Physiological, biochemical, and transcriptomic analyses unveil the mechanisms of melatonin in improving wheat stripe...

Melatonin has been well known to be involved in biotic and abiotic stress; however, the potential mechanisms and function in wheat stripe rust remain unclear. In this study, wheat cultivar SY95-71 was used to investigate the protective roles in wheat against stripe rust (the Chinese Pst race CY32) by foliar applied melatonin with different concentrations. The results showed that stripe rust infection for 120 h significantly reduced photosynthetic efficiency and antioxidative capacity, and caused severe cell damage in wheat. Exogenous melatonin treatment significantly alleviated cell death and callose deposition, while greatly increased photosynthetic capacity and enzymatic activities at 120 hpi. Furthermore, melatonin application alleviated the decrease in PsbA content and increased the levels of PsbS and Lhcb5. In addition, 200 differentially expressed genes were identified between the nonmelatonin/infected wheat and melatonin/infected wheat. Further detailed analysis documented that melatonin could improve stripe rust resistance by enhancing five genes associated with amino acid metabolism and protein processing. Moreover, melatonin manipulated the expression of phenylpropanoid metabolism-related genes to improve wheat resistance through changing the expression levels of MYB transcription factors. Therefore, the research provides new insights into the protective role and mechanisms of melatonin in wheat against stripe rust infection, particularly through the genes related to disease resistance and metabolic pathways.