Phylogenetic analyses of an isolate obtained from potato in 1985 revealed potato virus X was introduced to China via multiple events

Abstract

Potato virus X (PVX) is one of the most common plant viruses that cause great economic losses to solanaceous plants. We have previously reported the complete genomic sequence of the 2006 Chinese potato isolate FX21 and demonstrated that PVX isolates cluster into two groups: Eurasia and America. Here, we present the complete genomic sequence of one PVX isolate collected from potato in 1985 (PVX-1985). The genome of PVX-1985 is identical to that of FX21 in length and has the same genomic structure. PVX-1985, which like FX21 fell within the Eurasia group, clustered together with isolates from Europe, whereas FX21 clustered together with isolates of primarily Asian origin. Phylogenetic analyses of the complete genomic sequences and of CP gene sequences showed that Chinese PVX isolates have different origins and were introduced via multiple events. Though all the open reading frames of PVX are under negative/purifying selection, the central region of RNA-dependent RNA polymerase is under positive/diversifying selection.

Molecular characterization and field survey of Iranian potato virus X isolates

“…According to the results of this study and those of Yu et al [25,26] different selection pressure is operating on different genes of PVX, and the ORF encoding RdRp is under the highest selection pressure. Therefore, the RdRp ORF of 27 PVX complete genome were further divided into three parts as described by Yu et al [26] and their dN/dS values separately were calculated. Unlike previous studies by Yu et al, 2010 our results indicated the dN/dS values for three parts of genome were \1, despite the fact that RdRp-B was higher than RdRp-A and RdRp-C.…”

“…The Iranian isolates are part of clade I with clade II representing isolates from South America. Interestingly, the two isolates (PVX 2.7 and PVX 2.7b) from U.S.A are part of clade I and hence clearly indicates that the isolates from North America are distinct from those in the southern America contradicting the previous suggestion of two distinct lineages of PVX, Eurasia and America [3,13,25,26].…”

“…ORF5 encodes the capsid protein (CP) with an estimated molecular mass of 25 kDa and plays an significant role in cell-to-cell movement of PVX particles and translational regulation of the PVX RNA genome [10,14]. The CP gene is widely used for identification and classification of PVX isolates [3,25,26].…”

Population genetic analysis of potato virus X based on the CP gene sequence

“…Previous studies have shown that the PVX isolates can be classified into two lineages, Eurasia and America, which correspond to their geographical origin [22,24,44,45]. PVX is well-known as a model for understanding pathogen-host interaction [4,14,20] and efforts in recent years have established good knowledge about genetic basis of resistance and the genetic system controlling behavior of the pathogen [2,21,32].…”

“…Although there are several studies on phylogenetic analysis, selection pressure operating on different genes, and estimation of genetic variability on different coding regions of PVX [24,44,45], there still remained a lack of information on evolutionary constraints for the two virus lineages, molecular diversity patterns, population differentiation and recombination event(s). Here, population genetic analysis of PVX isolates from different countries was done based on the CP sequences because conserved nature of the CP gene makes it a suitable candidate for such studies.…”