Genome Mining Leads to Rare Calbistrin Derivatives with Potent Herbicidal Activity from the Endophytic Fungus <i>Aspergillus japonicus</i> TE-739D

Genomic mining identified a distinct <i>cal</i>″ biosynthetic gene cluster from the endophytic fungus <i>Aspergillus japonicus</i> TE-739D, thereby leading to the discovery of nine novel calbistrin derivatives, namely, japonidienes A-I (<b>1</b>-<b>9</b>), along with three known analogs (<b>10</b>-<b>12</b>). Their structures were elucidated by spectroscopic data analysis and quantum chemical calculations. Notably, compound <b>1</b> possessed a unique scaffold, in which the polyene moiety generated a cyclopentanone motif. Based on bioinformatic analyses and homology comparisons with reported calbistrin pathways, a hypothetical biosynthetic route for these isolated calbistrin-type compounds was proposed, which demonstrated an elegant example of modular polyketide assembly and diversified postmodifications. Compound <b>6</b> demonstrated potent herbicidal efficacy in suppressing <i>Eleusine indica</i> when compared with the positive control glyphosate. Further mechanistic investigations employing transcriptomic and proteomic analyses revealed that compound <b>6</b> disrupted MAPK signaling and influenced ABA-mediated seed dormancy pathways. This study is the first to report the herbicidal activity of rare calbistrin-type compounds, highlighting their potential as candidates for natural herbicide development.