Fourteen compounds, including three new isochromenes (1-3) and four new isoquinolines (4-7), were isolated from Streptomyces mirabilis YMZU50. The anti-tobacco mosaic virus (TMV) activities of compounds 1-8 and 13 were evaluated. Compound 6 exhibited the strongest inactivation and protective effects, with inhibition rates of 76.8 and 80.2%, respectively, surpassing the positive control ningnanmycin (45.8 and 43.6%). It also demonstrated curative effects in mildly (grades 1-3) and severely (grade 9) infected plants, reducing severity to grades 1 and 3, respectively. Transmission electron microscopy (TEM) observations confirmed a direct viral particle disruption. Physiological and biochemical analyses revealed a significant enhancement of defense-related enzymes and salicylic acid (SA)accumulation in tobacco. Transcriptomic profiling indicated strong upregulation of photosynthesis-related genes, while metabolomic analysis revealed changes in defense-associated metabolites. These results demonstrate compound 6 as a promising eco-friendly antiviral agent with multimodal TMV control mechanisms, underscoring the potential of Streptomyces-derived products for sustainable crop protection.
Yang et al. (Sun,) studied this question.