ALKBH8 as a potential N6 -methyladenosine (m6 A) eraser in insects

Exploring the Role of mRNA Methylation in Insect Biology and Resistance

RNA methylation, characterized by modifications such as N6-methyladenosine, 5-methylcytosine, and N1-methyladenosine plays a crucial role in post-transcriptional gene regulation across diverse biological systems. While research on RNA methylation has predominantly focused on mammals, particularly its roles in epigenetic regulation and cancer biology, recent studies in insects have begun to explore their extensive functions in insect physiology. This review examines the mechanisms by which RNA methylation regulates growth, development, reproduction, environmental adaptation, and immune response in insects, providing insights into the biological characteristics of these organisms without prematurely speculating on pest control strategies. It aims to offer valuable insights into the role of RNA methylation in insect biology and resistance.

Transcriptome-wide N6-methyladenosinem modifications analysis of growth and fumonisins production in Fusarium proliferatum causing banana crown rot

Crown rot caused by Fusarium proliferatum is a severe postharvest disease of banana fruit. The N6-methyladenosine (m6A) modification is the most common type of RNA modification and regulates gene expression in eukaryotes. Here, we analyzed transcriptome-wide changes in m6A methylation to investigate post-transcriptional regulation mechanisms of growth and fumonisin biosynthesis of F. proliferatum after fluopyram (Flu) treatment. The results demonstrated that Flu treatment inhibited F. proliferatum growth but induced fumonisins (FB1 and FB2) production both in vitro and in vivo. A transcriptome-wide m6A methylation profile showed that m6A hypomethylation was induced by Flu and enriched in start codons and the 3' untranslated region. FpAlkbh8 and FpYthdc1 may contribute to the decrease in m6A modifications after Flu treatment. The expression levels of m6A-containing mRNAs were higher than those of non-m6A-containing mRNAs. Furthermore, Flu decreased the acetyl-CoA content and regulated glycolysis and tricarboxylic acid cycle through m6A modifications, diverting the acetyl-CoA flux into fumonisin biosynthesis. Importantly, Flu-mediated regulation of energy and reactive oxygen species metabolism, cell wall and membrane, and transcription factors was associated with m6A modifications. Collectively, this study provides potential novel targets for improving fungicide efficiency to control fungal disease and highlights the potential of environmental risks of fungicides.

Genome-wide characterization of the AlkB homolog (ALKBH) gene family in Litopenaeus vannamei identifies LvALKBH1 and LvALKBH8 as promising crustacean m6A demethylases involved in molting regulation and ammonia stress response

N6-methyladenosine (m6A) is the most abundant chemical modification on eukaryotic mRNAs. In crustaceans, the absence of canonical m6A demethylases, namely fat mass and obesity-associated protein (FTO) and AlkB Homolog 5 (ALKBH5), poses an unresolved puzzle about the m6A demethylation machinery of these invertebrates. Here, a genome-wide search for potential ALKBH gene family members in the whiteleg shrimp Litopenaeus vannamei was conducted. Six homologues of the ALKBH family were identified from the genome of L. vannamei, and comparative genomics analysis indicated that ALKBH3 and ALKBH5 are likely to exist in the common ancestor of arthropods and molluscs but are then lost in arthropods. Except for LvALKBH4 and LvALKBH7, all LvALKBH proteins possessed a typical 2OG-Fe(II)_Oxy_2 functional domain. Functional experiments revealed that LvALKBH1 and LvALKBH8 possessed significant m6A demethylation activity. Moreover, LvALKBH1 and LvALKBH8 significantly affected the m6A methylation and expression levels of the ecdysone receptor (EcR), retinoid X receptor (RXR), aspartate aminotransferase (AST), and glutamine synthetase (GS), implying their potential roles in regulating shrimp molting and ammonia toxicity resistance. The study provides important baseline information on the molecular characteristics of the ALKBH gene family in shrimp, and fills a current research gap concerning the m6A demethylation toolkit of crustaceans.

Wolbachia elevates host methyltransferase expression and alters the m6A methylation landscape in Aedes aegypti mosquito cells

Wolbachia pipientis is an intracellular endosymbiotic bacterium that blocks the replication of several arboviruses in transinfected Aedes aegypti mosquitoes, yet its antiviral mechanism remains unknown. For the first time, we employed Nanopore direct RNA sequencing technology to investigate the impact of wAlbB strain of Wolbachia on the host's N6-methyladenosine (m6A) machinery and post-transcriptional modification landscape. Our study revealed that Wolbachia infection elevates the expression of genes involved in the mosquito's m6A methyltransferase complex. However, knocking down these m6A-related genes did not affect Wolbachia density. Nanopore sequencing identified 1,392 differentially modified m6A DRACH motifs on mosquito transcripts, with 776 showing increased and 616 showing decreased m6A levels due to Wolbachia. These m6A sites were predominantly enriched in coding sequences and 3'-untranslated regions. Gene Ontology analysis revealed that genes with reduced m6A levels were over-represented in functional GO terms associated with purine nucleotide binding functions critical in the post-transcriptional modification process of m6A. Differential gene expression analysis of the Nanopore data uncovered that a total of 643 protein-coding genes were significantly differentially expressed, 427 were downregulated, and 216 were upregulated. Several classical and non-classical immune-related genes were amongst the downregulated DEGs. Notably, it revealed a critical host factor, transmembrane protein 41B (TMEM41B), which is required for flavivirus infection, was upregulated and methylated in the presence of Wolbachia. Indeed, there is a strong correlation between gene expression being upregulated in genes with both increased and decreased levels of m6A modification, respectively. Our findings underscore Wolbachia's ability to modulate many intracellular aspects of its mosquito host by influencing post-transcriptional m6A modifications and gene expression, and it unveils a potential link behind its antiviral properties.

