Structure-based targeting of Atg8 uncovers its essential role in autophagy-mediated detoxification.

Abstract

Autophagy degrades and recycles intracellular material, allowing cells to maintain homeostasis and adapt to environmental stress. In the rice blast fungus Magnaporthe oryzae, the core autophagy protein MoAtg8 is required for autophagosome formation and host infection. Here, we determined the crystal structure of MoAtg8 and used it for structure-guided virtual screening of a focused compound library enriched for natural products and autophagy-related molecules. This screen identified nordihydroguaiaretic acid (NDGA), a naturally occurring lignan, as a MoAtg8-binding compound. NDGA suppressed conidial germination and appressorium formation, disrupted membrane integrity, and reduced pathogenicity in M. oryzae, with no detectable phytotoxicity to rice under the conditions tested. Mechanistically, the 5-lipoxygenase Mo5Lox, a target of NDGA, bound NDGA with lower affinity than MoAtg8. MoAtg8 associated with NDGA through Gln81 and promoted its autophagy-dependent delivery to vacuoles, thereby reducing compound availability to toxicity-associated targets. Disruption of autophagy or mutation of Gln81 in MoAtg8 increased fungal sensitivity to NDGA. These findings identify an autophagy-mediated detoxification route for an exogenous antifungal compound and reveal how MoAtg8-dependent trafficking modulates NDGA efficacy in a plant-pathogenic fungus.