A Novel Thiazolidin-2-Cyanamide Derivative Suppresses Bacterial Blight by Targeting the Type III Secretion System and Reassembling a Protective Rice Leaf Microbiome

Xanthomonas oryzae pv. oryzae (Xoo), the causal agent of rice bacterial leaf blight, relies on a type III secretion system (T3SS) for virulence. Using chemical inhibitors to suppress T3SS without affecting bacterial growth is a novel strategy that minimizes disturbance of the innate leaf microbiome. (Z)-N-(3-(5-(2-nitrophenyl) furan-2-carbonyl) thiazolidin-2-ylidene) cyanamide (II-2) is a chemical inhibitor of T3SS in Xoo and an effective control alternative. This study evaluated whether II-2 treatment and Xoo infection alter the leaf microbiome. Using 16S rRNA gene sequencing, Xoo infection markedly reshaped the leaf microbiome, shifting the dominance from Proteobacteria to Pseudomonadales and Xanthomonadales. II-2 influenced bacterial communities in both healthy and Xoo-infected leaves, with low-dose treatment enriching Gram-negative taxa in diseased leaves, whereas the high dose enriched Sphingomonas in healthy leaves. In healthy plants, higher II-2 doses preserved microbial stability, suggesting minimal ecological disturbance. II-2 exhibited no toxicity in silkworms or earthworms, functioning as a T3SS-targeting, microbiome-compatible antivirulence agent.