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.

Plant viruses are a group of intracellular pathogens that persistently threaten global food security. Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years, including basic research and technologies for preventing and controlling plant viral diseases. Here, we review these milestones and advances, including the identification of new crop‐infecting viruses, dissection of pathogenic mechanisms of multiple viruses, examination of multilayered interactions among viruses, their host plants, and virus‐transmitting arthropod vectors, and in‐depth interrogation of plant‐encoded resistance and susceptibility determinants. Notably, various plant virus‐based vectors have also been successfully developed for gene function studies and target gene expression in plants. We also recommend future plant virology studies in China.

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.