Lifestyles of plant viruses

Abstract

The vast majority of well-characterized eukaryotic viruses are those that cause acute or chronic infections in humans and domestic plants and animals. However, asymptomatic persistent viruses have been described in animals, and are thought to be sources for emerging acute viruses. Although not previously described in these terms, there are also many viruses of plants that maintain a persistent lifestyle. They have been largely ignored because they do not generally cause disease. The persistent viruses in plants belong to the family Partitiviridae or the genus Endornavirus. These groups also have members that infect fungi. Phylogenetic analysis of the partitivirus RNA-dependent RNA polymerase genes suggests that these viruses have been transmitted between plants and fungi. Additional families of viruses traditionally thought to be fungal viruses are also found frequently in plants, and may represent a similar scenario of persistent lifestyles, and some acute or chronic viruses of crop plants may maintain a persistent lifestyle in wild plants. Persistent, chronic and acute lifestyles of plant viruses are contrasted from both a functional and evolutionary perspective, and the potential role of these lifestyles in host evolution is discussed.

Figure 1.

Phylogenetic relationships of partitvirus RdRps. Amino acid sequences for partitivirus RdRps were downloaded from GenBank, aligned with MAFFT and alignments were thoroughly edited in Mesquite (Maddison & Maddison 2009). Aligned sequences were analysed using MrBayes (Ronquist & Huelsenbeck 2003) under a fixed rate model, with 10 000 generations. The consensus tree after burn-in was displayed in Mesquite. Viruses names are coloured by the host group: green, plant host; pink, basidiomycete host; turquoise, ascomycete host. A nearly identical tree was obtained with maximum parsimony (not shown).