Diversity and evolution of the ribovirian class Stelpaviricetes.

RdRP phylogeny in Stelpaviricetes reveals 103 putative families, with most sharing an astrovirus-like genome architecture and a common astrovirus-like ancestor.

• Why it matters: Metatranscriptome mining is uncovering ribovirus diversity, but the evolutionary relationships and likely ancestral genome features within Stelpaviricetes remain unclear.
• What they did: The authors built an order-specific RdRP Hidden Markov Model set to identify 103 putative families, then inferred genome evolution from RdRP tree topology and domain gains/losses.
• The result: They infer an astrovirus-like common ancestor for Stelpaviricetes; Patatavirales gained papain-like protease and superfamily 2 helicase with filamentous capsids, while Hypofuvirales retained helicase/protease but lost capsids, leaving host assignments mostly unresolved.

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