Phylogenetic Study of Two Iranian Isolates of Wheat streak mosaic virus in NIa-Pro Proteinase Coding Region

Wheat streak mosaic virus, a member of the genus Tritimovirus in the family Potyiviridae, is a destructive pathogen of cereals. In this research, NIa-Pro as one of the most important proteinase of WSMV was analyzed. For this purpose, 116 wheat symptomatic samples were collected from North Khorasan, South Khorasan and West Azarbayjan provinces and tested by ELISA. Ten ELISA positive samples were propagated by mechanical inoculation on wheat and were tested by RT-PCR using specific primers that were amplified a 732 bp fragment of full length NIa-Pro coding region in all of the 10 samples. Then, two isolates from Iran, according to their geographical properties, were selected, cloned and sequenced. In the phylogenetic analysis, two distinct groups were separated. The isolates from iran were placed in Group I and subgroup IB close to isolate from America (NC-001886). Iranian isolates formed a sub group separate from previously reported isolates from Iran (Saadat shahr) and Europe. Analysis of cleavage sites in NIa-Pro of the isolates from iran, showed that all of them were conserved in comparison to the isolates previously recorded in GenBank but some substitutions were observed at NIa-Pro motifs. AETT residues at position 121-124 were replaced by GKSH, alanine residue was replaced by Threonin at position 154 and Glutamin alanine at position 208. This research is the first analysis of NIa- pro in isolates of WSMV from Iran.