# Ubiquitin-Conjugating Enzyme Positively Regulates Salicylic Acid and Jasmonic Acid Biosynthesis to Confer Broad-Spectrum Antiviral Resistance in Nicotiana benthamiana

## TL;DR

A ubiquitin-conjugating enzyme helps plants resist viruses by boosting the production of key hormones.

## Contribution

This study reveals a new role for UBC in regulating antiviral defense through salicylic and jasmonic acid biosynthesis.

## Key findings

- UBC-silenced plants showed increased susceptibility to TuMV infection.
- UBC overexpression suppressed viral propagation in plants.
- Exogenous SA or JA partially restored resistance in UBC-silenced plants.

## Abstract

Ubiquitin-conjugating enzyme (UBC) plays a significant role in plant hormone signal transduction. In this study, we observed that TuMV infection markedly upregulates UBC mRNA expression, suggesting a close association between UBC and viral infection. Using Tobacco rattle virus (TRV)-based virus-induced gene silencing (VIGS) to downregulate UBC expression in Nicotiana benthamiana, we found that UBC-silenced plants exhibited enhanced susceptibility to TuMV compared with control plants. Conversely, transient overexpression of UBC protein suppressed viral propagation. Further analysis by reverse transcription quantitative PCR (RT-qPCR) revealed a substantial downregulation in the expression of SA and JA biosynthetic genes in UBC-silenced plants. Accordingly, liquid chromatography–tandem mass spectrometry (LC-MS/MS) confirmed a marked decrease in the accumulation of the corresponding hormones. Exogenous application of SA or JA partially restored antiviral resistance in UBC-silenced plants, indicating that hormonal deficiency contributes to enhanced viral susceptibility. Collectively, our results demonstrate that UBC positively regulates SA and JA biosynthesis. UBC silencing impairs both SA- and JA-mediated defense pathways, thereby facilitating viral infection in N. benthamiana.