Inhibitory activity and antifungal mechanism of venturicidin A against Pyricularia oryzae

Rice blast, caused by Pyricularia oryzae, is a devastating disease threatening global rice production. Microbial secondary metabolites represent promising alternatives for disease control. Venturicidin A (VentA), isolated from Streptomyces sp. SN5452, has been shown to inhibit the growth of fungal species, but its antifungal activity and mechanism against P. oryzae remain unclear. Here, 135 strains of P. oryzae were isolated from rice-growing areas in Liaoning Province to establish a baseline sensitivity of P. oryzae to VentA, with a unimodal distribution of EC₅₀ values ranging from 0.072 to 0.611 μg/mL and a mean value of 0.185 ± 0.103 μg/mL. VentA significantly suppressed conidiation and appressoria formation, altered hyphal morphology, and impaired cell integrity. At 100 μg/mL, VentA exhibited protective (60.74 %) and curative (55.68 %) efficacy against rice blast. Transcriptomic analysis identified 3449 differentially expressed genes (DEGs), among which those involved in the mitogen-activated protein kinase (MAPK) signaling pathways and cellular energy metabolism were significantly downregulated, while DEGs related to ribosome and aminoacyl-tRNA biosynthesis were upregulated. Biochemical assays confirmed that VentA inhibited ATP synthesis. VentA may inhibit P. oryzae by suppressing MAPK-mediated host penetration and disrupting cellular energy metabolism, highlighting its potential as an alternative fungicide for rice blast control. This study provides new evidence on the inhibitory mechanisms of VentA against P. oryzae.