Mechanism Of NF-YA Transcription Factor Suppress Jasmonic Acid Pathway And Facilitate Viral Infection In Rice

Plants need defenses against various biotic and abiotic challenges from the environment to maintain their own growth and reproduction.Plant viruses are one of the important pathogens in nature,which are harmful to plant growth and development.There are many kinds of plant viruses and most of them are transmitted by insect,it is difficult to prevent and control them.The plant diseases caused by plant viruses inflict serious challenges to crop safety.Therefore,the exploration of plant antiviral genes will be beneficial to reveal the mechanism of plant disease resistance,help us understand the process of game between plants-viruses,and also provide a new theoretical basis for green prevention and control of viral diseases.Rice is one of the main economic food crops in the world,its sustainable development has been seriously affected by rice viruses.Rice stripe virus(RSV)belongs to the genus Tenuivirus,and Southern rice black-streaked dwarf virus(SRBSDV)is classified in the genus Fijivirus,which are two important viruses that are mainly harmful to rice.Nuclear factor Y(NF-Y)transcription factors and plant hormones play important roles in multiple plant growth developmental processes.According to reports,there is much evidence that NF-Y cooperates with phytohormones to regulate plant growth and development modules,but it is unclear whether NF-Y is involved in the JA signaling pathway to affect antiviral responses.In this study,we rely on the artificial virus reception system to explore the role of Os NF-YA in rice viruses.We used genetic analyses to confirm that Os NF-YAs negatively regulate rice resistance,and then used molecular biological and transcriptomics analyses to reveal the molecular mechanism of Os NF-YAs negatively impact defense against viruses by inhibiting the JA-mediated antiviral defense.The results were listed as follows:1.Firstly,we analyzed the expression changes of NF-YA genes in viruses infected rice plants q RT-PCR,and the results showed that a number of Os NF-YA family genes were significantly up-regulated after inoculation with two different viruses.To further explore the role of Os NF-YAs in defense against viruses,RNA interference technology was used to silence Os NF-YAs and generated stable RNAi-Os NF-YA mutants,at the same time,the stable Os NF-YA(Os NF-YA1,Os NF-YA2,Os NF-YA10)overexpressing plants were also generated.Viral inoculation assays demonstrated that the overexpression of Os NF-YAs transgenic plants exhibited increased susceptibility to both RSV and SRBSDV infection,and the accumulation of viral in those transgenic plants were increased compared with the control.However,the RNAi-Os NF-YA transgenic plants showed more resistance to RSV or SRBSDV infection,and the accumulation of viral were reduced compared with the control.These results indicated that Os NF-YAs positively regulate the infection of RSV and SRBSVD.2.To further reveal the mechanism of Os NF-YAs negatively regulating antiviral infection in rice,we analyzed the gene expression of RSV-infected plants by a genomewide transcriptomic analysis.We found that a large number of genes related to JA signal transduction pathway and metabolic pathway were down-regulated in the Os NF-YA2 overexpression plants under RSV infection conditions compared with the control.We further determined the expression levels of the JA-related genes by q RT-PCR and found the results were consistent with transcriptome sequencing in Os NF-YA2 transgenic lines infected by RSV or SRBSDV.These results suggest that Os NF-YAs may be involved in the susceptibility of rice to viruses through the JA pathway.Exogenous hormone treatment experiment showed that JA treatment significantly enhanced the resistance of wild-type rice plants to RSV infection and the accumulation of viral was significantly reduced.However,the degree of disease and the accumulation of viral no significant changes in the Os NF-YA2 overexpressing plants.3.In our previous study,JA signaling key transcription factors Os MYC2/3 play vital roles in antiviral immunity against both RSV and SRBSDV.The results of this study showed that Os NF-YAs inhibited JA signaling pathway.Thus,we hypothesized that Os NF-YAs might physically associate with Os MYC2/3.To further confirm We used to found the interaction between Os NF-YAs and Os MYC2/3,an important transcription factor of JA pathway.To further confirm our hypothesis,the interaction between Os NF-YAs and Os MYC2/3 in vivo and vitro was verified by yeast two-hybrid,co-immunoprecipitation,luciferase complementation imaging and bimolecular fluorescence complementation assay.Based on the conserved sequence characteristics,we found TAD domain was required for the interaction between Os NF-YAs and Os MYC2/3.According to reports,the transcription factors MYC usually have a putative transcriptional activation domain(TAD).In the JA signaling pathway,MED25 is a subunit of the mediating complex,and constitutes the transcription-activating complex with MYC2/MYC3 by binding to the TAD domain.A dual luciferase assay showed that the transcriptional activation activity of Os MYC2/3 was significantly impaired in the presence of Os NF-YA1/ Os NF-YA2.To further confirm our speculation,the association between Os MED25 and Os MYC2/3 was significantly reduced in the presence of Os NF-YAs in vivo and vitro was verified by Co-immunoprecipitation(COIP),Luciferase complementation imaging(LCI)and Bimolecular fluorescence complementation(Bi FC)assay.In summary,our results revealed a mechanism of NF-YA transcription factor suppress jasmonic acid pathway-mediated facilitate viral infection in rice.Os NF-YAs were shown to physically interact with Os MYC2/3,directly disturbing the Os MYC2/3-Os MED25 complex by competing for the TAD domain.Together,our results showed that Os NF-YAs inhibit JA signaling by directly interacting with and impeding the transcriptional activity of Os MYC2/3 to promote viral infection in rice.