Integrated biochemical and transcriptomic analysis reveals the effects of Burkholderia sp. SRB-1 on cadmium accumulating in Chrysopogon zizanioides L. under Cd stress

Application of plant growth-promoting rhizobacteria plays a vital role in enhancing phytoremediation efficiency. In this study, multiple approaches were employed to investigate the underlying mechanisms of Burkholderia sp. SRB-1 (SRB-1) on elevating Cd uptake and accumulation. Inoculation experiment indicated that SRB-1 could facilitate plant growth and Cd tolerance, as evidenced by the enhanced plant biomass and antioxidative enzymes activities. Cd content in plant shoots and roots increased about 36.56%-39.66% and 25.97%-130.47% assisted with SRB-1 when compared with control. Transcriptomics analysis revealed that SRB-1 upregulated expression of amiE, AAO1-2 and GA2-ox related to auxin and gibberellin biosynthesis in roots. Auxin and gibberellin, as hormone signals, regulated plant Cd tolerance and growth through activating hormone signal transduction pathways, which might also contribute to 67.94% increase of dry weight. The higher expression levels of ATP-binding cassette transporter subfamilies (ABCB, ABCC, ABCD and ABCG) in Chrysopogon zizanioides roots contributed to higher Cd uptake in Cd15 B (323.83 mg kg-1) than Cd15 (136.28 mg kg-1). Further, SRB-1 facilitated Cd migration from roots to shoots via upregulating the expression of Nramp, ZIP and HMA families. Our integrative analysis provided a molecular-scale perspective on Burkholderia sp. SRB-1 contributing to C. zizanioides performance.