Mechanisms of Tetramycin-Induced Resistance to Rice Blast Disease in Oryza sativa L.

Rice blast, caused by the fungus Magnaporthe oryzae, is a devastating disease that threatens global food security, causing annual yield losses of 10–30%. Consequently, novel control strategies beyond conventional fungicides are urgently needed. Tetramycin, a polyene macrolide antibiotic, is known for its broad-spectrum antifungal activity. However, the specific mechanisms underlying its efficacy against rice blast remain to be fully elucidated. In this study, we demonstrate that tetramycin confers resistance through a dual mode of action. First, in vitro assays revealed that tetramycin directly inhibits M. oryzae mycelial growth. Second, and more critically, it functions as a potent immune elicitor in Oryza sativa. Transcriptome analysis coupled with physiological assays showed that tetramycin treatment triggers a rapid oxidative burst, characterized by significantly elevated activities of key defense enzymes, including superoxide dismutase, peroxidase, phenylalanine ammonia lyase, and polyphenol oxidase (PPO). This oxidative response is further orchestrated through the simultaneous activation of the jasmonic acid (JA) and salicylic acid (SA) signaling pathways, as evidenced by the distinct upregulation of their respective biosynthetic genes and hormone levels. Collectively, these findings indicate that tetramycin not only acts as a direct fungicide but also primes the rice innate immune system via a synergistic reactive oxygen species-JA-SA signaling network, offering a sustainable strategy for rice blast management.