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Abstract Background Juvenile hormone (JH) is an insect-exclusive hormone involved in regulating diverse aspects of insect physiology, and the evolution of its diverse function is widely interesting. Studying embryogenesis in basal wingless insects is important to understand the functional evolution of JH; however, experimental studies in this regard are scarce. In this study, we conducted CRISPR/Cas9-mediated knockout (KO) of genes involved in JH biosynthesis and signaling cascades in the ametabolous firebrat, Thermobia domestica. Additionally, we investigated whether the primitive action of JH is conserved in the hemimetabolous cricket, Gryllus bimaculatus. Results We observed that KO of JHAMT, CYP15A1, Met, and Kr-h1 resulted in embryonic lethality in T. domestica. Deprivation of JH or JH signaling arrested the progression of extraembryonic fluid resorption after dorsal closure and hatching, which is consistent with the gene expression pattern showing high Kr-h1 expression in the late embryos of T. domestica. The embryos deficient in JH signaling displayed wrinkled and weak legs. Comparative transcriptome analysis revealed that JH signaling promotes embryonic leg maturation through inducing energy supply and muscle activity, as validated by transmission electron microscopy (TEM). In addition, JH signaling exhibited similar embryonic effects in G. bimaculatus. Conclusions This study reveals the indispensable role of JH signaling in facilitating the maturation of terminal tissues during late embryogenesis, as demonstrated by the regulation of leg development, in ametabolous and hemimetabolous insects. These findings further indicate that the embryonic functions of JH evolved earlier than its anti-metamorphic functions during postembryonic development.

The green peach aphid, Myzus persicae (Sulzer), is a significant global pest in horticultural and field crops. Afidopyropen is a novel systemic insecticide with high efficacy against sucking pests, and it is suitable for the management of M. persicae. However, the persistent toxicity and dissipation dynamics of afidopyropen in vegetables remain unknown. In this study, we determined the residual activity and dissipation dynamics of afidopyropen against M. persicae on cabbage and chili. The data showed that the toxicity of afidopyropen against M. persicae lasted more than 30 days; the corrected mortality was greater than 80% 10 days after application and was 50–60% 30 days post-application. The afidopyropen residues on cabbage and chili plants were quantified using ultrahigh-pressure liquid chromatography–tandem mass spectrometry. The dissipation half-lives of afidopyropen on cabbage and chili plants ranged from 1.45 to 2.34 days and 3.98–5.98 days at different recommended dosages, respectively. Our findings provide valuable data for the maximum residue limits of afidopyropen on vegetables and will help growers determine the frequency and timing of its application on cabbage and chili.

The green peach aphid, Myzus persicae (Sulzer) is a generalist pest of various host plants, whose feeding preference and growth performance mainly depends on the quantity and quality of nutrients and defensive metabolites in host plants. Here, we studied the preference and performance of M. persicae on three major Brassicaceae vegetables in China and measured nutrient (amino acids) and defensive metabolites (glucosinolates) in these plants. We found that M. persicae preferred and performed better on Chinese cabbage than cabbage and radish, which may be due to the relatively higher concentration of amino acids and lower levels of indole glucosinolates in their leaves. The glucosinolates level in cabbage leaves was ten times higher than the other two plants, while the amino acid concentration in radish was only half of the cabbage or Chinese cabbage. The higher concentration of indole glucosinolates in cabbage and lower levels of amino acids in radish may account for the poorer preference and growth of M. persicae on these two plants. These results suggest that both amino acids and glucosinolates in plants may play important roles in the preference and performance of M. persicae, which provide new knowledge for the cultivation and breeding of Brassicaceae vegetables.

Ecdysone-induced protein 93 (E93), known as the 'adult-specifier' transcription factor in insects, triggers metamorphosis in both hemimetabolous and holometabolous insects. Although E93 is conserved in ametabolous insects, its spatiotemporal expression and physiological function remain poorly understood. In this study, we first discover that, in the ametabolous firebrat Thermobia domestica, the previtellogenic ovary exhibits cyclically high E93 expression, and E93 mRNA is broadly distributed in previtellogenic ovarioles. E93 homozygous mutant females of T. domestica exhibit severe fecundity deficiency due to impaired previtellogenic development of the ovarian follicles, likely because E93 induces the expression of genes involved in ECM (extracellular matrix)-receptor interactions during previtellogenesis. Moreover, we reveal that in the hemimetabolous cockroach Blattella germanica, E93 similarly promotes previtellogenic ovarian development. In addition, E93 is also essential for vitellogenesis that is necessary to guarantee ovarian maturation and promotes the vitellogenesis-previtellogenesis switch in the fat body of adult female cockroaches. Our findings deepen the understanding of the roles of E93 in controlling reproduction in insects, and of E93 expression and functional evolution, which are proposed to have made crucial contributions to the origin of insect metamorphosis. [ABSTRACT FROM AUTHOR]