Regulation of Hormone-Related Genes in Ericerus pela (Hemiptera: Coccidae) for Dimorphic Metamorphosis

Functional studies of McSTE24, McCYP305a1, and McJHEH, three essential genes act in cantharidin biosynthesis in the blister beetle (Coleoptera: Meloidae)

Cantharidin is a toxic defensive substance secreted by most blister beetles when attacked. It has been used to treat many complex diseases since ancient times and has recently regained popularity as an anticancer agent. However, the detailed mechanism of the cantharidin biosynthesis has not been completely addressed. In this study, we cloned McSTE24 (encoding STE24 endopeptidase) from terpenoid backbone pathway, McCYP305a1 (encoding cytochrome P450, family 305) and McJHEH [encoding subfamily A, polypeptide 1 and juvenile hormone (JH) epoxide hydrolase] associated to JH synthesis/degradation in the blister beetle Mylabris cichorii (Linnaeus, 1758, Coleoptera: Meloidae). Expression pattern analyses across developmental stages in adult males revealed that the expressions of 3 transcripts were closely linked to cantharidin titer exclusively during the peak period of cantharidin synthesis (20-25 days old). In contrast, at other stages, these genes may primarily regulate different biological processes. When RNA interference with double-stranded RNA suppressed the expressions of the 3 genes individually, significant reductions in cantharidin production were observed in males and also in females following McJHEH knockdown, indicating that these 3 genes might primarily contribute to cantharidin biosynthesis in males, but not in females, while females could self-synthesis a small amount of cantharidin. These findings support the previously hypothesized sexual dimorphism in cantharidin biosynthesis during the adult phase. McCYP305a1 collaborates with its upstream gene McSTE24 in cantharidin biosynthesis, while McJHEH independently regulates cantharidin biosynthesis in males.

Mosquito E-20-Monooxygenase Gene Knockout Increases Dengue Virus Replication in Aedes aegypti Cells

E-20-monooxygenase (E20MO) is an enzymatic product of the shade (shd) locus (cytochrome p450, E20MO). Initially discovered in Drosophila, E20MO facilitates the conversion of ecdysone (E) into 20-hydroxyecdysone (20E) and is crucial for oogenesis. Prior research has implicated 20E in growth, development, and insecticide resistance. However, little attention has been given to the association between the E20MO gene and DENV2 infection. The transcriptome of Ae. aegypti cells (Aag2 cells) infected with DENV2 revealed the presence of the E20MO gene. The subsequent quantification of E20MO gene expression levels in Aag2 cells post-DENV infection was carried out. A CRISPR/Cas9 system was utilized to create an E20MO gene knockout cell line (KO), which was then subjected to DENV infection. Analyses of DENV2 copies in KO and wild-type (WT) cells were conducted at different days post-infection (dpi). Plasmids containing E20MO were constructed and transfected into KO cells, with pre- and post-transfection viral copy comparisons. Gene expression levels of E20MO increased after DENV infection. Subsequently, a successful generation of an E20MO gene knockout cell line and the verification of code-shifting mutations at both DNA and RNA levels were achieved. Furthermore, significantly elevated DENV2 RNA copies were observed in the mid-infection phase for the KO cell line. Viral RNA copies were lower in cells transfected with plasmids containing E20MO, compared to KO cells. Through knockout and plasmid complementation experiments in Aag2 cells, the role of E20MO in controlling DENV2 replication was demonstrated. These findings contribute to our understanding of the intricate biological interactions between mosquitoes and arboviruses.

The transcriptome of Icerya aegyptiaca (Hemiptera: Monophlebidae) and comparison with neococcoids reveal genetic clues of evolution in the scale insects

BACKGROUND

Scale insects are worldwide sap-sucking parasites, which can be distinguished into neococcoids and non-neococcoids. Neococcoids are monophyletic with a peculiar reproductive system, paternal genome elimination (PGE). Different with neococcoids, Iceryini, a tribe in non-neococcoids including several damaging pests, has abdominal spiracles, compound eyes in males, relatively abundant wax, unique hermaphrodite system, and specific symbionts. However, the current studies on the gene resources and genomic mechanism of scale insects are mainly limited in the neococcoids, and lacked of comparison in an evolution frame.

