NbNAC42 and NbZFP3 Transcription Factors Regulate the Virus Inducible Promoter in .

Plant argonautes (AGOs) play important roles in the defense responses against viruses. The expression of gene () is highly induced by (BaMV) infection; however, the underlying mechanisms remain elusive. In this study, we have analyzed the potential promoter activities of and its interactions with viral proteins by using a 2,000 bp fragment, designated as PN1, upstream to the translation initiation of PN1 and seven serial 5'-deletion mutants (PN2-PN8) were fused with a β-glucuronidase (GUS) reporter and introduced into the genome by -mediated transformation for further characterization. It was found that PN4-GUS transgenic plants were able to drive strong GUS expression in the whole plant. In the virus infection tests, the GUS activity was strongly induced in PN4-GUS transgenic plants after being challenged with potexviruses. Infiltration of the transgenic plants individually with BaMV coat protein (CP) or triple gene block protein 1 (TGBp1) revealed that only TGBp1 was crucial for inducing the promoter. To identify the factors responsible for controlling the activity of the promoter, we employed yeast one-hybrid screening on a transcription factor cDNA library. The result showed that NbNAC42 and NbZFP3 could directly bind the 704 bp promoter regions of . By using overexpressing and virus-induced gene silencing techniques, we found that NbNAC42 and NbZFP3 regulated and downregulated, respectively, the expression of the gene. Upon virus infection, NbNAC42 played an important role in regulating the expression of NbAGO5. Together, these results provide new insights into the modulation of the defense mechanism of against viruses. This virus inducible promoter could be an ideal candidate to drive the target gene expression that could improve the anti-virus abilities of crops in the future.