Molecular characterization and functional analysis of cytochrome P450-mediated detoxification CYP302A1 gene involved in host plant adaptation in Spodoptera frugieprda

Effects of miR-306 Perturbation on Life Parameters in the English Grain Aphid, Sitobion avenae (Homoptera: Aphididae)

MicroRNAs (miRNA) play a vital role in insects' growth and development and have significant potential value in pest control. Previously, we identified miR-306 from small RNA libraries within the English grain aphid, Sitobion avenae, a devasting insect pest for wheat. miR-306 not only involves in wing morphogenesis, but also is critically important for aphid survival. Its specific impacts on the life history traits, however, remain unclear. Here, we evaluate the impact of miR-306 perturbation on S. avenae populations using a two-sex life table approach. This comprehensive analysis revealed that miR-306 perturbation significantly prolongs the developmental stages (9.64% and 8.20%) and adult longevity of S. avenae, while decreasing pre-adult survival rate (41.45% and 38.74%) and slightly reducing average fecundity (5.80% and 13.05%). Overall, miR-306 perturbation negatively affects the life table parameters of the aphid population. The population prediction models show a significant decline in the aphid population 60 days post interference, compared to the control groups (98.14% and 97.76%). Our findings highlight the detrimental effects of miR-306 perturbation on S. avenae population growth and suggest potential candidate genes for the development of RNAi-based biopesticides targeted specifically at this pest species.

Plasticity of the Gene Transcriptional Level and Microbiota in the Gut Contributes to the Adaptability of the Fall Armyworm to Rice Plants

Insects coordinate a variety of mechanisms to overcome the feeding challenges, including gene transcriptional plasticity and stable symbioses in the gut. Here, Spodoptera frugiperda larvae were reared on corn and rice plants for successive generations to obtain two specific strains. The rice strain displayed a longer developmental period, lower female fecundity, and intrinsic growth rate at G1 and G5 but not at G10. KEGG analysis of the G1, G5, and G11 gut transcriptome indicated that detoxification enzymes might play vital roles in host adaptation. RNAi-mediated knockdown of CYP12A2 and UGT41B8, which were highly expressed in the gut of the rice strain, significantly reduced the larval adaptability to rice. Besides, the dsCYP12A2-treated larvae displayed an increased sensitivity to luteolin, a flavonoid phytochemical. The KEGG function prediction of gut microbiota indicated that the high enrichment level of metabolism in the rice strain would play essential roles in rice adaptation.

The effects of carvacrol on development and gene expression profiles in Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a highly polyphagous agricultural pest that is widely distributed around the world and causes severe crop yield loss. Carvacrol showed adverse effects on many pests, such as larval death and growth inhibition. While the effects of carvacrol on S. frugiperda larvae are not yet known. In this study, the effects of carvacrol on S. frugiperda, including larval growth inhibition and mortality induction, were observed. The detoxification and digestive enzyme activities of larvae with 1.0 and 2.0 g/kg carvacrol treatments were analyzed. Carvacrol boosted the enzyme activities of carboxylesterase (CarE) and glutathione S-transferase (GST) while decreasing the activities of α-amylase (AMS), lipase (LIP), and trypsin. A total of 3422 differentially expressed genes were identified in the larvae treated with 2.0 g/kg carvacrol, of which the DEGs involved in xenobiotic detoxification, food digestion, and insecticidal targets were further examined. These results suggest that carvacrol could regulate growth and development by affecting the process of food digestion, and exert its toxicity on the larvae through interaction with a variety of insecticidal targets. While the altered expressions of detoxification enzymes might be related to the detoxification and metabolism of carvacrol. Our findings offer a theoretical foundation for the use of carvacrol for S. frugiperda control in the field.

Function Analysis of Cholesterol 7-Desaturase in Ovarian Maturation and Molting in Macrobrachium nipponense: Providing Evidence for Reproductive Molting Progress

The Cholesterol 7-desaturase gene plays an important role in insect ecdysone synthesis, but its role in ovarian development has not been reported. In this study, characteristics and the phylogenetic relationship of Cholesterol 7-desaturase were identified by bioinformatics. qPCR showed that the Mn-CH7D gene was highly expressed in the ovary, which was much higher than that in other tissues, and the expression level of Mn-CH7D reached the highest level at the third stage of the ovarian development stage (O-III). During embryonic development, the Mn-CH7D gene expression was highest in the zoea stage. The function of the Mn-CH7D gene was explored by RNA interference. The experimental group was injected with Mn-CH7D dsRNA through the pericardial cavity of M. nipponense, while the control group was injected with the same volume of dsGFP. Statistical analysis of gonadal development and GSI calculation showed that the silencing of Mn-CH7D resulted in the suppression of gonadal development. In addition, the molting frequency of the experimental group was significantly lower than that of the control group during the second molting cycle after silencing Mn-CH7D. On the seventh day after silencing, ecdysone content in the experimental group was significantly reduced. These results demonstrated that the Mn-CH7D gene played a dual role in ovarian maturation and molting of M. nipponense.