Suppression of defense gene expression under nutrient-rich condition in <i>Arabidopsis</i> seedlings

Plant hormones like salicylic acid (SA) and jasmonic acid (JA) play crucial roles in regulating defense gene expression systems. SA mainly regulates defense against biotrophic pathogens, while JA mediates defense against necrotrophic pathogens. Compounds called plant activators including probenazole, acibenzolar-s-methyl and 2,6-dichloroisonicotinic acid (INA) activate plant immune systems, providing protection against pathogens. Unlike conventional pesticides that directly target pathogens, plant activators boost the host's defense mechanisms, potentially reducing the likelihood of drug resistance development. Various high-throughput screening systems (HTS) have been developed with the aim of searching for plant activators. Transgenic <i>Arabidopsis</i> lines expressing luciferase under the control of defense gene promoters allow us to monitor the activity of defense-related gene in vivo. To investigate the influence of nutrients on the HTS system, we conducted luciferase assays using <i>Arabidopsis</i> seedlings and observed the suppression of defense gene expression in response to the treatment of plant activators. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was employed to monitor the expression levels of endogenous genes in response to nutrient-rich conditions and confirmed the suppression effect of defense gene expression as observed in the luciferase reporter assays. The findings highlight the importance of considering nutrient effects when evaluating plant activators and screening for compounds that induce defense gene expression under nutrient-rich conditions.