Genome characterization, infectivity assays of in vitro and in vivo infectious transcripts of soybean yellow mottle mosaic virus from India reveals a novel short mild genotype

Abstract

Nucleotide sequence of a distinct soybean yellow mottle mosaic virusisolate from Vignaradiata (mungbean isolate, SYMMV-Mb) from India was determined and compared with othermembers of the family Tombusviridae. The complete monopartite single-stranded RNA genome of SYMMV-Mb consisted of 3974nt with six putative open reading frames and includes 5′ and 3′ untranslated regions of 35 and 254nt, respectively. SYMMV-Mb genome shared 75% nt sequence identity at complete genome level and 67–92% identity at all ORFs level with SYMMV Korean and USA isolates (soybean isolates) followed by CPMoV, whereas it shared very low identity with other tombusviridae members (5–41%). A full-length infectious cDNA clone of the SYMMV-Mb placed under the control of the T7 RNA polymerase and the CaMV35S promoters was generated and French bean plants on mechanical inoculation with in vitro RNA transcripts, p35SSYMMV-O4 plasmid and agroinoculation with p35SSYMMV-O4 showed symptoms typical of SYMMV-Mb infection. The infection was confirmed by DAC-ELISA, ISEM, RT-PCR and mechanical transmission to new plant species. Further testing of different plant species with agroinoculation of p35SSYMMV-O4 showed delay in symptoms but indistinguishable from mechanical sap inoculation and the infection was confirmed by DAC-ELISA, RT-PCR and mechanical transmission to new plants. The system developed here will be useful for further studies on pathogenecity, viral gene functions, plant-virus-vector interactions of SYMMV-Mb and to utilize it as a gene expression and silencing vector.