Nucleotide sequence-homology-independent breakdown of transgenic resistance by more virulent virus strains and a potential solution.

Yi-Jung Kung, Bang-Jau You, Joseph A J Raja, Kuan-Chun Chen, Chiung-Huei Huang, Huey-Jiunn Bau, Ching-Fu Yang, Chung-Hao Huang, Chung-Ping Chang, Shyi-Dong Yeh

Scientific reports 2015 Apr 27

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Controlling plant viruses by genetic engineering, including the globally important Papaya ringspot virus (PRSV), mainly involves coat protein (CP) gene mediated resistance via post-transcriptional gene silencing (PTGS). However, the breakdown of single- or double-virus resistance in CP-gene-transgenic papaya by more virulent PRSV strains has been noted in repeated field trials. Recombination analysis revealed that the gene silencing suppressor HC-Pro or CP of the virulent PRSV strain 5-19 is responsible for overcoming CP-transgenic resistance in a sequence-homology-independent manner. Transient expression assays using agro-infiltration in Nicotiana benthamiana plants indicated that 5-19 HC-Pro exhibits stronger PTGS suppression than the transgene donor strain. To disarm the suppressor from the virulent strain, transgenic papaya lines were generated carrying untranslatable 5-19 HC-Pro, which conferred complete resistance to 5-19 and other geographic PRSV strains. Our study suggested the potential risk of the emergence of more virulent virus strains, spurred by the deployment of CP-gene-transgenic crops, and provides a strategy to combat such strains.

Citation

Yi-Jung Kung, Bang-Jau You, Joseph A J Raja, Kuan-Chun Chen, Chiung-Huei Huang, Huey-Jiunn Bau, Ching-Fu Yang, Chung-Hao Huang, Chung-Ping Chang, Shyi-Dong Yeh. Nucleotide sequence-homology-independent breakdown of transgenic resistance by more virulent virus strains and a potential solution. Scientific reports. 2015 Apr 27;5:9804