Abstract
Plants are often simultaneously exposed to diverse environmental stresses, and can tune suitable responses to them through hormones. Salicylic acid (SA) and jasmonic acid (JA) signaling pathways are known to enhance resistance against heat stress and tomato yellow leaf curl Thailand virus (TYLCTHV) infection. However, there is limited information regarding alternative natural priming agents against heat stress and viruses. In this study, two plant-derived priming agents, eugenol and anise oil, were tested for their roles in conferring thermotolerance and virus resistance in tomato plants. Under heat stress, the survival rates and average fresh weight were higher in plants treated with eugenol or anise oil than in control plants. These two priming agents were further tested for antiviral activities. After TYLCTHV infection, the disease incidence and relative abundance of TYLCTHV were lower in anise oil- and eugenol-treated plants than in control plants. Further analyses revealed that a few SA, JA, and RNA silencing genes were enhanced in the former. Moreover, SA, JA, and H2O2 contents increased considerably after eugenol and anise oil treatments. Our findings imply that anise oil and eugenol initiated SA- and JA-mediated defenses to promote thermotolerance and antiviral responses of tomato plants.
Highlights
Plants are often exposed to multiple biotic and abiotic stresses throughout their lifespan
To assess the effects of eugenol and anise oil on tomato seedlings under heat stress conditions, 12day-old tomato seedlings were sprayed with control solution, eugenol (200 μg mL−1), or anise oil (200 μg mL−1) three times daily
Plants treated with eugenol or anise oil grew well after the heat treatment and 5-day recovery period, those treated with anise oil (Figure 1B)
Summary
Plants are often exposed to multiple biotic and abiotic stresses throughout their lifespan Their survival requires sophisticated sensory systems that perceive various stress signals and activate the most appropriate responses at the molecular, cellular, and physiological levels. Certain stresses that occur sequentially or simultaneously can enhance plant tolerance to other abiotic or biotic stresses (Foyer et al, 2016; Hossain et al, 2018). The naturally occurring metabolic stimuli include vitamins, hormones, amino acids, growth-promoting molecules, and reactive oxygen-nitrogensulfur species that initiate complex signal transduction pathways and alter gene expression to enhance plant tolerance to abiotic and biotic stresses (Athar et al, 2008; Arnao and HernandezRuiz, 2014; Christou et al, 2014; Li T. et al, 2014; Savvides et al, 2016). In addition to naturally occurring stimuli, benzothiadiazole and kresoxim-methyl have been synthesized and applied to induce plant defenses (Filippou et al, 2016)
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