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Locusts exhibit remarkable density-dependent phenotype (phase) changes from the solitary to the gregarious, making them one of the most destructive agricultural pests. This phenotype polyphenism arises from a single genome and diverse transcriptomes in different conditions. Here we report a de novo transcriptome for the migratory locust and a comprehensive, representative core gene set. We carried out assembly of 21.5 Gb Illumina reads, generated 72,977 transcripts with N50 2,275 bp and identified 11,490 locust protein-coding genes. Comparative genomics analysis with eight other sequenced insects was carried out to identify the genomic divergence between hemimetabolous and holometabolous insects for the first time and 18 genes relevant to development was found. We further utilized the quantitative feature of RNA-seq to measure and compare gene expression among libraries. We first discovered how divergence in gene expression between two phases progresses as locusts develop and identified 242 transcripts as candidates for phase marker genes. Together with the detailed analysis of deep sequencing data of the 4(th) instar, we discovered a phase-dependent divergence of biological investment in the molecular level. Solitary locusts have higher activity in biosynthetic pathways while gregarious locusts show higher activity in environmental interaction, in which genes and pathways associated with regulation of neurotransmitter activities, such as neurotransmitter receptors, synthetase, transporters, and GPCR signaling pathways, are strongly involved. Our study, as the largest de novo transcriptome to date, with optimization of sequencing and assembly strategy, can further facilitate the application of de novo transcriptome. The locust transcriptome enriches genetic resources for hemimetabolous insects and our understanding of the origin of insect metamorphosis. Most importantly, we identified genes and pathways that might be involved in locust development and phase change, and may thus benefit pest management.

The intermediate principal stress (σ2 ) effect is a mechanical property inherent in many rock and soil materials. However, the effect of σ2 is often ignored in slope stability analyses, and its impact on slope stability is seldom investigated. The primary purpose of this study is to thoroughly investigate the impact of the σ2 effect on slope stability via numerical method. A detailed numerical analysis using the Finite Difference Code Fast Lagrangian Analysis of Continua (FLAC) and Unified Strength Theory (UST) is conducted. The numerical analysis evaluates the values of the Factor of Safety (FOS) for two types of slopes (plane strain and axisymmetric) using the Strength Reduction Method (SRM), and the impact of the σ2 effect on slope stability is analysed. The study found that the influence of the σ2 effect on slope stability is not sensitive to the values of friction angle φ, cohesion c, and slope height H, but increases with increasing slope angle σ values. Furthermore, the stability of the plane strain slope is more affected by the σ2 effect than the axisymmetric slope. The impact of the σ2 effect on the footing capacity and slope stability were compared, and the impact of the σ2 effect on slope stability is significantly lower than its effect on the bearing capacity of footings. The innovation of this paper is to systematically analyse the effect of σ2 on slope with different geometric shapes and soil parameters and reveal the inherent characteristics of σ2 effect on the stability of soil slope.

The method of two-phase flow is used to analyze the three-dimensional debris flow field via the theory of computational fluid dynamics (CFD). The theory of computational fluid dynamics and finite volume method is introduced briefly, and the rheological characteristic of non-Newtonian fluid is illuminated. The three-dimensional topography model of Niwan gully was established, and the three-dimensional debris flow field was analyzed. The values and distributions of velocity and pressure field of the debris flow have been obtained; the relationship between the shear strain rate, viscosity, and velocity was analyzed. The results suggest that it is more accurate to catch the free surface of debris flow using the method of two-phase flow. The sediment area of the Niwan gully debris flow can be estimated quickly, and it may have significance for the engineering prevention of debris flow disasters.

