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BACKGROUND: Galeruca daurica has become a new pest on the Inner Mongolia grasslands since an abrupt outbreak in 2009 caused serious damage. As a pupa indicator during insect metamorphosis, the early response gene of the ecdysone signaling pathway, Broad‐Complex (Br‐C), plays a vital role in the growth and development of insects. MicroRNAs (miRNAs) are small non‐coding RNAs which mediate various biological activities, but it is unknown whether and how Br‐C is regulated by miRNAs. RESULTS: Temporal expression profiles revealed that miR‐285 and Br‐C basically displayed an opposite trend during larval–adult development, and Br‐C was sharply up‐regulated on the last day of final‐instar larvae while miR‐285 was significantly down‐regulated. Both dual‐luciferase reporter assay and miRNA–mRNA interaction assay indicated that miR‐285 interacts with the coding sequence of Br‐C and represses its expression. Not only overexpression but also downexpression of miR‐285 led to the failure of larval to pupal to adult metamorphosis. In addition, both overexpression of miR‐285 and silence of Br‐C inhibited the expression of Br‐C and other ecdysone signaling pathway genes, including E74, E75, ECR, FTZ‐F1, and HR3. On the contrary, suppressing miR‐285 obtained opposite results. Further experiments showed that 20‐hydroxyecdysone down‐regulated miR‐285 and up‐regulated Br‐C and above‐mentioned genes, whereas juvenile hormone alalogue (JHA) resulted in opposite effects. CONCLUSION: Our results reveal that miR‐285 is involved in mediating the metamorphosis in G. daurica by targeting Br‐C in the ecdysone signaling pathway. miR‐285 and its target Br‐C could be as a potential target for G. daurica management. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The forkhead box O (FoxO), as a conserved transcription factor, plays an indispensable role in regulating insect diapause. However, how FoxO is regulated to control diapause in insects remains unknown. In this study, we discovered functional binding sites for miR‐2765‐3p in the 3′ untranslated region of FoxO in Galeruca daurica. The luciferase reporter assay showed that miR‐2765‐3p targeted FoxO and suppressed its expression. The expression profiles of miR‐2765‐3p and FoxO displayed opposite patterns during the female developmental process. Overexpression of miR‐2765‐3p by the injection of the miR‐2765‐3p agomir into adult females reduced FoxO expression, leading to the suppression of lipid accumulation, promotion of ovarian development, and inhibition of reproductive diapause. This is similar to the phenotype that results from the depletion of FoxO by injecting dsFoxO into adult females. In addition, the repression of miR‐2765‐3p by injecting the miR‐2765‐3p antagomir increased the FoxO transcript level, leading to the stimulation of lipid accumulation, depression of ovarian development, and induction of reproductive diapause. A hormone injection assay showed that the juvenile hormone (JH) agonist (methoprene) upregulated miR‐2765‐3p and downregulated FoxO. Notably, injecting methoprene rescued ovarian development defects associated with miR‐2765‐3p inhibition. These findings indicate that the JH/miR‐2765‐3p/FoxO axis plays a vital role in the regulation of reproductive diapause in G. daurica. [ABSTRACT FROM AUTHOR]

The plant bug Lygus pratensis Linnaeus (Hemiptera: Miridae) is an important insect pest of alfalfa in grassland farming in northern China. A field population of L. pratensis was selected in the laboratory for 14 consecutive generations with lambda-cyhalothrin to generate 42.555-fold resistance. Selection also induced low cross-resistance to imidacloprid and beta-cypermethrin, and medium cross-resistance to deltamethrin. Realized heritability (h 2 ) of lambda-cyhalothrin resistance was 0.339. Susceptible baselines of L. pratensis were established for five insecticides using the glass-vial method, the values of which were 6.849, 3.423, 8.778, 3.559, and 117.553 ng/cm2 for phoxim, methomyl, imidacloprid, lambda-cyhalothrin, and avermectin, respectively, along with the calculated LC99 diagnostic doses. This resistance risk assessment study suggests that a high risk of lambda-cyhalothrin resistance exists in the field. In addition, a 5-year field investigation of resistance monitoring of L. pratensis was conducted in seven alfalfa regions in farming-pastoral ecotones in northern China. The resistance levels of most populations were very low for phoxim, methomyl, and avermectin, with an upward trend for lambda-cyhalothrin resistance in the DK (Dengkou County), TKT (Tuoketuo County), XL (Xilinhot), and LX (Linxi County) populations during 2015–2019, and medium resistance level to imidacloprid in the TKT population in five years we sampled. The study provided information on chemical control, lambda-cyhalothrin resistance development, baseline susceptibility, and the status of resistance to five commonly-used insecticides against L. pratensis. These results could be used to optimize pyrethroid insecticide use as part of a pest integrated resistance management strategy against this key insect pest of alfalfa. [ABSTRACT FROM AUTHOR]

