Bacillus sp. WR12 alleviates iron deficiency in wheat via enhancing siderophore- and phenol-mediated iron acquisition in roots

Iron (Fe) deficiency seriously affects crop growth and yield. This study investigated whether and how an endophytic isolate, strain Bacillus sp. WR12, alleviates Fe deficiency in wheat (Triticum aestivum L.). Bacillus sp. WR12 and wheat seedlings were hydroponically co-cultured for 2 weeks under Fe-deficient conditions. To evaluate the Fe deficiency alleviating potential, wheat growth parameters were compared. To elucidate possible mechanisms, the genome of WR12 was sequenced, and production of siderophores was detected. In addition, transcriptomes of wheat root were compared, and accumulation of phenolic compounds was measured. Bacillus sp. WR12 significantly increased root length and dry weight, leaf chlorophyll content and Fe content in Fe-deficient wheat seedlings. Genome analysis of WR12 and CAS agar diffusion test demonstrated that WR12 had a dhbACEBF operon and produced siderophores. Significant upregulation of this operon and more siderophore synthesis in WR12 were observed when Fe was insufficient. Transcriptomic data of roots indicated change of expression of a large number of genes in Fe-deficient wheat after WR12 inoculation. Particularly, PAL, CYP73A, COMT, F5H, HCT and CAD genes involved in phenylpropane biosynthesis were significantly up-regulated. Moreover, elevated phenol accumulation was detected in the root of wheat after inoculation with WR12 under Fe deficiency. Bacillus sp. WR12 alleviates Fe deficiency in wheat and this can be partially attributed to enhanced siderophore production and phenol accumulation.