Arbuscular Mycorrhizal Fungus System Recruits Sphingomonas spp. To Resist Drought Resistance In Peanut

Against the background of global climate change, drought stress has emerged as a major factor limiting plant growth and development. The arbuscular mycorrhizal fungus (AMF) Claroideoglomus etunicatum ( C. etunicatum) can increase drought tolerance in peanut ( Arachis hypogaea L.), yet the mechanisms underlying this effect remain largely unclear. Because the assembly of the rhizosphere microbiome plays a critical role in mediating plant stress resistance, we propose that AMF improve peanut drought tolerance by reshaping the rhizosphere microbial community. Here, we investigated the mechanism by which C. etunicatum recruits beneficial bacteria through rhizodeposits, thereby improving host drought tolerance, and elucidated the signal exchange and division of metabolic roles between rhizodeposits and bacterial exudates. Using a soil microcosm system, we demonstrated that C. etunicatum increases peanut drought resistance by selectively enriching Sphingomonas spp. in the rhizosphere, with rhizodeposits likely playing a key role in this recruitment. Furthermore, metabolomic and whole-genome analyses revealed a cross-kingdom signaling cascade in which C. etunicatum induces the synthesis of a primary signaling molecule, L-cysteine, in the rhizodeposits of host plants. L-cysteine further promotes the synthesis of a second signaling molecule, zeatin, in Sphingomonas sp. W9 by regulating the expression of key genes involved in the cysteine and methionine metabolism, sulfur metabolism, terpenoid backbone biosynthesis and zeatin biosynthesis pathways. Coinoculation experiments confirmed that exogenous application of zeatin significantly improved peanut drought tolerance. In summary, we explored the mechanism by which the rhizosphere microbial community affects drought tolerance through cross-kingdom signaling cascade, providing new insights into plant-microbe cooperation under environmental stress.