metabolism genes.
【Objective】Climate warming can affect the occurrence and damage caused by wheat aphids. Rhopalosiphum padi and Sitobion avenae as the main pests of wheat in the Huang-Huai-Hai region of China, their population development and reproduction are affected by warming. This study aims to investigate whether climate warming will change the wheat rhizosphere microorganisms, which would indirectly affect the development and reproduction of R. padi and S. avenae.【Method】At the Yuanyang experimental station in Henan Province, infrared radiation heaters were hung to simulate a temperature increased by 2 ℃, and the number of wheat aphids occurring was investigated after the wheat returned to the greening stage. During the wheat jointing stage, rhizosphere microorganisms were collected and then brought to the laboratory to obtain the mixed microbial solution. The population dynamics and age-stage two-sex life table of two aphid species were tested by irrigating wheat with mixed solution. The mixture of rhizosphere microorganism was irrigated, and then aphids were inoculated. The number of aphids was recorded after 5 consecutive observations. For life table experiments, individual aphid of two wheat aphid species was fixed onto the 2nd leaf of wheat using ecological boxes, and the molting, instar and mortality of nymphal aphid were observed and recorded every day. At the same time, the reproduction and mortality of adult aphid were also recorded.【Result】Under different treatments, the population dynamics of R. padi and S. avenae were increasing continuously. With increasing investigation frequency, the increase of aphids gradually increased with irrigating the rhizosphere microorganisms of the elevated field compared with that at the ambient field. Rhizosphere microorganisms in the elevated field significantly increased the total mean number of R. padi and S. avenae, and compared with S. avenae, the increase of R. padi was greater, which increased by 4.49 times of S. avenae. The results of the population life table showed that the rhizosphere microorganisms in the elevated field significantly shortened the mean generation time, population doubling time, preadult duration, and oviposition duration of R. padi, while significantly increasing its intrinsic rate of increase, finite rate of increase and offspring. In addition, rhizosphere microorganisms in the elevated field significantly improved the survival rates of S. avenae at all developmental stages.【Conclusion】Warming promotes the growth, development, and reproduction of R. padi, enhances the survival rate of S. avenae, and accelerates the population growth of both aphid species, respectively, by affecting rhizosphere microorganisms, which may lead to changes in the migratory behavior of the aphids. These findings provide initial insights into the outbreak mechanism of wheat aphids under climate warming, and offer valuable references for predicting and assessing wheat aphid occurrences under future climate warming.
【Objective】This study aims to investigate the feeding metabolic characteristics and migration behavior of Spodoptera frugiperda on soybean and maize, as well as to clarify the feeding rules and potential damage risks of S. frugiperda in the soybean- maize strip intercropping.【Method】The host plants were Xudou 18 and Jiangyu 877, which were recommended for soybean-maize strip intercropping planting in Jiangsu Province. The effects of soybean leaves and maize leaves on feeding preference, growth, oviposition quantity, oviposition selectivity, digestive enzyme activity and digestive metabolism of S. frugiperda were determined by laboratory tests. Field inoculation experiment was conducted to investigate the migration distance and range of S. frugiperda over time under the “2+4” intercropping of maize and soybean, and the potential risk of damage was evaluated based on the migration dynamics.【Result】S. frugiperda exhibited a clear preference for feeding on maize leaves, with 63.89% of individuals selecting to feed on maize leaves, which was 1.77 times higher than the number of individuals that selected to feed on soybean leaves, and the difference was significant. S. frugiperda could complete its life cycle by feeding on both soybean leaves and maize leaves, but the larval development period of those feeding on maize leaves was 14.82 d, which was 2.54 d shorter than those feeding on soybean leaves. The single female fecundity of S. frugiperda feeding on maize leaves was 679.50 eggs, which was significantly increased by 26.58% compared to feeding on soybean leaves. Adult females preferred to oviposit on maize leaves, with the average egg mass number and single female oviposition of 5.67 masses and 521.67 eggs, respectively, which were 1.70 and 2.04 times higher than those on soybean, and the differences were significant. The lipase activity of S. frugiperda feeding on soybean leaves was 9.84 U·g-1, significantly higher than that of those feeding on maize leaves (6.47 U·g-1), while there was no significant difference in protease and amylase activities between the two. The approximate digestibility of S. frugiperda feeding on soybean leaves was 63.40%, which was significantly lower than that of those feeding on maize leaves (69.26%). However, there was no significant difference in food utilization efficiency, food conversion efficiency, and relative growth rate between the two. Field investigations after egg mass inoculation revealed that in the “2+4” strip intercropping pattern of maize and soybean, S. frugiperda primarily infested the maize plants, exhibiting “vertical migration” within the maize rows, and did not spread to the neighboring soybean plants.【Conclusion】S. frugiperda exhibited distinct differences in feeding adaptation and oviposition preference between soybean and maize, displaying a stronger preference and utilization ability for maize compared to soybean. Under the “2+4” strip planting pattern of maize and soybean, S. frugiperda primarily inflicted damage on maize. Therefore, in practical agricultural production, it is crucial to enhance monitoring and control measures for S. frugiperda, particularly during the critical growth stages of maize, to mitigate the risk of damage.
