Molecular characterization of the mild Soil-borne wheat mosaic virus-Pol1 isolate

Abstract

Soil-borne wheat mosaic virus is the causal agent of leaf mosaic symptoms in cereals. The low virulence and limited propagation in infected plant tissues of a Polish isolate (SBWMV-Pol1) differ from the characteristics of other known isolates. The research aimed to clarify the effects of nucleotide sequence variability on the observed biological differences among the following three isolates: SBWMV-Pol1, SBWMV-Heddesheim and SBWMV-SH1-3. Because of insufficient information regarding reference isolates, the RNAs from German isolates were sequenced for subsequent comparative analyses. Partial RNA1 and nearly complete RNA2 sequence for the Polish and two German isolates were obtained. Comparative analysis of received sequences with those of the corresponding fragments from other SBWMV isolates deposited in the GenBank database was carried out. The results of examined isolates confirmed: complete amino acid and nucleotide sequence identities for the replicase (REP) fragment 2 and the cysteine-rich protein, as well as complete amino acid and partial nucleotide sequence identities for the REP fragment 1 (99.4–100%) and the coat protein (87 − 100%), respectively. Differences in the amino acid and nucleotide sequences of the movement protein (MP) (98.7–99.6% and 99.5% sequence identities, respectively) were also detected. The sequence of the -Pol1 isolate was very similar to those of the -SH1-3 and -Heddesheim isolates, with only one and three non-synonymous point mutations in the MP gene, respectively. Nevertheless, there were obvious differences in the biological properties of these isolates. Point mutations within the MP gene may have considerable consequences for symptom development.