Dark septate endophytes (DSEs) are the typical representatives of root endophytic fungi in heavy metal (HM)-contaminated environments. However, little is known about their roles in the HMs tolerance of hosts and the underlying mechanism. Here, we investigated the biological roles and molecular mechanisms of a DSE strain Falciphora oryzae in alleviating cadmium (Cd) toxicities in rice. It was found that F. oryzae possessed a capacity of accumulating Cd in its vacuoles and chlamydospores. During symbiosis, F. oryzae conferred improved Cd tolerance to rice, decreasing Cd accumulation in roots and translocation to shoots. F. oryzae alleviated Cd toxicity to rice by sequestering Cd in its vacuoles. Further application of F. oryzae as fertilizer in the field could reduce Cd content in rice grains. We identified a SNARE Syntaxin 1 gene through proteomics, which participated in Cd tolerance of F. oryzae by regulating chlamydospore formation and vacuole enlargement. This study provided novel insights into how the DSEs and their host plants combat Cd stress.

深色有隔内生菌 (DSE) 是重金属 (HM) 污染环境中根内生真菌的典型代表。然而，关于它们在宿主的 HMs 耐受性中的作用和潜在机制知之甚少。在这里，我们研究了 DSE 菌株Falciphora oryzae在减轻水稻中镉 (Cd) 毒性方面的生物学作用和分子机制。研究发现，F. oryzae具有在其液泡和厚壁孢子中积累 Cd 的能力。在共生过程中，F. oryzae提高了水稻对镉的耐受性，减少了根中镉的积累和向芽的易位。F. oryzae通过在其液泡中隔离 Cd 来减轻 Cd 对水稻的毒性。进一步应用F. oryzae作为田间肥料可以降低稻谷中Cd的含量。我们通过蛋白质组学鉴定了一个 SNARE Syntaxin 1 基因，该基因通过调节厚壁孢子形成和液泡增大参与了稻瘟病菌的Cd 耐受性。这项研究为 DSE 及其寄主植物如何对抗 Cd 胁迫提供了新的见解。