Transcriptional Regulation of Pokeweed Antiviral Protein

Phytolacca americana (American pokeweed) expresses pokeweed antiviral protein (PAP), a ribosome-inactivating protein (RIP) thought to function in defence. Several PAP isoforms are differentially responsive to jasmonic acid (JA), a phytohormone that mediates resistance against pathogen infections and herbivory. However, few RIP promoters have been characterized and little is known about RIP regulation in their native contexts. In this study, I identified the PAP promoters and discovered long introns in the 5 untranslated regions (5UTRs) of PAP genes. qRT-PCR and reporter assays revealed that both the PAP-I promoter and intron can independently drive gene expression, leading to the transcription of mRNA variants with distinct 5UTRs. In addition, a G-BOX promoter element was found to be required for the JA-mediated upregulation of PAP-I. Differential expression analysis confirmed that several PAP isoforms are responsive to other stresses, in addition to JA. This foundational work sheds light on the endogenous regulation of PAP.