The Pathogenesis-Related Protein 4b Induced by Rice Stripe Virus Enhances Host's Antiviral Defence

Rice stripe virus (RSV) causes rice stripe disease, which poses a serious threat to rice production. Pathogenesis-related (PR) proteins are well known for their ability to enhance plant resistance against pathogen infection; however, reports on the involvement of PR proteins in antiviral defence remain limited. In this study, we found that the expression of PR4b was significantly upregulated in RSV-infected plants. To investigate the functional relationship between RSV infection and PR4b expression, we generated rice lines differentially expressing OsPR4b. Phenotypic and molecular analyses showed that, compared with wild-type plants, OsPR4b-overexpressing plants exhibited enhanced resistance to RSV, characterized by milder viral symptoms and reduced viral accumulation. In contrast, knockdown of OsPR4b compromised the host's resistance to RSV, resulting in more severe symptoms and increased viral accumulation. Transcriptomic analysis indicated that knockdown of OsPR4b activated pathways related to RNA metabolism, oxidative stress, phenylpropanoid biosynthesis and glyoxylate metabolism. These results imply that OsPR4b may confer antiviral resistance through multiple mechanisms: regulating RNA metabolism to indirectly modulate viral replication complex activity, and influencing cell wall construction and metabolic homeostasis to indirectly affect intercellular viral movement and replication. Collectively, these findings identify PR4b as a novel target for plant antiviral breeding.