Summary: Plant hormones play a vital role in plant immune responses. However, in contrast to the relative wealth of information on hormone‐mediated immunity in dicot plants, little information is available on monocot–virus defense systems. We used a high‐throughput‐sequencing approach to compare the global gene expression of Rice black‐streaked dwarf virus (RBSDV)‐infected rice plants with that of healthy plants. Exogenous hormone applications and transgenic rice were used to test RBSDV infectivity and pathogenicity. Our results revealed that the jasmonic acid (JA) pathway was induced while the brassinosteroid (BR) pathway was suppressed in infected plants. Foliar application of methyl jasmonate (MeJA) or brassinazole (BRZ) resulted in a significant reduction in RBSDV incidence, while epibrassinolide (BL) treatment increased RBSDV infection. Infection studies using coi1‐13 and Go mutants demonstrated JA‐mediated resistance and BR‐mediated susceptibility to RBSDV infection. A mixture of MeJA and BL treatment resulted in a significant reduction in RBSDV infection compared with a single BL treatment. MeJA application efficiently suppressed the expression of BR pathway genes, and this inhibition depended on the JA coreceptor OsCOI1. Collectively, our results reveal that JA‐mediated defense can suppress the BR‐mediated susceptibility to RBSDV infection.

Optimizing cytokinin distribution patterns is a promising strategy for simultaneously enhancing grain yield, grain quality, and stress resistance in plants, as

OsGSK2 directly interacts with and destabilizes OsJAZ4 to activate JA-mediated defense signaling.

Significance: Auxin signaling plays essential roles in almost every aspect of plant growth and development. Auxin response factors (ARFs) are key transcriptional regulators of auxin signaling. However, it is not clear what roles ARF transcription factors may play in plant–pathogen, and specifically plant–virus, interactions. This study reveals that an ARF transcription factor is targeted by several independently evolved viral proteins of very different plant RNA viruses. These viral proteins impede the ARF activity in different ways, but in each case, these interactions benefit viral infection. These findings demonstrate that manipulation of the auxin signaling by viral proteins is a common pathogenicity strategy in plant RNA viruses.