Study On Interaction Between Rice Black-Streaked DWARF Virus (RBSDV) P8 And OsGID1,a Factor Of Hostrice Plant

Plant viruses are intracellular pathogens and just encode a few of viral proteins. It is required for the completion of their life cycles to take advantage of factors fromhost plants. Viral proteins, including capsid proteins, replication-associated proteins, movement proteins, and viral suppressors of gene silencing, are generally involved in viral multiplication, movement and transmission and induce a series of symptoms, such as developmental abnormalities, chlorosis, and necrosis, by interacting with host factors. Therefore,unravelling the interactionsof viral proteins with their host factorswould be helpful to understanding the viral pathogenic mechanism and developing the new strategies for viral disease control.The pathogen of rice black-streaked dwarf disease is Rice black-streaked dwarf virus (RBSDV),which is a recognized member of the genus Fijivirus, family Reoviridae and transmitted by the small brown planthopper (Laodelphax striatellus). RBSDV-infected rice plants are usually stunted with more tillering, dark leaves, and waxy white to black galls along the veins on the underside of leaf blades and on the outer surface of sheaths and culms. The virus contain 10 linear genomic segments of double-stranded RNA (dsRNA), named S1-10. The complete genomesequences of RBSDV have been determined, in which S8 encode astructural proteinof core viral particles with a conserved NTP-binding motif. However, interaction between RBSDV p8 and host factors still remains unknown.In this study, RBSDVp8 was used as a bait to screening a rice cDNA library in a yeast two-hybrid. Three prey proteins were found to be candidate host factors interacted with RBSDV P8.The full-length coding region of a candidate host factor, Gibberellin-insensitive dwarf protein 1 (OsGID1), was cloned for further study. The results from yeast two-hybrid (YTH), bimolecular fluorescencecomplement (BiFC), and pull-down assays consistently indicated a strong interaction between RBSDV p8 and host factor OsGIDl in vivo and vitro. Assays of subcellular localization inepidermal cells of N. benthamiana leaves showed that RBSDV p8 and OsGIDl can separately accumulatedin both cytoplasm and nucleus. Co-localization of RBSDV p8 and OsGID1 in both cytoplasm and nucleussupported their interaction.Moreover,the region (amino acids 339-489) of p8 was found to be crucial for its interaction with OsGID1 in yeast two-hybrid assays. In addition, RBSDV p8 gene was introduced into Arabidopsis by the method of floraldip and 50 transgenic lines of T1 generation with RBSDV p8 gene were obtained.The transgenic plants overexpressing RBSDV P8 were found to display significantly dwarf phenotype when compared with the wild type plants and blank control plants of Arabidopsis. These results suggested that the strong interaction between RBSDV p8 and OsGID1 could interfere with the GA-mediated signal transduction pathway and thus lead to the dwarf phenotype of plants.