【Objective】It has been reported that Nilaparvata lugens (brown planthopper, BPH) exhibits a preference of endangering rice plants infested by Chilo suppressalis (striped stem borer, SSB). However, it remains unclear whether this phenomenon is influenced by the developmental stage of N. lugens and the rice variety. This study aims to investigate the effects of rice varieties and developmental stages of N. lugens on the preference for C. suppressalis-infested rice plants, as well as how volatiles mediate this behavior, so as to provide a scientific basis for formulating green pest control strategies.【Method】Through indoor choice experiments, the attraction of different developmental stages of N. lugens (including 3rd-4th instar nymphs, newly emerged females, gravid females) to nine rice varieties, including Zhongzheyou 8, both damaged and undamaged by C. suppressalis, was observed. Based on these observations, representative varieties showing significant differences in attraction were selected for further analysis. RT-qPCR was used to detect changes in the expression of volatile synthesis-related genes in three rice varieties (Zhongzheyou 8, 9311, and Minghui 63) following pest infested.【Result】Among the nine rice varieties, different developmental stages of N. lugens consistently showed a preference for rice plants infested by C. suppressalis, although this preference varied among rice varieties. For instance, newly emerged female N. lugens exhibited a significantly higher preference for Minghui 63 compared to Yongyou 538. Gene expression analysis revealed a significant increase in the expression levels of volatile synthesis-related genes OsCAS, OsLIS, OsHPL3, and OsRCI-1 in response to C. suppressalis infestation. However, when different developmental stages of N. lugens were co-infested with C. suppressalis, the expression levels of these genes could either increase or decrease compared to plants infested only by C. suppressalis, with specific effects depending on the developmental stage of N. lugens.【Conclusion】The preference of N. lugens for rice plants infested by C. suppressalis was commonly observed across the nine tested rice varieties. However, significant differences in the degree of preference were noted among different developmental stages of N. lugens across these varieties. Notably, variations in preference among developmental stages of N. lugens were primarily observed in the selection of rice varieties Yongyou 538, Zhongzheyou 8, and Minghui 63 by newly emerged female. Infestation only by C. suppressalis or in conjunction with N. lugens resulted in increased expression levels of the genes OsCAS, OsLIS, OsHPL3, and OsRCI-1, indicating that pest infestation in rice plants can regulate the synthesis of rice volatiles, thereby influencing the host selection behavior of N. lugens.
