VIRAL EVOLUTION AND INSECTS AS A POSSIBLE VIROLOGICAL TURNING TABLE

Three lines of observation demonstrate the role of arthropods in trans mission and evolution of viruses. a) Recent outbreaks of viruses from their niches took place and insects have played a major role in propag ating the viruses. b) Examination of the list of viral families and th eir hosts shows that many infect invertebrates (I) and vertebrates (V) or (I) and plants (P) or all kingdoms (VIPs). This notion holds true irrespective of the genome type. At first glance the argument seems to be weak in the case of enveloped and non-enveloped RNA viruses with s ingle-stranded (ss) segmented or non-segmented genomes of positive (+) or negative polarity. Here, there are several families infecting V or P only; no systematic relation to arthropods is found. c) In the non- enveloped plant viruses with ss RNA genomes there is a strong tendency for segmentation and individual packaging of the genome pieces. This is in contrast to ss+ RNA animal viruses and can only be explained by massive transmission by seed or insects or both, because individual pa ckaging necessitates a multihit infection. Comparisons demonstrate rel ationships in the nonstructural proteins of double-stranded and ss+ RN A viruses irrespective of host range, segmentation, and envelope. Simi lar conclusions apply for the negative-stranded RNA viruses. Thus, vir al supergroups can be created that infect V or P and exploit arthropod s for infection or transmission or both. Examples of such relationship s and explanations for viral evolution are reviewed and the arthropod orders important for cell culture are given.