Mechanisms of Cr(VI) resistance by endophytic Sphingomonas sp. LK11 and its Cr(VI) phytotoxic mitigating effects in soybean (Glycine max L.)

• Published in: Ecotoxicology and environmental safety Vol. 164; pp. 648 - 658
• Main Authors: Bilal, Saqib, Khan, Abdul Latif, Shahzad, Raheem, Kim, Yoon-Ha, Imran, Muhammad, Khan, Muhammad Jamil, Al-Harrasi, Ahmed, Kim, Tae Han, Lee, In-Jung
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier Inc 30.11.2018
• Subjects: abscisic acid; Abscisic Acid - metabolism; antioxidants; bioremediation; catalase; Catalase - metabolism; chromium; Chromium - toxicity; Chromium stress; crops; Crops, Agricultural - drug effects; Crops, Agricultural - metabolism; Crops, Agricultural - microbiology; Endophytes; energy-dispersive X-ray analysis; glutathione; Glutathione - metabolism; Glycine max; Glycine max - drug effects; Glycine max - metabolism; Glycine max - microbiology; homeostasis; IAA; indole acetic acid; Indoleacetic Acids - metabolism; leaves; lipid peroxidation; Lipid Peroxidation - drug effects; Oxidative stress; Oxidative Stress - drug effects; peroxidase; Peroxidase - metabolism; phenotypic plasticity; Phytohormones; phytotoxicity; Plant Development - drug effects; plant growth; Plant Growth Regulators - metabolism; Plant Leaves - drug effects; Plant Leaves - metabolism; Plant Leaves - microbiology; Plant Roots - drug effects; Plant Roots - metabolism; Plant Roots - microbiology; Plant Shoots - drug effects; Plant Shoots - metabolism; Plant Shoots - microbiology; polluted soils; Remediation; roots; salicylic acid; Salicylic Acid - metabolism; scanning electron microscopy; screening; SEM-EDX; Soil Pollutants - toxicity; Soybean; soybeans; Sphingomonas; Sphingomonas - metabolism; superoxide dismutase; Superoxide Dismutase - metabolism; Up-Regulation; Oxidative stress; SEM-EDX; Chromium stress; Endophytes; IAA; Phytohormones; Remediation; Soybean
• ISSN: 0147-6513; 1090-2414; 1090-2414
• DOI: 10.1016/j.ecoenv.2018.08.043

Chromium Cr(VI) is highly toxic and leads to impaired phenotypic plasticity of economically important crops. The current study assessed an endophytic-bacteria assisted metal bio-remediation strategy to understand stress-alleviating mechanisms in Glycine max L (soybean) plants inoculated with Sphingomonas sp. LK11 under severe Cr(VI) toxicity. The screening analysis showed that high Cr concentrations (5.0 mM) slightly suppressed LK11 growth and metal uptake by LK11 cells, while significantly enhancing indole-3-acetic acid (IAA) production. Endophytic LK11 significantly upregulated its antioxidant system compared to control by enhancing reduced glutathione (GSH), catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities to counteract Cr-induced oxidative stress. Cr toxicity induced cell morphological alteration, as shown by SEM-EDX analysis and triggered significant lipid peroxidation. The interaction between LK11 and soybean in Cr-contaminated soil significantly increased plant growth attributes and down-regulated the synthesis of endogenous defense-related phytohormones, salicylic acid and abscisic acid, by 20% and 37%, respectively, and reduced Cr translocation to the roots, shoot, and leaves. Additionally, Cr-induced oxidative stress was significantly reduced in LK11-inoculated soybean, regulating metal responsive reduced GSH and enzymatic antioxidant CAT. Current findings indicate that LK11 may be a suitable candidate for the bioremediation of Cr-contaminated soil and stimulation of host physiological homeostasis. •Endophytic LK11 act as an alternative strategy for alleviating chromium stress from soybean.•IAA producing capability of LK11 was remarkably upregulated Under chromium stress.•LK11 assoiciation promoted host plant growth attributes and modulated endogenous hormones and antioxidants.•LK11 Inoculated soybean displayed reduced accumulation of chromium.