RESUMO
BACKGROUND: In 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). RESULTS: For 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. CONCLUSIONS: Our 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.
Assuntos
Resistência à Doença/genética , Fatores de Iniciação em Eucariotos/metabolismo , Doenças das Plantas/imunologia , Vírus Eruptivo da Ameixa/fisiologia , Prunus/genética , Fatores de Iniciação em Eucariotos/genética , Frutas/genética , Frutas/imunologia , Frutas/virologia , Doenças das Plantas/virologia , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Plantas Geneticamente Modificadas , Isoformas de Proteínas , Prunus/imunologia , Prunus/virologia , Interferência de RNA , RNA de Plantas/genética , RNA Interferente Pequeno/genética , ÁrvoresRESUMO
Background: Small ribonucleic acids represent an important repertoire of mobile molecules that exert key roles in several cell processes including antiviral defense. Small RNA based repertoire includes both small interfering RNA (siRNA) and microRNA (miRNA) molecules. In the Prunus genus, sharka disease, caused by the Plum pox virus (PPV), first occurred on European plum (Prunus domestica) and then spread over among all species in this genus and thus classified as quarantine pathogen. Next-generation sequencing (NGS) was used for the study of siRNA/miRNA molecules; however, NGS relies on adequate extraction protocols. Currently, knowledge of PPV-Prunus interactions in terms of siRNA populations and miRNA species is still scarce, and siRNA/miRNA extraction protocols are limited to species such as peach, almond, and sweet cherry. Results: We describe a reliable procedure for siRNA/miRNA purification from Prunus salicina trees, in which previously used protocols did not allow adequate purification. The procedure was based on a combination of commercially available RNA purification kits and specific steps that yielded high quality purifications. The resulting molecules were adequate for library construction and NGS, leading to the development of a pipeline for analysis of both siRNAs and miRNAs in the PPVP. salicina interactions. Results showed that PPV infection led to altered siRNA profiles in Japanese plum as characterized by decreased 24-nt and increased 21- and 22-nt siRNAs. Infections showed miR164 and miR160 generation and increased miR166, miR171, miR168, miR319, miR157, and miR159. Conclusion: We propose this protocol as a reliable and reproducible small RNA isolation procedure for P. salicina and other Prunus species.