Abstract
Plant viruses can cause substantial yield losses, yet disease severity often varies between seasons because plants frequently experience heat or cold episodes before infection. In this study, we tested whether such temperature conditions affect the plant’s redox balance and alter its response to Tomato bushy stunt virus (TBSV) infection in Nicotiana benthamiana. Plants were exposed to short-term heat and cold stress, after which they recovered before virus inoculation. Following this, we assessed the reactive oxygen species (ROS) content, lipid peroxidation (LPO), oxidative DNA damage, stress-related proteins, redox-associated enzymes, and antioxidant metabolites. TBSV led to non-parallel ROS responses during infection, with consistently elevated hydrogen peroxide in infected plants but reduced superoxide relative to corresponding mock controls. Heat pre-exposure caused pronounced LPO that decreased further after infection, whereas cold pre-exposure stabilized malondialdehyde near levels observed at 25 °C. Both thermal stress and infection increased 8-oxo-dG and were associated with distinct changes in 8-oxoguanine glycosylase abundance. Infection strongly induced heat shock protein 90 (and moderately heat shock protein 70), while prior heat limited further chaperone induction by TBSV. These results indicate that viral infection develops within and is limited by the host’s oxidative state, where redox homeostasis may restrict infection-related processes, and infection leads to changes in this redox environment that are favorable for its development.