Molecular evolution of Turnip mosaic virus: evidence of host adaptation, genetic recombination and geographical spread

Abstract

Turnip mosaic virus (TuMV), a species of the genus Potyvirus, occurs worldwide. Seventy-six isolates of TuMV were collected from around the world, mostly from Brassica and Raphanus crops, but also from several non-brassica species. Host tests grouped the isolates into one or other of two pathotypes ; Brassica (B) and Brassica-Raphanus (BR). The nucleotide sequences of the first protein (P1) and coat protein (CP) genes of the isolates were determined. One-tenth of the isolates were found to have anomalous and variable phylogenetic relationships as a result of recombination. The 5h-terminal 300 nt of the P1 gene of many isolates was also variable and phylogenetically anomalous, whereas the 380 nt 3h terminus of the CP gene was mostly conserved. Trees calculated from the remaining informative parts of the two genes of the non-recombinant sequences by neighbour-joining, maximum-likelihood and maximum-parsimony methods were closely similar, and so these parts of the sequences were concatenated and trees calculated from the resulting 1150 nt. The isolates fell into four consistent groups ; only the relationships of these groups with one another and with the outgroup differed. The ' basal-B ' cluster of eight B-pathotype isolates was most variable, was not monophyletic, and came from both brassicas and non-brassicas from southwest and central Eurasia. Closest to it, and forming a monophyletic subgroup of it in most trees, and similarly variable, was the ' basal-BR ' group of eight BR pathotype Eurasian isolates. The third and least variable group, the ' Asian-BR ' group, was of 22 BR-pathotype isolates, all from brassicas, mostly Raphanus, and all from east Asia mostly Japan. The fourth group of 36 isolates, the ' world-B ' group, was from all continents, most were isolated from brassicas and most were of the B-pathotype. The simplest of several possible interpretations of the trees is that TuMV originated, like its brassica hosts, in Europe and spread to the other parts of the world, and that the BR pathotype has recently evolved in east Asia.

An attempt to identify recombinants between two sobemoviruses in doubly infected oat plants

“…Spatial separation patterns with very few cells expressing both viruses have been documented for different potyvirus species -PPV, TVMV and Clover yellow vein virus (CIYVV) (Dietrich and Maiss, 2003). However, there is substantial evidence for intra-and interspecific recombination between potyviruses derived from sequencing and phylogenetic analysis of natural virus populations (Bousalem et al, 2000;Cervera et al, 1993;Chare and Holmes, 2006;Desbiez and Lecoq, 2004;Fanigliulo et al, 2005;Ohshima et al, 2002;Tan et al, 2004;Zhong et al, 2005).…”

“…The recombination potential of TBSV, Turnip mosaic virus (TuMV), Yam mosaic virus (YMV) and BMV has been shown to depend on the host (Bousalem et al, 2000;Desvoyes and Scholthof, 2002;Dzianott and Bujarski, 2004;Ohshima et al, 2002). Screening the recombination efficiency of TBSV using a yeast single-knockout library revealed that host genes involved in RNA degradation were suppressing the generation of new viral RNA recombinants.…”

Molecular characterization of coat protein gene of Garlic common latent virus isolates from India: an evidence for distinct phylogeny and recombination

“…The five Indian isolates were grouped together with K2 isolate of South Korea and GCLV-BZL isolate of Brazil. On the basis of CP gene sequences, isolates of various virus species, such as, Cucumber mosaic virus, Prunus necrotic ringspot virus, Turnip mosaic virus, Chrysanthemum virus B (CVB), Peanut stunt virus, etc, have been grouped into 2-4 sub-groups [11][12][13][14][15][16][17]. In our study phylogenetic analysis of the CP revealed the distinct clustering pattern based on geographic origin of the GarCLV isolates.…”

New host records and new host family range forTurnip mosaic virusin New Zealand

“…in New Zealand aligned within the world-B group (Ohshima et al 2002). The partial 3 -terminus region sequence of the TuMV amplicons obtained in this study aligned with TuMV isolates detected from hosts other than Brassica spp., which also belongs to the world-B group (Tomimura et al 2004).…”

“…1d) as reported here. TuMV has the ability to form recombinants which are widespread and can lead to emerging TuMV isolates with new biological properties (Ohshima et al 2002;Tomimura et al 2004). An increase in the number of hosts infected by TuMV in New Zealand is expected.…”