Genetic basis of phytoalexin-mediated chemical defense in plants
Zhanli Wang1, Lu Han1, Lei Gao2
1State Key Laboratory of Membrane Biology, MOE Key Laboratory of Bioinformatics, Center for Plant Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China; Tsinghua-Peking Center for Life Sciences, Beijing 100084, China.
Abstract:
Phytoalexins are core components of plant chemical defense against pathogens. However, the genetic basis and regulatory mechanisms governing their biosynthesis remain preliminary. Debneyol is a well-defined, broad-spectrum fungicidal phytoalexin. Here, we elucidate its biosynthetic pathway, key regulators, and activity against multiple pathogens. We show that debneyol is synthesized from farnesyl pyrophosphate (FPP) through three steps catalyzed by 5-epi-aristolochene synthase (EAS), 5-epi-aristolochene epoxidase (EAE), and epoxide hydrolase-1 (EH1). MCD1 (miR1919-targeted cell death-factor-1) interacts with EAS and EAE, enhancing their association and EAE activity and promoting debneyol biosynthesis. Increased MCD1 expression confers plant resistance not only against fungal but also viral and bacterial pathogens. Our work reveals a complete plant phytoalexin-based chemical defense machinery, opening avenues for engineering broad-spectrum plant resistance and industrial-scale debneyol production via synthetic biology.
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