Study On The Role Of Rice Black-streaked Dwarf Virus P10 Protein And Brassinosteroids Or Auxin Pathway In The Rice-Virus Interaction

Rice black-streaked dwarf virus(RBSDV)and Rice stripe virus(RSV)are two important rice viruses.Our previous research found expressing P10 in plants made the plants more resistance to RBSDV and the closely-related southern rice black-streaked dwarf virus(SRBSDV).However,there is little research on the role of RBSDV coat protein P10 in the unrelated RSV.Therefore,we used expressing P10 transgenic rice(OEP10)to study the role of RBSDV P10 protein in RSV infection.Exogenous hormone applications and transgenic mutants were used to explore the mechanism of the roles of Brassinosteroids(BRs)and Auxin pathway in the Rice-Virus interaction.The results of this research are listed as following:1.This study mainly used indoor artificial inoculation RSV system to preliminarily confirm that the resistance of OEP10 transgenic rice to RSV was weakened.Co-infection of RBSDV and RSV was always in favor of RSV,while the infection order determined the outcome of RBSDV multiplication.According to transcriptome data and qRT-PCR of OEP10 plants,many plant defense pathways related genes,such as Salicylic acid and Jasmonic acid pathway,were suppressed.These results suggest that expressing P10 in rice affects plant defense responses that were involved in the suppression of RSV multiplication.In addition,transcriptome analysis also indicated that OEP10 plants can alter the expression of genes involved in many plant hormone pathways,including,for example,Auxin,CK and BR pathways.2.RBSDV infection making RBSDV-infected plants more sensitive to BL treatment.Here we showed that the role of both BR deficient and sensitive mutant(dlt,RI90B)were less susceptible to RBSDV.According to high-throughput sequencing,the defense hormones salicylic acid(SA)and jasmonic acid(JA)pathway were activated in RBSDV-infected BR mutant than RBSDV-infected ZH11.These results indicated that BR pathway antagonizes the JA/SA pathway in response to RBSDV infection.3.According to high-throughput sequencing,a number of class III peroxidases(OsPrx)were significantly changed and basal reactive oxygen species(ROS)level was accumulated in BR mutants(dlt,R190B).By the activity of OsPrx and NBT staining assay suggested the ROS burst were activated in BR mutants(dlt,RI90B).The activity of OsPrx in SHAM-treated BR mutants showed no significantly difference with that in SHAM-treated WT plants(Salicylhydroxamic acid(SHAM)as a inhibitor of peroxidase).The SHAM-treated rice plants were inoculated with RBSDV,and found SHAM-treatment could increase rice susceptibility to viral infection.The expression of OsPrx genes was significantly less in BL-treated seedlings than in mock plants.BR pathway directly modulated the expression of OsPrx.These results suggested that peroxidase-dependent ROS accumulation played important roles in BR-mediated susceptibility to RBSDV infection.4.The auxin signalling pathway was markedly decreased following infection of RBSDV.The auxin signalling mutants(35S:miR1393a,OsIAA20 and OsIAA31)were susceptibility to RBSDV infection.qRT-PCR results indicated that the JA pathway related OsPR genes activated by RBSDV infection were repressed when auxin signalling was disrupted.The JA pathway may be part of the auxin signalling-mediated rice defence against RBSDV.5.qRT-PCR showed that the OsRboh(B,D)genes ang the accumulation of ROS were inhibited in the auxin mutant.Chemicals 2,4-D,NAA treatment revealed that the OsRboh(B,D)genes were significantly activated.NBT staining showed that the auxin pathway positively regulates OsRboh-mediated ROS accumulation.RBOH activity inhibitor DPI treatment rice leaves significantly inhibited the expression of OsRboh(B,D)gene.The viral symptoms and the RBSDV RNA levels were much greater in DPI-treated plants than in the untreated controls.These results suggest that OsRboh-mediated ROS accumulation plays an important role in rice resistance to RBSDV infection.In summary,our results demonstrate that OEP10 transgenic rice was susceptible to RSV,which might due to the expressing P10 in plants significantly suppressed the expression of rice defense-related genes in SA,JA,BR and auxin pathways.The BR pathway antagonizes JA,SA and ROS pathway to mediate rice susceptibility to RBSDV infection.The auxin signaling pathway played positive roles in rice defence against RBSDV infection.