RNAi-mediated resistance to yellow mosaic viruses in soybean targeting coat protein gene

In this genomic era, soybean has entrenched genomic database which offer an extensive scope for improvement through genetic manipulation, although demand for transgenics soybean with better production and enhanced quality has been handicapped due to Mungbean yellow mosaic India virus (MYMIV) belonging to the genus Begomovirus. MYMIV is a causative agent of yellow mosaic disease that has been emerged as a threat to the cultivation of bean family in India. In this study, transgenic soybean plants were generated using the intron-spliced hairpin construct encoding the coat protein sequence of MYMIV in the control of 35S promoter and ocs terminator. Integration of coat protein gene in independently transformed plants was confirmed by PCR and Southern hybridization where one transgenic line of coat protein-event A, two transgenic lines of coat protein-event B, and two transgenic lines from the coat protein-event C showed gene hybridization. Inoculation was performed on T₁ seedlings of transgenic and non-transgenic plants where the viral replicative DNA level was assessed for ten plants and a quality concentration of viral replicative form was seen in the transgenic lines. Northern blot analysis detects siRNA in the transgenic line 2 of event A, line 5 and 6 of event B, as well as line 9 and 10 from event C inoculated with viruliferous whiteflies and a high level of siRNA (21–22 nt) was observed in the transgenic line 2 and line 10 which corroborated by the non-detectable level of viral replicative DNA and low concentration of viral transcript for replication as estimated in qRT-PCR. Results obtained in this study confirmed the transgene construct can be used to develop resistance against begomoviruses in soybean and other crops, as it targets the most conserved domain governing whitefly transmission.