Evidence for a Dark Septate Endophyte (Exophiala Pisciphila, H93) Enhancing Phosphorus Absorption by Maize Seedlings

Background and aims Dark septate endophytes (DSE) are a group of multifunctional fungi that ubiquitously colonize the roots of numerous plants worldwide, benefiting the nutrition and adaptation of hosts to various stressed environments. How DSE benefit phosphorus absorption by their host plants remains unclear. Methods We established pot cultures and compartmentalized microcosms in the greenhouse and used transcriptomic analysis to examine the response of maize to inoculation with a DSE strain, Exophiala pisciphila H93, which has been found to be capable of promoting plant growth and enhancing the tolerance of maize to heavy metals. Results H93 promoted the biomass, phosphorus absorption and photosynthesis of inoculated maize by enhancing phosphorus enzyme activities in the rhizosphere and by decreasing the pH of the rhizosphere compared with non-inoculated controls, either in sufficient or deficient phosphorus conditions in pot cultures. H93 inoculation changed the transcriptional pattern of maize related to 8 metabolic pathways. While H93 did not induce particular phosphate transporter gene expression under deficient phosphorus conditions, it dissolved the sparingly soluble phosphates (tricalcium phosphate) in the rhizosphere. Conclusions Enhanced phosphorus absorption by the host plant by DSE (H93) seemed to occur independently of DSE-induced genes involved in phosphorus absorption. The greatest contribution of DSE to phosphorus utilization of hosts might be their efficiency in transferring sparingly soluble phosphorus into soluble phosphate (Pi).