Viral-encoded microRNAs in host-pathogen interactions in silkworm

miR-278-3p targets ATG16L1 to modulate autophagy and suppresses CLas proliferation in Diaphorina citri

The phloem-limited bacterium Candidatus Liberibacter asiaticus (CLas) is the primary cause of citrus Huanglongbing (HLB) and is transmitted by the Asian citrus psyllid, Diaphorina citri. MicroRNAs (miRNAs) are key posttranscriptional regulators involved in various biological processes, yet their role in D. citri's response to CLas infection remains unclear. In this study, we found that autophagy levels were significantly elevated in CLas-infected D. citri compared to non-infected individuals. Modulating autophagy influenced CLas titers, suggesting its role in pathogen suppression. Small RNA sequencing identified differentially expressed miRNAs, with miR-278-3p being significantly downregulated by 72.3%. Functional analyses revealed that miR-278-3p regulates autophagy by targeting ATG16L1. Inhibition of miR-278-3p increased autophagosome formation, whereas its overexpression suppressed autophagy. Dual-luciferase reporter assays confirmed miR-278-3p directly binds to the 3'UTR of ATG16L1, negatively regulating its expression. Notably, miR-278-3p inhibition reduced CLas titers by 48.7%, demonstrating its role in pathogen defense. These findings provide novel insights into the molecular mechanisms underlying insect-pathogen interactions and highlight the potential of miRNA-based strategies for controlling plant diseases transmitted by insect vectors. Understanding these regulatory pathways may lead to innovative pest and disease management approaches in agriculture.

Common strategies in silkworm disease resistance breeding research

The silkworm, which is considered a model invertebrate organism, was the first insect used for silk production in human history and has been utilized extensively throughout its domestication. However, sericulture has been plagued by various pathogens that have  caused significant economic losses. To enhance the resistance of a host to its pathogens,numerous strategies have been developed. For instance, gene-editing techniques have been applied to a wide range of organisms, effectively solving a variety of experimental problems. This review focuses on several common silkworm pests and their pathogenic mechanisms, with a particular emphasis on breeding for disease resistance to control multiple types of silkworm diseases. The review also compares the advantages and disadvantages of transgenic technology and gene-editing systems. Finally, the paper provides a brief summary of current strategies used in breeding silkworm disease resistance, along with a discussion of the establishment of existing technologies and their future application prospects. © 2023 Society of Chemical Industry.

A cypovirus encoded microRNA negatively regulates the NF-κB pathway to enhance viral multiplication in Silkworm, Bombyx mori

MicroRNAs (miRNAs) are small non-coding RNAs that function as novel gene expression regulators at the post-transcriptional level. Not with standing that the biogenesis and function of miRNAs are well-understood in eukaryotes, little is known about RNA virus-encoded miRNAs. Bombyx mori cypovirus (BmCPV) is a double-stranded RNA virus with a segmented genome that causes cytoplasmic polyhedrosis disease in silkworm larvae. To date, the interaction between BmCPV and silkworm remains largely unclear. 22 candidate BmCPV-encoded miRNAs were identified in this study through small RNA sequencing, stem-loop RT-PCR and qRT-PCR. Then, generation and function analyses were conducted on one of the candidate miRNAs, BmCPV-miR-1, in the BmN cells and the silkworm larvae by RNA interference, quantitative PCR, dual-luciferase assay. Our results revealed that BmCPV-miR-1 was encoded by BmCPV genome RNA rather than the degraded fragments of the viral genome. Its generation depended on Dicer-1 and might also be correlated with Dicer-2, Argonaute-1 and Argonaute-2. Moreover, BmCPV-miR-1 could suppress the expression of the target gene, B. mori inhibitor of nuclear factor kappa-B kinase subunit beta (BmIKKβ), via binding to the target mRNA 3'-untranslated region, which fine-tuned the host NF-κB signaling pathway and consequently enhanced viral replication. Our results provide new evidence supporting the hypothesis that RNA viruses could generate miRNAs to modulate antiviral host defense.