Validamycin A Induced Resistance in Rice against Rhizoctonia solani via the Salicylic Acid-Depended Signaling Pathway

Validamycin A (VMA), the major active component of validamycin, provides effective control of rice sheath blight; however, the mechanisms underlying VMA-induced resistance to Rhizoctonia solani remain poorly understood. Here, we integrated antioxidant enzyme assays, phytohormone profiling, transcriptomics, and metabolomics to investigate VMA-induced immunity in rice. VMA improved oxidative stress tolerance by enhancing antioxidant enzyme activities and activating glutathione metabolism. Moreover, VMA established a primed multihormonal state characterized by elevated salicylic acid (SA), jasmonic acid (JA) levels, while disease resistance was specifically governed by the SA signaling pathway. Functional analyses of SA-deficient mutants (pal1, pal2, and pr1a) indicated that VMA-mediated immunity is primarily dependent on SA-associated defense. BR appeared to contribute to response tuning, and JA-associated changes suggested possible hormone crosstalk. These findings clarify the mechanism of VMA-induced resistance and expand understanding of chemical elicitor-mediated immunity against necrotrophic pathogens in rice.