摘要: Feeding behavior is critical for insect survival and fitness. Most researchers have explored the molecular basis of feeding behaviors by identifying and elucidating the function of olfactory receptors (ORs) and gustatory receptors (GRs). Other types of genes, such as transcription factors, have rarely been investigated, and little is known about their potential roles. The silkworm (Bombyx mori) is a well-studied monophagic insect which primarily feeds on mulberry leaves, but the genetic basis of its monophagy is still not understood. In this report, we focused on a transcription factor encoded by the Zfh3 gene, which is highly expressed in the silkworm central and peripheral nervous systems, including brain, antenna, and maxilla. To investigate its function, Zfh3 was abrogated using clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR associated protein 9 (Cas9) mutagenesis. Since Zfh3 knockout homozygotes are not viable, we studied feeding behavior in heterozygotes, and found that disruption of Zfh3 affects both gustation and olfaction. Mutant larvae lose preference for mulberry leaves, acquire the ability to consume an expanded range of diets, and exhibit improved adaptation to the M0 artificial diet, which contains no mulberry leaves. These results provide the first demonstration that a transcription factor modulates feeding behaviors in an insect.

摘要: The diversity of cell types in the brain and how these change during different developmental stages, remains largely unknown. The life cycle of insects is short and goes through 4 distinct stages including embryonic, larval, pupal, and adult stages. During postembryonic life, the larval brain transforms into a mature adult version after metamorphosis. The silkworm, Bombyx mori, is a lepidopteran model insect. Here, we characterized the brain cell repertoire of larval and adult B. mori by obtaining 50 708 single-cell transcriptomes. Seventeen and 12 cell clusters from larval and adult brains were assigned based on marker genes, respectively. Identified cell types include Kenyon cells, optic lobe cells, monoaminergic neurons, surface glia, and astrocyte glia. We further assessed the cell type compositions of larval and adult brains. We found that the transition from larva to adult resulted in great expansion of glial cells. The glial cell accounted for 49.8% of adult midbrain cells. Compared to flies and ants, the mushroom body kenyon cell is insufficient in B. mori, which accounts for 5.4% and 3.6% in larval and adult brains, respectively. Analysis of neuropeptide expression showed that the abundance and specificity of expression varied among individual neuropeptides. Intriguingly, we found that ion transport peptide was specifically expressed in glial cells of larval and adult brains. The cell atlas dataset provides an important resource to explore cell diversity, neural circuits and genetic profiles.

摘要: Locust (Locusta migratoria) has a single striated muscle myosin heavy chain (Mhc) gene, which contains 5 clusters of alternative exclusive exons and 1 differently included penultimate exon. The alternative exons of Mhc gene encode 4 distinct regions in the myosin motor domain, that is, the N-terminal SH3-like domain, one lip of the nucleotide-binding pocket, the relay, and the converter. Here, we investigated the role of the alternative regions on the motor function of locust muscle myosin. Using Sf9-baculovirus protein expression system, we expressed and purified 5 isoforms of the locust muscle myosin heavy meromyosin (HMM), including the major isoform in the thorax dorsal longitudinal flight muscle (FL1) and 4 isoforms expressed in the abdominal intersegmental muscle (AB1 to AB4). Among these 5 HMMs, FL1-HMM displayed the highest level of actin-activated adenosine triphosphatase (ATPase) activity (hereafter referred as ATPase activity). To identify the alternative region(s) responsible for the elevated ATPase activity of FL1-HMM, we produced a number of chimeras of FL1-HMM and AB4-HMM. Substitution with the relay of AB4-HMM (encoded by exon-14c) substantially decreased the ATPase activity of FL1-HMM, and conversely, the relay of FL1-HMM (encoded by exon-14a) enhanced the ATPase activity of AB4-HMM. Mutagenesis showed that the exon-14a-encoded residues Gly(474) and Asn(509) are responsible for the elevated ATPase activity of FL1-HMM. Those results indicate that the alternative relay encoded by exon-14a/c play a key role in regulating the ATPase activity of FL1-HMM and AB4-HMM.

摘要: MicroRNAs (miRNAs) are small non-coding RNAs that play pivotal roles in the host response to invading pathogens. Among these pathogens, Bombyx mori nucleopolyhedrovirus (BmNPV) is one of the main causes of substantial economic losses in sericulture, and there are relatively few studies on the specific functions of miRNAs in the B. mori-BmNPV interaction. Therefore, we conducted transcriptome sequencing to identify differentially expressed (DE) messenger RNAs (mRNAs) and miRNAs in the midgut of 2 B. mori strains (BmNPV-susceptible strain P50 and BmNPV-resistant strain A35) after BmNPV infection. Through correlation analysis of the miRNA and mRNA data, we identified a comprehensive set of 21 miRNAs and 37 predicted target mRNAs. Notably, miR-3351, which has high expression in A35, exhibited remarkable efficacy in suppressing BmNPV proliferation. Additionally, we confirmed that miR-3351 binds to the 3 ' untranslated region (3 ' UTR) of B. mori glutathione S-transferase epsilon 6 (BmGSTe6), resulting in its downregulation. Conversely, BmGSTe6 displayed an opposite expression pattern to miR-3351, effectively promoting BmNPV proliferation. Notably, BmGSTe6 levels were positively correlated with glutathione S-transferase activity, consequently influencing intracellular glutathione content in the infected samples. Furthermore, our investigation revealed the protective role of glutathione against BmNPV infection in BmN cells. In summary, miR-3351 modulates glutathione content by downregulating BmGSTe6 to inhibit BmNPV proliferation in B. mori. Our findings enriched the research on the role of B. mori miRNAs in the defense against BmNPV infection, and suggests that the antiviral molecule, glutathione, offers a novel perspective on preventing viral infection in sericulture.

摘要: The tanning hormone, Bursicon, is a neuropeptide secreted by the insect nervous system that functions as a heterodimer composed of Burs-alpha and Burs-beta subunits. It plays a critical role in the processes of cuticle tanning and wing expansion in insects. In this study, we successfully identified the AcBurs-alpha and AcBurs-beta genes in Aphis citricidus. The open reading frames of AcBurs-alpha and AcBurs-beta were 480 and 417 bp in length, respectively. Both AcBurs-alpha and AcBurs-beta exhibited 11 conserved cysteine residues. AcBurs-alpha and AcBurs-beta were expressed during all developmental stages of A. citricidus and showed high expression levels in the winged aphids. To investigate the potential role of AcBurs-alpha and AcBurs-beta in wing development, we employed RNA interference (RNAi) techniques. With the efficient silencing of AcBurs-alpha (44.90%) and AcBurs-beta (52.31%), malformed wings were induced in aphids. The proportions of malformed wings were 22.50%, 25.84%, and 38.34% in dsAcBurs-alpha-, dsAcBur-beta-, and dsAcBurs-alpha + dsAcBur-beta-treated groups, respectively. Moreover, feeding protein kinase A inhibitors (H-89) also increased the proportion of malformed wings to 30.00%. Feeding both double-stranded RNA and inhibitors (H-89) significantly downregulated the wing development-related genes nubbin, vestigial, notch and spalt major. Silence of vestigial through RNAi also led to malformed wings. Meanwhile, the exogenous application of 3 hormones that influence wing development did not affect the expression level of AcBursicon genes. These findings indicate that AcBursicon genes plays a crucial role in wing development in A. citricidus; therefore, it represents a potential molecular target for the control of this pest through RNAi-based approaches.