Exogenous Quercetin Treatment Provides Insights Into Transcriptional Regulatory Network for Salt Tolerance of <scp><i>Triticum urartu</i></scp>

Quercetin, a well-known antioxidant, plays a crucial role in the response of plants to biotic and abiotic stresses. Triticum urartu is the donor of the A subgenome of common wheat. This study aimed to reveal the mechanism by which quercetin treatment alleviates salt stress in T. urartu. The quercetin treatment resulted in the reduction of Na⁺ content and enhancement of K⁺ content in the stressed leaves, while it elevated the Na⁺ content in the stressed roots. This indicated that under salt stress, quercetin treatment can promote transporting K⁺ to the leaves and retaining Na⁺ in the roots. Transcriptome analysis showed that in the roots, quercetin treatment increased the expression level of several genes encoding the rate-limiting enzyme for ethylene biosynthesis, core ethylene signaling proteins, and negative regulators of the core ABA signaling pathway (abscisic acid 8'-hydroxylase and protein phosphatase 2C) under salt stress, revealing that quercetin treatment may induce ethylene signal and suppress ABA signal. We observed that quercetin treatment increased the expression level of several respiration genes in roots under salt stress, including 36 glycolysis genes, 18 mitochondria-related genes, and 4 ATP synthase genes. This displayed that quercetin treatment may enhance the respiration of T. urartu. The enhancement of respiration will provide more energy and carbon sources for salt stress response. Overall, quercetin treatment alleviates the negative effect of salt stress in T. urartu plants via multiple mechanisms, offering potential for improving plant salt tolerance.