【Objective】The Toll receptor is one of the key effector factors in the Toll signaling pathway of the innate immune system in insects. This article aims to identify the Toll receptor genes of three types of rice planthoppers (Nilaparvata lugens, Sogatella furcifera, and Laodelphax striatellus), explore the potential functions of the Toll receptor in these three species, and investigate the interspecies differences, so as to provide a theoretical basis for the study of the immune development of rice planthoppers and for the control and prevention of these pests.【Method】Bioinformatics methods were used to identify Toll receptor genes from the genomes of three species of rice planthoppers, and the gene structure and characteristics, physicochemical properties and structural domains of the encoded proteins, chromosome localization and phylogenetic evolutionary relationships were analyzed. Artificial intelligence software AlphaFold 3 was used to predict the three-dimensional structure of Toll receptors and compare it with the known structures and functions of Toll receptors from other species to predict their potential functions and interspecific functional differentiation. Transcriptome data were used to quantitatively analyze the expressions of Toll receptor genes in different tissues and at different developmental stages.【Result】A total of 6, 7, and 6 Toll receptor genes were identified in the genomes of N. lugens, S. furcifera, and L. striatellus, respectively, all of which are distributed on chromosomes 1, 4, and 7, with a clear distribution pattern. The Toll gene family in the three species of rice planthoppers is distributed with one gene on chromosomes 1 and 4, and the rest on chromosome 7. The coding sequence lengths of the Toll receptor genes in the three species of rice planthoppers range from 2 676 to 4 158 bp, with the number of exons ranging from 1 to 7, and the encoded protein sequence lengths range from 891 to 1 385 aa, with molecular weights ranging from 103.31 to 158.25 kDa and theoretical isoelectric points ranging from 5.42 to 6.54. Phylogenetic development analysis showed that the Toll receptor gene family of the three species of rice planthoppers can be divided into six subfamilies, which are homologous to the Toll, Toll6, Toll7, Tollo (Toll8), and Toll9 of other insects. The comparison analysis of the extracellular structures predicted by AlphaFold 3 with those of Toll receptors from other species showed that two Toll receptors in the Toll receptor gene family of S. furcifera were potentially related to virus interactions, one in the Toll receptor gene family of L. striatellus, and none in the Toll receptor gene family of N. lugens. Transcriptome quantitative results showed that the Toll receptor genes in the three species of rice planthoppers were expressed in different tissues and at different developmental stages, suggesting that they may have different functions and participate in different divisions of labor.【Conclusion】A total of 19 Toll receptor genes were identified in three species of rice planthoppers, and their related structures and functions were analyzed and predicted. The study revealed potential differences in the roles played by Toll receptors in the development and immune response, particularly in virus immunity, within the insect body among these three species of rice planthoppers.
【Objective】At present, crop pests are more adaptable to high relative humidity. Aquaporin (AQP) is a membrane protein that is necessary for insects to maintain water balance in the body. The objectives of this study are to screen two McAQP sequence structures by transcriptome sequencing through high relative humidity stress, clarify the AQP characteristics of Megoura crassicauda and the expression changes in response to high relative humidity stress combined with real-time fluorescence quantitative PCR (qRT-PCR) verification, and to provided a theoretical basis for further exploring the gene function of AQP.【Method】The environmental relative humidity (RH) of 60%, 75% and 90% were set to cultivate M. crassicauda. The growth and development were observed, the relative expression of genes and the content of related substances in the body were detected. Based on two McAQP sequences (named as McAQP X1 and McAQP X2, respectively) obtained from comparative transcriptome sequencing of M. crassicauda, the physicochemical property, sequence structure, and the homology with other insects were analyzed by bioinformatics methods. Finally, qRT-PCR was used to determine the relative expression of AQP X1, AQP X2, Vg and VgR under long-term stable high relative humidity stress and 24 h emergency high relative humidity stress.【Result】Compared with RH 60% and RH 75%, the fecundity of M. crassicauda under RH 90% was significantly reduced, but there was no significant difference in development duration and survival rate. With the increase of relative humidity, the water content of M. crassicauda decreased, and the special phenotype phenomena such as body color change and long wing appeared. The molecular weights of McAQP X1 and McAQP X2 are 33.89 and 28.94 kDa, the theoretical isoelectric points are 5.36 and 5.32, and the protein lengths are 308 and 272 aa, respectively. On the multistage structure, McAQP is arranged by six long alpha helices via counterclockwise rotation to form a barrel channel, whereas four monomers form a tetramer to exercise function. The relative expression of McAQPs quantified by qRT-PCR showed that both McAQP X1 and McAQP X2 were up-regulated with increasing relative humidity, which was generally consistent with the transcriptome sequencing results. Meanwhile, under long-term stable high humidity stress, both Vg and VgR were up-regulated under RH 75% and down-regulated under RH 90%. Under 24 h emergency high humidity stress, Vg expression level was down-regulated with increasing humidity, while VgR was up-regulated under RH 90%.【Conclusion】High humidity environment affects the reproduction, water content and body color of M. crassicauda. The aquaporin sequence structure in subfamily II is relatively conservative, without strong species-specific differentiation. NPA site is important for the function of aquaporin, and the asparagine residue plays a structural role for water molecules through the central channel. It is speculated that the expression change of AQPs may be an important means for M. crassicauda to cope with humidity changes.
