Evolutionarily conserved grammar rules viral factories of amoeba-infecting members of the hyperdiverse phylum.

Despite sharing fewer than 10 core genes, the hyperdiverse phylum (ranging from poxviruses to giant viruses) universally assembles viral factories (VFs) resembling biomolecular condensates. Regardless, it is unclear how these viruses achieve such a level of functional conservation without clear conserved genetic information. We demonstrate that the VFs produced by amoeba-infecting viruses have liquid-like properties and identify a conserved molecular grammar governing viral factory scaffold protein: charge-patterned intrinsically disordered regions that drive phase separation independently of sequence homology. This grammar predicts functional scaffold proteins across the 15 viral families, revealing evolutionary constraints invisible to sequence or structural analysis. Strikingly, VFs exhibit subcompartmentalization analogous to nuclei, segregating transcription and mRNA processing (inner condensates) from replication (interphase zones) and translation (host cytoplasm). Our work establishes phase separation as a fundamental organizational principle bridging extreme genomic diversity, explaining how biological complexity emerges without gene conservation. This grammar is likely also conserved in non-amoeba-infecting members of the phylum and thus may represent a primordial solution for organelle-like organization, with broad implications for antiviral targeting.