Yaling Zhao

Southem rice black-streaked dwarf virus (SRBSDV), a fijivirus with a double-stranded RNA genome of 10 segments and 13 proteins, severely impairs rice growth and development. The functions of P8, one of the major coat proteins of SRBSDV, are still poorly understood. In this study, the SRBSDV-encoded P8 protein was used as bait in a yeast two-hybrid screen of a rice cDNA library, which identified an interaction between P8 and auxin response factor 15 (OsARF15). The interaction was then confirmed by GST pull-down (in vitro) and co-immunoprecipitation (Co-IP) (in vivo) assays. Truncated protein analysis further revealed that P8 primarily binds to the C-terminal region of OsARF15. Over-expression and knockout of OsARF15 rice plants were constructed and then inoculated by SRBSDV. The results showed that over-expression of OsARF15 promoted SRBSDV infection whereas its knockout enhanced virus resistance. Meanwhile, the effect of OsARF15 on root development was observed and found that knocking out OsARF15 significantly promoted the growth of rice roots at the seeding stage. These results demonstrate that the SRBSDV P8 protein facilitates viral infection by interacting with the C-terminal region of OsARF15. Our findings have further strengthened the role of P8 in the viral infection process.

Cucumber mosaic virus (CMV), a representative species of the genus Cucumvirus in the family Bromoviridae, is globally distributed and infects over 1200 monocot and dicot plants. 14-3-3 proteins serve as molecular adaptors that bind phosphorylated target proteins and play significant roles in multiple signaling pathways, including plant growth and development, hormone signaling, and responses to abiotic and biotic stimuli. Although an increasing body of evidence supports the prominent roles of 14-3-3 proteins in regulating plant immunity, their specific roles in plant responses to CMV infection remain unclear. Here, we demonstrate that 14-3-3λ and 14-3-3κ knockout Arabidopsis plants display enhanced tolerance to CMV infection, with significantly suppressed viral replication compared to wild-type (WT) plants. Additionally, we conducted transcriptomics analysis by comparing the CMV-infected 14-3-3λ 14-3-3κ (14-3-3λ/κ) double mutant to the WT using RNA-seq. The KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment and differentially expressed gene (DEG) results mainly suggest that plant hormone signaling, transcription factor activity, and the autophagy pathway are significantly involved in 14-3-3-mediated CMV tolerance in Arabidopsis. This study reveals new functions and potential molecular mechanisms of 14-3-3 proteins in regulating plant response to CMV infection and provides valuable insights into agricultural production.