RNA modifications in insects

More than 100 RNA chemical modifications to cellular RNA have been identified. N 6-methyladenosine (m6A) is the most prevalent modification of mRNA. RNA modifications have recently attracted significant attention due to their critical role in regulating mRNA processing and metabolism. tRNA and rRNA rank among the most heavily modified RNAs, and their modifications are essential for maintaining their structure and function. With our advanced understanding of RNA modifications, increasing evidence suggests RNA modifications are important in regulating various aspects of insect life. In this review, we will summarize recent studies investigating the impact of RNA modifications in insects, particularly highlighting the role of m6A in insect development, reproduction, and adaptation to the environment.

Recent advances of m6A methylation in skeletal system disease

Skeletal system disease (SSD) is defined as a class of chronic disorders of skeletal system with poor prognosis and causes heavy economic burden. m6A, methylation at the N6 position of adenosine in RNA, is a reversible and dynamic modification in posttranscriptional mRNA. Evidences suggest that m6A modifications play a crucial role in regulating biological processes of all kinds of diseases, such as malignancy. Recently studies have revealed that as the most abundant epigentic modification, m6A is involved in the progression of SSD. However, the function of m6A modification in SSD is not fully illustrated. Therefore, make clear the relationship between m6A modification and SSD pathogenesis might provide novel sights for prevention and targeted treatment of SSD. This article will summarize the recent advances of m6A regulation in the biological processes of SSD, including osteoporosis, osteosarcoma, rheumatoid arthritis and osteoarthritis, and discuss the potential clinical value, research challenge and future prospect of m6A modification in SSD.

RNA m6 A Methylation Suppresses Insect Juvenile Hormone Degradation to Minimize Fitness Costs in Response to A Pathogenic Attack

Bioinsecticides and transgenic crops based on the bacterial pathogen Bacillus thuringiensis (Bt) can effectively control diverse agricultural insect pests, nevertheless, the evolution of resistance without obvious fitness costs has seriously eroded the sustainable use of these Bt products. Recently, it has been discovered that an increased titer of juvenile hormone (JH) favors an insect host (Plutella xylostella) to enhance fitness whilst resisting the Bt pathogen, however, the underlying regulatory mechanisms of the increased JH titer are obscure. Here, the involvement of N6 -methyladenosine (m6 A) RNA modification in modulating the availability of JH in this process is defined. Specifically, it is found that two m6 A methyltransferase subunit genes, PxMettl3 and PxMettl14, repress the expression of a key JH-degrading enzyme JH esterase (JHE) to induce an increased JH titer, mitigating the fitness costs associated with a robust defense against the Bt pathogen. This study identifies an as-yet uncharacterized m6 A-mediated epigenetic regulator of insect hormones for maintaining fitness during pathogen defense and unveils an emerging Bt resistance-related m6 A methylation atlas in insects, which further expands the functional landscape of m6 A modification and showcases the pivotal role of epigenetic regulation in host-pathogen interactions.

N6-adenosine (m6A) mRNA methylation is required for Tribolium castaneum development and reproduction

Gene expression is regulated at various levels, including post-transcriptional mRNA modifications, where m6A methylation is the most common modification of mRNA. The m6A methylation regulates multiple stages of mRNA processing, including splicing, export, decay, and translation. How m6A modification is involved in insect development is not well known. We used the red flour beetle, Tribolium castaneum, as a model insect to identify the role of m6A modification in insect development. RNA interference (RNAi)-mediated knockdown of genes coding for m6A writers (m6A methyltransferase complex, depositing m6A to mRNA) and readers (YTH-domain proteins, recognizing and executing the function of m6A) was conducted. Knockdown of most writers during the larval stage caused a failure of ecdysis during eclosion. The loss of m6A machinery sterilized both females and males by interfering with the functioning of reproductive systems. Females treated with dsMettl3, the main m6A methyltransferase, laid significantly fewer and reduced-size eggs than the control insects. In addition, the embryonic development in eggs laid by dsMettl3 injected females was terminated in the early stages. Knockdown studies also showed that the cytosol m6A reader, YTHDF, is likely responsible for executing the function of m6A modifications during insect development. These data suggest that m6A modifications are critical for T. castaneum development and reproduction.