【Objective】Ostrinia furnacalis is one of the most destructive migratory Lepidopteran pests, which seriously threatens the safety of maize production in China. The population dynamics and migration status monitored by ground light-trap and searchlight trap were compared and evaluated to provide a scientific basis for migration monitoring and early warning and control of O. furnacalis.【Method】Ground light-trap and searchlight trap were used to monitor the population of O. furnacalis in Yantai, Shandong from 2019 to 2023. Daily collection and statistics were carried out on the number of O. furnacalis from April 1 to October 31 each year. The population dynamics of O. furnacalis were analyzed by drawing monitoring curves. The up-lighting pattern of O. furnacalis was analyzed based on the percentage of daily trapped number to annual trapped number by ground light-trap and searchlight trap. The migration status of O. furnacalis was analyzed based on the phenomenon of “sudden increase and decrease” of migration insect populations and the ratio of the number of insects trapped by searchlight trap and ground light-trap.【Result】The number of O. furnacalis varied in different years and months, and the number trapped by searchlight trap was higher than that of ground light-trap. Pearson correlation analysis showed that there was no correlation between the annual total number of O. furnacalis trapped by ground light-trap and searchlight trap. The population dynamics of O. furnacalis monitored by ground light-trap and searchlight trap were basically consistent, but the peak of O. furnacalis trapped by searchlight trap was obvious, the start time was earlier than that by ground light-trap, and ended later. The up-lighting pattern of O. furnacalis was consistent between ground light-trap and searchlight trap, containing only three types: peak days, general occurrence days and non-occurrence days, and the peak day showed two peak stages with mid-July as the dividing point. O. furnacalis had two migration stages, with a low population and short duration from late May to late June, and a high population and long duration from late July to mid-September.【Conclusion】The population dynamics of O. furnacalis under ground light-trap and searchlight trap are consistent, indicating both methods are reliable for monitoring the dynamics of O. furnacalis. However, searchlight trap has more advantages in monitoring the early migration status of O. furnacalis because of its large number of insects, obvious peak of insects, early first peak appearance and long peak period. Searchlight trap can be used for timely monitoring the occurrence of O. furnacalis to prevent pest. The up-lighting pattern of O. furnacalis trapped by ground light-trap and searchlight trap is consistent with two peaks, so both traps can be used for monitoring. O. furnacalis migrates northward from late May to late June, and southward from late July to mid-September in Yantai. Therefore, monitoring and early warning and prevention can be strengthened in advance in the migration path to govern the migratory population of O. furnacalis.
【Objective】The objective of this study is to explore the vibration propagation laws of mating calls of the brown planthopper (BPH), Nilaparvata lugens, and to provide the theoretical basis and practical guidance for the development and optimization of novel techniques for physical pest control.【Method】Simulating a paddy field scenario, using the root mean square (RMS) as the measurement index of vibration intensity, the PDV-100 digital laser vibrometer was applied to test and analyze the propagation and attenuation characteristics of vibrations generated by different types of loudspeakers (as vibration sources) in water, air, and on rice plants. Based on the principle of substrate-borne vibration in insects, a steel needle point-touch method was used to play back female mating calls at varying intensities, which aimed to test the response rate of males during their mating active period and determine the range of vibration intensity they could perceive.【Result】When the vibration source was placed in water or air, the vibration intensities of the sinusoidal waves on rice plants decreased with increasing distance within the range of 10 to 500 cm. However, except for the position 10 cm from the vibration source, there was no significant difference in vibration intensity between the two modes at other positions (60-500 cm). At 60 cm, the intensity decreased by 84.87% in water and 73.08% in air compared to that at 10 cm. Furthermore, the application of higher-power directional loudspeakers revealed significantly extended propagation distances of sinusoidal wave signals in the air. Vibration sources with 20 and 30 W output power were attenuated by 87.27% at 15 m and 66.72% at 20 m, respectively. The vibration intensity on rice plants when playing back pre-recorded female and male courtship vibration signals showed no significant difference and increased with the signal strength of the vibration source, following an exponential function relationship. Additionally, the response rate of N. lugens males to female signals of different intensities showed significant differences. When the vibration velocity ranged from 782.2 to 835.9 μm·s-1, over 83% of male insects exhibited a calling response; however, when the vibration velocity was between 335.2 and 425.4 μm·s-1 or lower, fewer than 47% of males responded.【Conclusion】The disruptive vibrational signals can propagate to rice plants through the airborne pathway, with greater vibration source intensity resulting in farther propagation distances. The vibration conduction characteristics of rice plants are similar at different growth stages, but rice stems conduct vibrations more effectively than leaves. The results of response tests of N. lugens adults to different vibration intensities can serve as a basis for evaluating the effectiveness of disruptive vibrational signals in controlling N. lugens in the future.