RESULT

We sequenced and de novo assembled a transcriptome of Icerya aegyptiaca (Douglas), a worldwide pest of Iceryini, and used it as representative of non-neococcoids to compare with the genomes or transcriptomes of other six species from different families of neococcoids. We found that the genes under positive selection or negative selection intensification (simplified as "selected genes" below) in I. aegyptiaca included those related to neurogenesis and development, especially eye development. Some genes related to fatty acid biosynthesis were unique in its transcriptome with relatively high expression and not detected in neococcoids. These results may indicate a potential link to the unique structures and abundant wax of I. aegyptiaca compared with neococcoids. Meanwhile, genes related to DNA repair, mitosis, spindle, cytokinesis and oogenesis, were included in the selected genes in I. aegyptiaca, which is possibly associated with cell division and germ cell formation of the hermaphrodite system. Chromatin-related process were enriched from selected genes in neococcoids, along with some mitosis-related genes also detected, which may be related to their unique PGE system. Moreover, in neococcoid species, male-biased genes tend to undergo negative selection relaxation under the PGE system. We also found that the candidate horizontally transferred genes (HTGs) in the scale insects mainly derived from bacteria and fungi. bioD and bioB, the two biotin-synthesizing HTGs were exclusively found in the scale insects and neococcoids, respectively, which possibly show potential demand changes in the symbiotic relationships.

CONCLUSION

Our study reports the first I. aegyptiaca transcriptome and provides preliminary insights for the genetic change of structures, reproductive systems and symbiont relationships at an evolutionary aspect. This will provide a basis for further research and control of scale insects.

Identification of the Key Pathways and Genes Involved in the Wax Biosynthesis of the Chinese White Wax Scale Insect (Ericerus pela Chavannes) by Integrated Weighted Gene Coexpression Network Analysis

The white wax secreted by the male insects of the Chinese white wax scale (CWWS) is a natural high-molecular-weight compound with important economic value. However, its regulatory mechanism of wax biosynthesis is still unclear. In this study, a weighted gene coexpression network analysis (WGCNA) was used to analyze transcriptome data of first- and second-instar females, early and late female adults, and first- and second-instar males. A total of 19 partitioned modules with different topological overlaps were obtained, and three modules were identified as highly significant for wax secretion (p < 0.05). A total of 30 hub genes were obtained through screening, among which elongation of very-long-chain fatty acids protein (ELOVL) and fatty acyl-CoA reductase (FAR) are important catalytic enzymes of fatty acid metabolism. Furthermore, their metabolic catalytic products are involved in the synthesis of wax biosynthesis. The results demonstrate that WGCNA can be used for insect transcriptome analysis and effectively screen out the key genes related to wax biosynthesis.

Insecticidal Triterpenes in Meliaceae: Plant Species, Molecules and Activities: Part Ⅰ (Aphanamixis-Chukrasia)

Plant-originated triterpenes are important insecticidal molecules. The research on insecticidal activity of molecules from Meliaceae plants has always received attention due to the molecules from this family showing a variety of insecticidal activities with diverse mechanisms of action. In this paper, we discuss 102 triterpenoid molecules with insecticidal activity of plants of eight genera (Aglaia, Aphanamixis, Azadirachta, Cabralea, Carapa, Cedrela, Chisocheton, and Chukrasia) in Meliaceae. In total, 19 insecticidal plant species are presented. Among these species, Azadirachta indica A. Juss is the most well-known insecticidal plant and azadirachtin is the active molecule most widely recognized and highly effective botanical insecticide. However, it is noteworthy that six species from Cedrela were reported to show insecticidal activity and deserve future study. In this paper, a total of 102 insecticidal molecules are summarized, including 96 nortriterpenes, 4 tetracyclic triterpenes, and 2 pentacyclic triterpenes. Results showed antifeedant activity, growth inhibition activity, poisonous activity, or other activities. Among them, 43 molecules from 15 plant species showed antifeedant activity against 16 insect species, 49 molecules from 14 plant species exhibited poisonous activity on 10 insect species, and 19 molecules from 11 plant species possessed growth regulatory activity on 12 insect species. Among these molecules, azadirachtins were found to be the most successful botanical insecticides. Still, other molecules possessed more than one type of obvious activity, including 7-deacetylgedunin, salannin, gedunin, azadirone, salannol, azadiradione, and methyl angolensate. Most of these molecules are only in the primary stage of study activity; their mechanism of action and structure–activity relationship warrant further study.

Potential Pathways and Genes Involved in Lac Synthesis and Secretion in Kerria chinensis (Hemiptera: Kerriidae) Based on Transcriptomic Analyses

Lac is a type of natural resin secreted by lac insects and is widely used in the military and other industries because of its excellent adhesion and insulation properties. The main ingredients of lac are lactones and lactides, which are formed from hydroxy fatty acids and sesquiterpene esters. In this study, we measured lac secretion rates by the insect Kerria chinensis at different developmental stages and identified lac secretion-minimum and lac secretion-active stages of the insect. We then analyzed transcriptomes of lac secretion-minimum and lac secretion-active stages of the insect. Based on expression profiles of genes in different stages of the insect, we identified pathways and genes that are potentially involved in lac synthesis and secretion in K. chinensis. Our study lays a foundation for future studies to reveal the molecular mechanisms and pathways of lac synthesis and secretion in this beneficial insect.