[Objectives] To clone the full cDNA sequence of the Galeruca daurica (Coleoptera: Chrysomellidae) juvenile hormone binding protein gene, analyze its molecular characteristics and expression profiles, and provide information that will help further clarify its function in the development and summer diapause of G. daurica. [Methods] Based on the transcriptome database of G. daurica, RACE technology was used to clone the full cDNA sequence of GdJHBP, the molecular characteristics of which were analyzed by software, including ORF Finder, SignaIP, DNAMAN and TMHMM. A neighbor joining (NJ) phylogenetic tree was constructed using MEGA 6.0 software. Real-time quantitative PCR (RT-qPCR) was used to assay the expression profiles of GdJHBP in different developmental stages and adult tissues, and under high temperature. [Results] The full cDNA sequence of GdJHBP (GenBank accession No.: MG460309) obtained from G. daurica was 826 bp in length with an open reading frame (ORF) 714 bp long, and encodes 237 amino acids with a predicted molecular weight of 26.58 ku and an isoelectric point of 4.37. The encoding protein is a single peptide without transmembrane structure, and contains a conserved JHBP family domain between 27 and 189 residues. Sequence alignment indicates a low amino acid sequence identity between the JHBPs of different insects; the highest identity, with Rhynchophorus ferrugineus RfJHBP and Leptinotarsa decemlineata LdJHBP 3p2, was only 30%. Phylogenetic analysis indicates that GdJHBP is most closely related to a hemolymph JHBP from R. ferrugineus. RT-qPCR indicates that GdJHBP was expressed in various developmental stages of G. daurica with the highest expression in larvae and the lowest in eggs and pupae. Expression of GdJHBP was relatively low during the summer diapause of G. daurica adults and was higher both before, and after, diapause. GdJHBP was more highly expressed in the thorax and abdomen than in the head during adult development. High temperatures (30 to 40...) induced GdJHBP to be up-regulated with peak expression at 35 ... [Conclusion] GdJHBP belongs to the hemolymph JHBP family and may play an important role in the development and summer diapause of G. daurica. [ABSTRACT FROM AUTHOR]

Using the thermocouple method, the supercooling point (SCP) and cold hardiness of Pararcyplera microptera meridionalis eggs were measured in the laboratory. The soil water content significantly affected the water content of pre-diapause eggs, but had no significant effect on the SCP, and the water content of pre-diapause eggs rose with the increasing soil water content. There were highly significant differences among the SCPs, water contents or fat contents in the eggs at different developmental stages. With the egg-s development, the water content decreased from 51. 5% at oviposition to 46. 8% in 120 days after oviposition, the fat content increased from 10. 5% (fresh mass) /19. 0% (dry mass) to 14. 5% (fresh mass) /28. 9% (dry mass), and the SCP declined from -23. 5 °Cto -30. 0 °C. There was a significant correlation between the SCP and the water content or fat content. The SCPs of deep-diapause eggs were lower than those of pre-and earlydiapause eggs. The different low temperatures and treatment durations significantly affected the survival rate of diapause eggs. The lethal low temperature (Ltemp50 ) for 12 h exposure was -27. 3 and the lethal time (Ltime50) at -25 °C was 22. 73 days. As the mean SCPs of diapause eggs was much similar to their Ltemp50, the SCP could be considered as a good indicator of cold hardiness for P. m. meridionalis eggs and this species is a freeze-intolerant insect. [ABSTRACT FROM AUTHOR]