Behavioral plasticity is the most striking trait in locust phase transition. However, the genetic basis for behavioral plasticity in locusts is largely unknown. To unravel the molecular mechanisms underlying the behavioral phase change in the migratory locust Locusta migratoria, the gene expression patterns over the time courses of solitarization and gregarization were compared by oligonucleotide microarray analysis. Data analysis revealed that several gene categories relevant to peripheral olfactory perception are strongly regulated in a total of 1,444 differentially expressed genes during both time courses. Among these candidate genes, several CSP (chemosensory protein) genes and one takeout gene, LmigTO1, showed higher expression in gregarious and solitarious locusts, respectively, and displayed opposite expression trends during solitarization and gregarization. qRT-PCR experiments revealed that most CSP members and LmigTO1 exhibited antenna-rich expressions. RNA interference combined with olfactory behavioral experiments confirmed that the CSP gene family and one takeout gene, LmigTO1, are involved in the shift from repulsion to attraction between individuals during gregarization and in the reverse transition during solitarization. These findings suggest that the response to locust-emitted olfactory cues regulated by CSP and takeout genes is involved in the behavioral phase change in the migratory locust and provide a previously undescribed molecular mechanism linked to the formation of locust aggregations.

The migratory locust, Locusta migratoria, shows a striking phenotypic plasticity. It transitions between solitary and gregarious phases in response to population density changes. However, the molecular mechanism underlying the phase-dependent behavior changes remains elusive. Here we report a genome-wide gene expression profiling of gregarious and solitary nymphs at each stadium of the migratory locust, and we identified the most differentially expressed genes in the fourth stadium of the two phases. Bioinformatics analysis indicated that the catecholamine metabolic pathway was the most significant pathway up-regulated in the gregarious phase. We found pale, henna, and vat1, involved in dopamine biosynthesis and synaptic release, were critical target genes related to behavioral phase changes in the locusts. The roles of these genes in mediating behavioral changes in the gregarious individuals were confirmed by RNAi and pharmacological intervention. A single injection of dopamine or its agonist initiated gregarious behavior. Moreover, continuous and multiple injections of a dopamine agonist coupled with crowding resulted in more pronounced gregarious behavior. Our study thus provides insights into the relationships between genes and behavior in phase transition of this important pest species.

Aggregative and solitary behaviors are universal phenomena in animals. Interestingly, locusts ( Locusta migratoria ) can reversibly transit their behavior between gregarious and solitary phase through conspecific attraction and repulsion. However, the regulatory mechanism of neurotransmitters underlying attraction and repulsion among locusts remains unknown. In this study, we found gregarious and solitary locusts were attracted or repulsed respectively by gregarious volatiles. Solitary locusts can transform their preference for gregarious volatiles during crowding, whereas gregarious locusts avoided their volatiles during isolation. During crowding and isolation, the activities of octopamine and tyramine signalings were respectively correlated with attraction- and repulsion-response to gregarious volatiles. RNA interference verified that octopamine receptor α (OARα) signaling in gregarious locusts controlled attraction-response, whereas in solitary ones, tyramine receptor (TAR) signaling mediated repulsion-response. Moreover, the activation of OARα signaling in solitary locusts caused the behavioral shift from repulsion to attraction. Enhancement of TAR signaling in gregarious locusts resulted in the behavioral shift from attraction to repulsion. The olfactory preference of gregarious and solitary locusts co-injected by these two monoamines displayed the same tendency as the olfactory perception in crowding and isolation, respectively. Thus, the invertebrate-specific octopamine-OARα and tyramine-TAR signalings respectively mediate attractive and repulsive behavior in behavioral plasticity in locusts.

