The reactivation of detoxification enzymes by red light at night contributes to a more successful defence against Fusarium graminearum in wheat ears

Nocturnal red light application affects defence-related enzymes in wheat, in particular antioxidants and glutathione transferases (GSTs), which are crucial for successful plant defence. In our study, we sought to answer the question of whether night-time illumination during anthesis induces detectable changes in the infection responses of wheat cultivars with different levels of Fusarium resistance . To address this question, we investigated a range of factors from yield parameters and membrane status to changes in enzyme activities and gene expression and its regulation. Nocturnal red light treatment increased the activities of superoxide dismutase, catalase, guaiacol-dependent peroxidase and GSTs. In parallel with increased activity of detoxification enzymes, a higher grain yield was observed in the more resistant wheat line during infection by Fusarium graminearum . Notably, GSTs , which are typically down-regulated in darkness, were strongly up-regulated by red light at night in the more susceptible cultivar, especially TaGSTU1B and TaGSTF5 . In addition, an exceptionally high and light-dependent transcriptional activity of TaGSTF5 was detected in the sensitive line. Sequence analysis of the regulatory region of TaGSTF5 identified an additional GATA box, a circadian regulatory element, which may be responsible for the increased transcript levels. These results suggest that nocturnal red light can effectively enhance antioxidant and GST activity as part of the defence of wheat against Fusarium head blight, but this depends on the Fusarium resistance of the selected wheat genotypes. • Nocturnal red light induces changes in the defence responses of wheat varieties. • Red light increased the activity of antioxidant enzymes and glutathione transferases. • Fusarium graminearum and light up-regulates TaGSTU1B and TaGSTF5 in the more susceptible cultivar. • GATA box, a circadian regulatory element, can control the transcription of TaGSTF5.