A comparative study was conducted on the life table parameters of Aphis gossypii reared on five host plant species at (25±1) ° in laboratory. There existed significant differences in the durations of various developmental stages, adult longevity, mean offspring number per day, net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time, and population doubling time for the A. gossypii populations reared on the host plants. For the aphids on Lagenaria siceraria var. turbinate, they needed the longest time (5. 84 days) to complete one generation, but for those on the other four plants, no significant differences were observed, with the time needed ranged from 5. 24 to 5. 45 days. The adult longevity was the longest (20. 04 days) on Cucumis sativus, but had no significant differences on the other four host plants, being from 14. 76 to 16. 03 days. The populations' survival curves on all test host plants were of Deevey I, i. e. , the death mainly occurred during late period. The survival rate on C. sativus was higher than those on the other four host plants. Based on the intrinsic rates of increase of A. gossypii, its host suitability was in the order of Cucumis melo var. saccharinus > Lagenaria siceraria var. turbinate > Cucurbita moschata var. melonaeformis > Cucumis sativus > Cucurbita pepo var. medullosa. [ABSTRACT FROM AUTHOR]

Using the thermocouple method, the supercooling point (SCP) and cold hardiness of Pararcyplera microptera meridionalis eggs were measured in the laboratory. The soil water content significantly affected the water content of pre-diapause eggs, but had no significant effect on the SCP, and the water content of pre-diapause eggs rose with the increasing soil water content. There were highly significant differences among the SCPs, water contents or fat contents in the eggs at different developmental stages. With the egg' s development, the water content decreased from 51.5% at oviposition to 46.8% in 120 days after oviposition, the fat content increased from 10.5% (fresh mass)/19.0% (dry mass) to 14.5% (fresh mass)/28.9% (dry mass), and the SCP declined from -23.5 degrees C to -30.0 degrees C. There was a significant correlation between the SCP and the water content or fat content. The SCPs of deep-diapause eggs were lower than those of pre- and early-diapause eggs. The different low temperatures and treatment durations significantly affected the survival rate of diapause eggs. The lethal low temperature (Ltemp50) for 12 h exposure was -27.3 degrees C and the lethal time (Ltime50) at -25 degrees C was 22.73 days. As the mean SCPs of diapause eggs was much similar to their Ltemp50, the SCP could be considered as a good indicator of cold hardiness for P. m. meridionalis eggs and this species is a freeze-intolerant insect.

A comparative study was conducted on the life table parameters of Aphis gossypii reared on five host plant species at (25 +/- 1) degrees C in laboratory. There existed significant differences in the durations of various developmental stages, adult longevity, mean offspring number per day, net reproductive rate, intrinsic rate of increase, finite rate of increase, mean generation time, and population doubling time for the A. gossypii populations reared on the host plants. For the aphids on Lagenaria siceraria var. turbinate, they needed the longest time (5.84 days) to complete one generation, but for those on the other four plants, no significant differences were observed, with the time needed ranged from 5.24 to 5.45 days. The adult longevity was the longest (20.04 days) on Cucumis sativus, but had no significant differences on the other four host plants, being from 14.76 to 16.03 days. The populations' survival curves on all test host plants were of Deevey I, i. e., the death mainly occurred during late period. The survival rate on C. sativus was higher than those on the other four host plants. Based on the intrinsic rates of increase of A. gossypii, its host suitability was in the order of Cucumis melo var. saccharinus > Lagenaria siceraria var. turbinate > Cucurbita moschata var. melonaeformis > Cucumis sativus > Cucurbita pepo var. medullosa.

The laboratory study with no free choice means showed that the host preference of Liriomyza huidobrensis (Blanchard) adult differed significantly with test plants. Phaseolus vulgaris, Chrysanthemum coronarium and Cucurbita pepo were the most preferred, while Lycopersicum esculenturn and Brassica oleracea were the least. Correlative analysis indicated that the host preference of L. huidobrensis adult had a significant positive correlation with the content of soluble sugar, but less correlation with soluble protein and chlorophyll contents in host foliage.