Silencing of one copy of the translation initiation factor eIFiso4G in Japanese plum (Prunus salicina) impacts susceptibility to Plum pox virus (PPV) and small RNA production

Abstract

BackgroundIn plants, host factors encoded by susceptibility (S) genes are indispensable for viral infection. Resistance is achieved through the impairment or the absence of those susceptibility factors. Many S genes have been cloned from model and crop species and a majority of them are coding for members of the eukaryotic translation initiation complex, mainly eIF4E, eIF4G and their isoforms. The aim of this study was to investigate the role of those translation initiation factors in susceptibility of stone fruit species to sharka, a viral disease due to Plum pox virus (PPV).ResultsFor this purpose, hairpin-inducing silencing constructs based on Prunus persica orthologs were used to generate Prunus salicina (Japanese plum) 4E and 4G silenced plants by Agrobacterium tumefaciens-mediated transformation and challenged with PPV. While down-regulated eIFiso4E transgenic Japanese plums were not regenerated in our conditions, eIFiso4G11-, but not the eIFiso4G10-, silenced plants displayed durable and stable resistance to PPV. We also investigated the alteration of the si- and mi-RNA profiles in transgenic and wild-type Japanese plums upon PPV infection and confirmed that the newly generated small interfering (si) RNAs, which are derived from the engineered inverted repeat construct, are the major contributor of resistance to sharka.ConclusionsOur results indicate that S gene function of the translation initiation complex isoform is conserved in Prunus species. We discuss the possibilities of using RNAi silencing or loss-of-function mutations of the different isoforms of proteins involved in this complex to breed for resistance to sharka in fruit trees.

The Role of Italy in the Use of Advanced Plant Genomic Techniques on Fruit Trees: State of the Art and Future Perspectives

“…Due to the lack of R genes to Sharka disease in peach [ 183 ], CRISPR/Cas9 is being applied to address recessive resistance to this detrimental virosis, targeting susceptibility genes [ 184 , 185 ]. Silencing of eIFiso4E in P. domestica and eIFiso4G11 in P. salicina , coding for members of the eukaryotic initiation complex eIFiso4F involved in Plum pox virus infection, resulted in resistant plants [ 186 ]. Different regions of eIFiso4E are being targeted with a different single sgRNA with the intent of obtaining an allelic series of mutations [ 187 , 188 ].…”

Gene Editing inPrunusSpp.: The Challenge of Adapting Regular Gene Transfer Procedures for Precision Breeding

“…Interestingly, these materials have led to one of the few studies in woody plant species in which small RNAs have been demonstrated to be transported from rootstock to scion, making 'Emperor Francis' scions become resistant to PNRSV [9]. Finally, in 2019, we developed a transgenic Japanese plum tree exploiting the RNAi methodology to target a gene linked to Plum pox virus (PPV)-susceptibility, thus generating individuals resistant to PPV [10].…”

Deciphering Prunus Responses to PPV Infection: A Way toward the Use of Metabolomics Approach for the Diagnostic of Sharka Disease

“…Rubio et. [ 30 ] attempted to determine the role of transcriptional initiation factors in the PPV infection of Japanese plums ( Prunus salicina ). In fact, a mutation in these genes confers a resistance to infection by viruses from the Tombusviridae, Bromoviridae, Waikaviridae , and Potyviridae families.…”

“…Figure 6. Model of eIFiso4F-mediated susceptibility to PPV in diploid plums from Rubio et al[30]. The silencing of eIFiso4G, a translation initiation complex, prevents the development of the virus in the host but does not prevent the development of the plant.…”