The PSR signaling pathway facilitates enrichment of P-solubilizing Burkholderia to enhance P acquisition in soybean

Abstract

Abstract Background Association with beneficial microbes is essential for plants maintaining fitness under biotic or abiotic stress. Mechanisms underlying this call for community support, and the species involved, remain largely unknown. Results We revealed that the phosphate starvation response (PSR) pathway contributes to enrich the phosphate solubilizing bacteria (PSB) Burkholderia for better P acquisition in soybean. We discovered that P deficiency significantly increased the relative abundance of Burkholderia in soybean roots and rhizospheres in field trials. Constitutively activation of the PSR pathway through overexpression of GmPHR33 significantly enhanced root-associated compartments with Burkholderia , while repression through knockout of GmPHR33 repressed it. Furthermore, the PSR pathway appeared to regulate malate exudation to enrich PSB, while the GmPHR33-GmALMT29 module was revealed as a mediator of the malate exudation process. Conclusions Our results uncovered a novel mechanism utilized by legumes to enrich functional microbes that can help legumes cope with P deficiency. The mechanism elucidated in this work acts through activation of the PSR signaling pathway under P deficiency conditions, which enriches PSB, particularly Burkholderia, for support in acquiring P.