The article discusses the rapid advancements in understanding the evolution and genome structure of RNA viruses, particularly focusing on the Paramyxoviridae and Coronavirus families. It highlights the importance of sequencing in elucidating evolutionary relationships and the organization of viral genomes. Key points include: 1. **Paramyxoviridae**: - The family includes viruses like Newcastle disease virus (NDV), Sendai virus, and human parainfluenza viruses (PIVs). - These viruses use multiple reading frames within the V/P gene to produce multiple protein products. - A new mechanism of translational frame-shifting is described, where non-templated G residues are added to shift the reading frame, producing proteins like P, C, V, and D. 2. **Coronaviruses**: - Coronaviruses have large genomes and produce up to seven subgenomic mRNAs. - These mRNAs are transcribed from the minus strand of the genome and can replicate independently. - The replication strategy involves leader-primed transcription and the use of minus-strand copies of mRNAs. 3. **Plant and Animal Viruses**: - Many plant viruses have counterparts in animal viruses, sharing genome organization and transcription strategies. - Examples include plant comoviruses and animal picornaviruses, as well as plant tobamoviruses and animal togaviruses. - The relationship between these viruses suggests a common ancestor and the evolution of specific genes through recombination. 4. **Bunyaviridae**: - This family includes viruses with segmented negative-strand RNA genomes. - The Bunyaviridae have three genome segments, with different strategies for gene expression. - The tospoviruses, with a morphology similar to bunyaviruses, have been classified as a genus of Bunyaviridae. 5. **Conclusion**: - RNA viruses have evolved from a small number of protoviruses and have diversified through divergent evolution and recombination. - They have developed mechanisms to expand coding capacity and regulate gene expression, such as translating multiple reading frames and producing subgenomic mRNAs. The article emphasizes the importance of genomic sequencing in understanding the complex dynamics of RNA viruses and their evolutionary history.The article discusses the rapid advancements in understanding the evolution and genome structure of RNA viruses, particularly focusing on the Paramyxoviridae and Coronavirus families. It highlights the importance of sequencing in elucidating evolutionary relationships and the organization of viral genomes. Key points include: 1. **Paramyxoviridae**: - The family includes viruses like Newcastle disease virus (NDV), Sendai virus, and human parainfluenza viruses (PIVs). - These viruses use multiple reading frames within the V/P gene to produce multiple protein products. - A new mechanism of translational frame-shifting is described, where non-templated G residues are added to shift the reading frame, producing proteins like P, C, V, and D. 2. **Coronaviruses**: - Coronaviruses have large genomes and produce up to seven subgenomic mRNAs. - These mRNAs are transcribed from the minus strand of the genome and can replicate independently. - The replication strategy involves leader-primed transcription and the use of minus-strand copies of mRNAs. 3. **Plant and Animal Viruses**: - Many plant viruses have counterparts in animal viruses, sharing genome organization and transcription strategies. - Examples include plant comoviruses and animal picornaviruses, as well as plant tobamoviruses and animal togaviruses. - The relationship between these viruses suggests a common ancestor and the evolution of specific genes through recombination. 4. **Bunyaviridae**: - This family includes viruses with segmented negative-strand RNA genomes. - The Bunyaviridae have three genome segments, with different strategies for gene expression. - The tospoviruses, with a morphology similar to bunyaviruses, have been classified as a genus of Bunyaviridae. 5. **Conclusion**: - RNA viruses have evolved from a small number of protoviruses and have diversified through divergent evolution and recombination. - They have developed mechanisms to expand coding capacity and regulate gene expression, such as translating multiple reading frames and producing subgenomic mRNAs. The article emphasizes the importance of genomic sequencing in understanding the complex dynamics of RNA viruses and their evolutionary history.