MicroRNA-mediated regulation of lipid metabolism in virus-infected Emiliania huxleyi

The consequences of viral infection on protists

Protists encompass a vast widely distributed group of organisms, surpassing the diversity observed in metazoans. Their diverse ecological niches and life forms are intriguing characteristics that render them valuable subjects for in-depth cell biology studies. Throughout history, viruses have played a pivotal role in elucidating complex cellular processes, particularly in the context of cellular responses to viral infections. In this comprehensive review, we provide an overview of the cellular alterations that are triggered in specific hosts following different viral infections and explore intricate biological interactions observed in experimental conditions using different host-pathogen groups.

Let-7a-5p Regulates Animal Lipid Accumulation by Targeting Srebf2 and Thbs1 Signaling

Recently, the trend of obesity is becoming increasingly prevalent, and the underlying pathogenesis of obesity is complex and needs to be researched further. In this study, we report a decreased expression of let-7a-5p in the white adipose tissue (WAT) of animals with obesity. Using the RNA oligo, let-7a-5p over-expression or suppression-expression is achieved, impacting the proliferation and differentiation of preadipocytes in vitro. Srebf2 mechanistically interacts with the metabolic effect of let-7a-5p and participates in lipid accumulation by regulating Srebf2 downstream signaling. Moreover, let-7a-5p binds to Thbs1 to interact with the PI3K-AKT-mTOR pathway, down-regulating the phosphorylation levels of AKT, mTOR, and S6K1 to decrease lipid accumulation. In conclusion, our study highlights the physiological significance of let-7a-5p in lipid accumulation and suggests that the let-7a-5p/Srebf2 and let-7a-5p/Thbs1/PI3K-AKT-mTOR axes may represent potential mechanisms for controlling lipid accumulation in obesity.

Phylogeny and genetic variations of the three genome compartments in haptophytes shed light on the rapid evolution of coccolithophores

Haptophyte algae, including coccolithophores, play key roles in global carbon cycling and ecosystem. They exhibit exceptional morphological and functional diversity. However, their phylogeny is mostly based on short markers and genome researches are always limited to few species, hindering a better understanding about their evolution and diversification. In this study, by assembling 69 new plastid genomes, 65 new mitochondrial genomes, and 55 nuclear drafts, we systematically analyzed their genome variations and built the most comprehensive phylogenies in haptophytes and Noelaerhabdaceae, with the latter is the family of the model coccolithophore Emiliania huxleyi. The haptophyte genomes vary significantly in size, gene content, and structure. We detected phylogenetic incongruence of Prymnesiales between genome compartments. In Noelaerhabdaceae, by including Reticulofenestra sessilis and a proper outgroup, we found R. sessilis was not the basal taxon of this family. Noelaerhabdaceae strains have very similar genomic features and conserved sequences, but different gene content and dynamic structure. We speculate that was caused by DNA double-strand break repairs. Our results provide valuable genetic resources and new insights into the evolution of haptophytes, especially coccolithophores.

Identification and Verification of Candidate miRNA Biomarkers with Application to Infection with Emiliania huxleyi Virus

The interactions of Emiliania huxleyi and its specific lytic virus (EhV) have a profound influence on marine biogeochemical carbon-sulfur cycles and play a prominent role in global climate change. MicroRNAs (miRNAs) have emerged as promising candidates with extensive diagnostic potential due to their role in virus-host interactions. However, the application of miRNA signatures as diagnostic markers in marine viral infection has made limited progress. Based on our previous small-RNA sequencing data, one host miRNA biomarker that is upregulated in early infection and seven viral miRNA biomarkers that are upregulated in late infection were identified and verified using qRT-PCR and a receiver operating characteristic curve analysis in pure culture, mixed culture, and natural seawater culture. The host ehx-miR20-5p was able to significantly differentiate infection groups from the control in the middle (24 h post-infection, hpi) and late infection (48 hpi) phases, while seven virus-derived miRNA biomarkers could diagnose the early and late stages of EhV infection. Functional enrichment analysis showed that these miRNAs participated in numerous essential metabolic pathways, including gene transcription and translation, cell division-related pathways, protein-degradation-related processes, and lipid metabolism. Additionally, a dual-luciferase reporter assay confirmed the targeted relationship between a viral ehv-miR7-5p and the host dihydroceramide desaturase gene (hDCD). This finding suggests that the virus-derived miRNA has the ability to inhibit the host sphingolipid metabolism, which is a specific characteristic of EhV infection during the late stage. Our data revealed a cluster of potential miRNA biomarkers with significant regulatory functions that could be used to diagnose EhV infection, which has implications for assessing the infectious activity of EhV in a natural marine environment.