Genome Assembly of Dactylobotrys graminicola Reveals the Terpene Toxin Biosynthesis Gene Cluster that Uncovers 4,15-Diacetylverrucarol as a Phytotoxin with Virulence and Herbicidal Activity

Dactylobotrys graminicola (Dgr) is a new pathogen causing barley sheath rot, whose incidence has considerably increased in recent years, leading to severe yield losses and crop quality decline, particularly in the Tibetan Plateau region. However, the pathogenic mechanisms of Dgr and the strategies to control this disease are largely unexplored. Herein, we report a 31.6 Mb draft genome sequence of Dgr that encodes 9,594 predicted genes. Evolutionarily, Dgr is close to Fusarium spp., suggesting that it may have the potential to produce trichothecene, similar to Fusarium spp. Further bioinformatic analysis identified a trichothecene biosynthetic gene cluster in Dgr with the genes exhibiting high expression levels during the early stages of infection. We screened and determined the specific conditions that enable Dgr to produce toxins and successfully isolated and identified the toxin as 4,15-diacetylverrucarol (Dao). Virulence assays demonstrated that Dao was able to disrupt plant cell structures and facilitate the infection of Dgr. Subsequent studies revealed that monocotyledonous plants exhibited greater susceptibility to Dao compared to dicotyledonous plants, indicating Dao's potential as a selective herbicide. Overall, our study uncovers the genome sequence of Dgr and demonstrate that the toxin of Dao acts as a virulence factor and may serve as a potential selective herbicide. These findings offer new insights into the pathogenic mechanisms of Dgr and highlight the potential of Dao for weed control.