Penicillium-Infected Apples Benefit Larval Development of Conogethes punctiferalis via Alterations of Their Gut Bacteria Community and Gene Expression

Mother knows worst? Fungal infection enhances corn flavonoid of wogonin to inhibit Conogethes punctiferalis larval growth

Pathogen infection in host plants can alter the attraction and adaptability of herbivorous insects. Female adult insects often exhibit selective behaviours based on their environmental experiences, enabling their offspring to avoid adverse conditions and ensuring healthy growth and development. However, comprehensive studies integrating both the perspectives of offspring fitness and host plant to validate the selective significance of such parental 'Mother knows worst' experiences remain limited. Building on our previous findings that female Conogethes punctiferalis (Yellow peach moth, YPM) adults exhibit oviposition avoidance behaviour towards corn infected with Trichoderma asperellum, we further confirmed that corn infected by T. asperellum significantly inhibits the growth and development of YPM larvae. Feeding on infected corn decreases larval gut microbiota diversity, core microbiota abundance and led to differential expression of key genes in juvenile hormone metabolic pathway. Moreover, the content of flavonoid wogonin, a secondary metabolite, was significantly increased in infected corn. In vitro feeding experiments revealed that wogonin negatively impacts YPM larval growth by causing the juvenile hormone accumulation and suppressing the abundance of core gut microbial strains. This study validates the adaptive significance of parental empiricism from the perspective of offspring, while further elucidating the mechanisms by which microbial-mediated plant resistance against insects, as well as for exploring and utilizing effective biocontrol resources against YPMs.

Nanomaterial-mediated RNAi reveals the effect of the oral secretory protein serine protease inhibitor on the growth of Conogethes punctiferalis larvae

The oral secretions of herbivorous insects play a pivotal role in insect-plant interactions and the regulation of insect physiology. Unlike the saliva of Hemiptera species, Lepidopteran oral secretions include both saliva and regurgitated gut fluids; yet research on their composition remains limited. This study focuses on yellow peach moth (YPM), Conogethes punctiferalis, a pest increasingly damaging maize. A total of 103 proteins were identified from oral secretions collected from larvae reared on corn and artificial diets, comprising 67 enzymes, 30 non-enzymes, and 6 unknowns. The identified enzyme proteins were primarily trypsin, lipase, and serine protease inhibitors (serpins). Further genomic investigation revealed 36 serpin genes in the YPM genome, distributed in clusters across various chromosomes, with some genes exhibiting partial synteny to homologous sequences in Ostrinia furnacalis. Among the identified serpin genes, the SpI gene (jg17839), which encoded the most abundant protein in YPM oral secretions, was found to exhibit peak expression in fifth-instar larvae and culticle tissues. Silencing of the SpI gene through nanomaterial-mediated RNA interference significantly reduced larval length, weight, pupation rates, and pupal weight, while also increased larval mortality. Moreover, interfering with SpI expression elevated juvenile hormone levels in the larvae. These findings indicate that the abundant SpI protein in YPM oral secretions plays a vital role in larval growth and development by modulating internal hormone levels. This study enriches the database of lepidopteran oral secretion components, fostering a deeper understanding of their physiological roles and informing eco-friendly pest control strategies targeting these proteins in YPM.

The cultivable gut bacteria Enterococcus mundtii promotes early-instar larval growth of Conogethes punctiferalis via enhancing digestive enzyme activity

BACKGROUND

Gut bacteria are crucial in influencing insect development and even phenotypic plasticity. The yellow peach moth Conogethes punctiferalis, as a significant borer pest, has been the subject of limited reports regarding the structural and diversification changes in its gut microbiota during feeding, and their potential impacts on the growth and development of the host insects.

RESULTS

This study, employing 16S rRNA sequencing, demonstrates distinct shifts in the larvae gut microbiome of C. punctiferalis between different feeding stages, highlighting a pronounced diversity in the early-instar with Enterococcus as a predominant genus in laboratory populations. Through in vitro cultivation and sequencing, three bacterial strains - Micrococcus sp., Brevibacterium sp. and Enterococcus mundtii - were isolated and characterized. Bioassays revealed that E. mundtii-infused corn significantly boosts early-instar larval growth, enhancing both body length and weight. Quantitative PCR and spectrophotometry confirmed a higher abundance of E. mundtii in younger larvae, correlating with increased digestive enzyme activity and total protein levels.

CONCLUSION

This study reveals the heightened gut microbiota diversity in early instars of C. punctiferalis larvae, highlighting that Enterococcus represent a predominant bacteria in laboratory populations. In vitro cultivation and bioassays unequivocally demonstrate the significant role of the cultivable gut bacteria E. mundtii in promoting the growth of early-instar larva. These findings provide a solid theoretical foundation for advancing the comprehension of the intricate interactions between gut microbiota and insect hosts, as well as for the development of eco-friendly pest control technologies based on targeted manipulation of insect gut microbial communities. © 2024 Society of Chemical Industry.

Gut fungal diversity across different life stages of the onion fly Delia antiqua

A significant number of microorganisms inhabit the intestinal tract or the body surface of insects. While the majority of research on insect microbiome interaction has mainly focused on bacteria, of late multiple studies have been acknowledging the importance of fungi and have started reporting the fungal communities as well. In this study, high-throughput sequencing was used to compare the diversity of intestinal fungi in Delia antiqua (Diptera: Anthomyiidae) at different growth stages, and effect of differential fungi between adjacent life stages on the growth and development of D. antiqua was investigated. The results showed that there were significant differences in the α and β diversity of gut fungal communities between two adjacent growth stages. Among the dominant fungi, genera Penicillium and Meyerozyma and family Cordycipitaceae had higher abundances. Cordycipitaceae was mainly enriched in the pupal and adult (male and female) stages, Penicillium was mainly enriched in the pupal, 2nd instar and 3rd instar larval stages, and Meyerozyma was enriched in the pupal stage. Only three fungal species were found to differ between two adjacent growth stages. These three fungal species including Fusarium oxysporum, Meyerozyma guilliermondii and Penicillium roqueforti generally inhibited the growth and development of D. antiqua, with only P. roqueforti promoting the growth and development of female insects. This study will provide theoretical support for the search for new pathogenic microorganisms for other fly pests control and the development of new biological control strategies for fly pests.