Using genomics, evolutionary biologists test several hypotheses on the origin of viruses. New evidence suggests they may have emerged more times than previously thought.

Flori et al. establish high-resolution and generalizable immunofluorescence in cultured and environmental diatoms, thanks to 4-fold cryo-expansion microscopy. This represents a step-change for compara...

An exploration of the viromes of haloarchaea and their ultra-small DPANN symbionts reveals plasmid-derived satellites of viruses from both archaeal groups, highlighting the complexity of nested symbio...

Defense-associated reverse transcriptases (DRTs) employ diverse and distinctive mechanisms of cDNA synthesis to protect bacteria against viral infection. However, much of DRT family diversity remains ...

Cells must coordinate DNA segregation with cytokinesis to ensure that each daughter cell inherits a complete genome. Here, we explore how DNA segre...

On Tuesday, President Donald Trump announced that the U.S. military had killed six people in a strike on a boat that, Trump said, was “trafficking narcotics.”

Giant viruses challenge traditional boundaries of virology with their large particle sizes, complex genomes, and unique replication strategies. Yet, despite its 750 nm diameter and incorporation of do...

Giant double-stranded DNA viruses infecting microalgae often interact with polinton-like viruses (PLVs), yet their dynamics within natural hosts remain poorly understood. Here, we report the isolation of a new Tetraselmis striata giant virus (Allomimiviridae) from Mediterranean coastal waters, which we designate Oceanusvirus lionense (TetV-2). From the same sample, we co-isolated a PLV, Tsa-S2b, that replicates concomitantly with TetV-2. Remarkably, TetV-2 infection also reactivates at least two additional PLVs integrated into the host genome. We show that these PLVs exert a virophage-like effect, reducing the fitness of the giant virus. Comparative genomics reveals that these virophagic PLVs are related to the autonomous lytic PLV TsV-N1, sharing structural but not replication-associated genes. This newly described pathosystem provides a unique model to investigate the evolution of PLVs and the parasitic mechanisms underlying virophage-giant virus interactions. ### Competing Interest Statement The authors have declared no competing interest. European FEDER Fund, project 1166-39417 Excellence Initiative of Aix-Marseille University – A*MIDEX

VAD is a Viral AlphaFold Database of protein monomers and homodimers from viruses infecting hosts across the tree of life.

In contrast to living organisms, viruses were long thought to lack protein synthesis machinery and instead depend on host factors to translate viral transcripts. Here, we discover that giant DNA virus...