Underground microbial ecosystems have profound impacts on plant health^1,2,3,4,5. Recently, essential roles have been shown for plant specialized metabolites in shaping the rhizosphere microbiome^6,7,8,9. However, the potential mechanisms underlying the root-to-soil delivery of these metabolites remain to be elucidated¹⁰. Cucurbitacins, the characteristic bitter triterpenoids in cucurbit plants (such as melon and watermelon), are synthesized by operon-like gene clusters¹¹. Here we report two Multidrug and Toxic Compound Extrusion (MATE) proteins involved in the transport of their respective cucurbitacins, a process co-regulated with cucurbitacin biosynthesis. We further show that the transport of cucurbitacin B from the roots of melon into the soil modulates the rhizosphere microbiome by selectively enriching for two bacterial genera, Enterobacter and Bacillus, and we demonstrate that this, in turn, leads to robust resistance against the soil-borne wilt fungal pathogen, Fusarium oxysporum. Our study offers insights into how transporters for specialized metabolites manipulate the rhizosphere microbiota and thereby affect crop fitness.

地下微生物生态系统对植物健康具有深远影响^1,2,3,4,5。最近，植物特化代谢物在塑造根际微生物群中的重要作用已被证明^6,7,8,9。然而，这些代谢物从根部传递到土壤的潜在机制仍有待阐明¹⁰。葫芦素是葫芦科植物（如甜瓜和西瓜）中特有的苦味三萜类化合物，由类操纵子基因簇合成¹¹。在这里，我们报告了两种多药和有毒化合物挤出（MATE）蛋白参与各自葫芦素的转运，这是一个与葫芦素生物合成共同调节的过程。我们进一步表明，葫芦素 B 从甜瓜根部转运到土壤中，通过选择性富集肠杆菌属和芽孢杆菌属这两个​​细菌属来调节根际微生物组，并且我们证明这反过来又会导致对土壤的强大抵抗力。枯萎病真菌病原体，尖镰孢。我们的研究提供了关于特殊代谢物的转运蛋白如何操纵根际微生物群从而影响作物适应性的见解。