Arbuscular Mycorrhizal Fungus System Recruits Sphingomonas spp. to Enhance Drought Resistance in Peanut

Against the background of global climate change, drought stress is a major factor limiting plant growth and development. A previous study demonstrated that Claroideoglomus etunicatum (C. etunicatum) could increase drought resistance in peanut (Arachis hypogaea L.), yet the mechanisms underlying this effect remain largely unclear. Here, the mechanisms by which C. etunicatum recruited beneficial bacteria through rhizodeposits to improve host drought resistance were investigated. In a soil microcosm system, C. etunicatum increased peanut drought resistance by enriching Sphingomonas spp. in the rhizosphere, with rhizodeposits likely playing a key role in this recruitment. Furthermore, metabolomic and whole-genome sequencing analyses revealed a cross-kingdom signalling cascade in which C. etunicatum induced the accumulation of the first signalling molecule, L-cysteine, in the rhizodeposits of host plants. The synthesis of a second signalling molecule, zeatin, in Sphingomonas sp. W9 was further promoted by L-cysteine through regulation of key genes in the relevant biosynthetic pathways. Exogenous application experiments confirmed that zeatin significantly improved peanut drought resistance. In summary, this study revealed a mechanism by which the rhizosphere microbial community affected drought resistance through a cross-kingdom signalling cascade, thereby providing new insights into plant-microbe cooperation under environmental stress.