The migratory locust, Locusta migratoria, shows remarkable phenotypic plasticity at behavioral, physiological, and morphological levels in response to fluctuation in population density. Our previous studies demonstrated that dopamine (DA) and the genes in the dopamine metabolic pathway mediate phase change in Locusta. However, the functions of different dopamine receptors in modulating locust phase change have not been fully explored. In the present study, DA concentration in the brain increased during crowding and decreased during isolation. The expression level of dopamine receptor 1 (Dop1) increased from 1 to 4 h of crowding, but remained unchanged during isolation. Injection of Dop1 agonist SKF38393 into the brains of solitary locusts promoted gregarization, induced conspecific attraction-response and increased locomotion. RNAi knockdown of Dop1 and injection of antagonist SCH23390 in gregarious locusts induced solitary behavior, promoted the shift to repulsion-response and reduced locomotion. By contrast, the expression level of dopamine receptor 2 (Dop2) gradually increased during isolation, but remained stable during crowding. During the isolation of gregarious locusts, injection of Dop2 antagonist S(-)-sulpiride or RNAi knockdown of Dop2 inhibited solitarization, maintained conspecific attraction-response and increased locomotion; by comparison, the isolated controls displayed conspecific repulsion-response and weaker motility. Activation of Dop2 in solitary locusts through injection of agonist, R(-)-TNPA, did not affect their behavioral state. Thus, DA-Dop1 signaling in the brain of Locusta induced the gregariousness, whereas DA-Dop2 signaling mediated the solitariness. Our study demonstrated that Dop1 and Dop2 modulated locust phase change in two different directions. Further investigation of Locusta Dop1 and Dop2 functions in modulating phase change will improve our understanding of the molecular mechanism underlying phenotypic plasticity in locusts.

Seepage flow is one of the primary factors that trigger slopes and landslides’ failure. In this study, the slope stability under saturated or unsaturated conditions is analyzed. The influence of a complex stress state on the slope stability with the saturated or unsaturated seepage flow is proposed in this paper. Firstly, an elastoplastic constituted model for the soil under a complex stress state is established and as a user subroutine of the finite element method code of FLAC. Secondly, the 2D and 3D problems of slope stability influenced by the saturated or unsaturated seepage flow are analyzed via the finite difference method with the influence of the complex stress state. Finally, the influence of the intermediate principal stress and the saturated or unsaturated seepage flow on the slope stability is analyzed in this study.

Dopamine receptor 1 (Dop1) mediates locust attraction behaviors, however, the mechanism by which Dop1 modulates this process remains unknown to date. Here, we identify differentially expressed small RNAs associated with locust olfactory attraction after activating and inhibiting Dop1. Small RNA transcriptome analysis and qPCR validation reveal that Dop1 activation and inhibition downregulates and upregulates microRNA-9a (miR-9a) expression, respectively. miR-9a knockdown in solitarious locusts increases their attraction to gregarious volatiles, whereas miR-9a overexpression in gregarious locusts reduces olfactory attraction. Moreover, miR-9a directly targets adenylyl cyclase 2 ( ac2 ), causing its downregulation at the mRNA and protein levels. ac2 responds to Dop1 and mediates locust olfactory attraction. Mechanistically, Dop1 inhibits miR-9a expression through inducing the dissociation of La protein from pre-miR-9a and resulting in miR-9a maturation inhibition. Our results reveal a Dop1–miR-9a–AC2 circuit that modulates locust olfactory attraction underlying aggregation. This study suggests that miRNAs act as key messengers in the GPCR signaling. Migratory locusts shift between aggregating together during gregarious phases and living individually during solitary phases. Here, the authors find that the D1-like dopamine receptor regulates the olfactory attraction underlying this behavioral switch via microRNA-9a and adenylyl cyclase.

This study proposes a comprehensive matrix improvement and artificial planting greening technology with the ecological restoration and greening challenges posed by exposed coal gangue strata following the excavation of Karst mountainous highway slopes. By considering the properties of coal gangue, regional climate conditions, and vegetation characteristics, the proposed approach integrates spray modification, covering and sealing, and selective planting techniques. This method not only reduces construction costs but also effectively enhances the ecological restoration level of mountainous coal gangue slopes while improving the survival rate of green vegetation. Drawing from an actual project involving the excavation of exposed coal gangue on the slope of a highway under construction, a microbial water-retaining agent was sprayed to modify the surface coal gangue soil layer through microbial action. Subsequently, cement-mixed soil was applied to cover and seal the coal gangue layer. Finally, the greening of the coal gangue slope was achieved via carefully selected and manually planted vegetation. This research contributes to advancing the green ecological construction of transportation infrastructure in Karst mountainous regions and provides valuable references for similar projects.