The Endophytic Fungus Piriformospora Indica-Assisted Alleviation of Cadmium in Tobacco

Abstract

Increasing evidence suggests that the endophytic fungus Piriformospora indica helps plants overcome various abiotic stresses, especially heavy metals. However, the mechanism of heavy metal tolerance has not yet been elucidated. Here, the role of P. indica in alleviating cadmium (Cd) toxicities in tobacco was investigated. It was found that P. indica improved Cd tolerance to tobacco, increasing Cd accumulation in roots but decreasing Cd accumulation in leaves. The colonization of P. indica altered the subcellular repartition of Cd, increasing the Cd proportion in cell walls while reducing the Cd proportion in membrane/organelle and soluble fractions. During Cd stress, P. indica significantly enhanced the peroxidase (POD) activity and glutathione (GSH) content in tobacco. The spatial distribution of GSH was further visualized by Raman spectroscopy, showing that GSH was distributed in the cortex of P. indica-inoculated roots while in the epidermis of the control roots. A LC-MS/MS-based label-free quantitative technique evaluated the differential proteomics of P. indica treatment vs. control plants under Cd stress. The expressions of peroxidase, glutathione synthase, and photosynthesis-related proteins were significantly upregulated. This study provided extensive evidence for how P. indica enhances Cd tolerance in tobacco at physiological, cytological, and protein levels.

Fungal Endophytes as Mitigators against Biotic and Abiotic Stresses in Crop Plants

“…In this context, fungal endophytes and plants have symbiotic relationships that are essential for enhancing the activity of antioxidant enzymes through heavy metal uptake from soil, followed by detoxifying the deleterious effects of heavy metal stress in plants [153][154][155]. It was observed that P. indica enhanced the resistance of N. tabacum plants to cadmium stress by upregulating the expression of photosynthesis-related proteins, GS, and POD to lessen the oxidative damage that cadmium causes [156]. Musa et al [157] described that endophytic Paecilomyces lilacinus inoculation produces greater amounts of indole acetic acid and secondary metabolites that have an immense potential to promote S. lycopersicum plant growth and alleviate the adverse effects of heavy metal (such as cobalt and lead) stress conditions.…”

Coumarins as Fungal Metabolites with Potential Medicinal Properties

“…Reliable evidence has been obtained to suggest that at least a few endophytes have such roles as protecting plants against phytopathogens, enhancing the host plant’s tolerance to abiotic stresses [ 44 ], etc. Endophytes are capable of enhancing a host’s resistance against herbivores, insects, other pathogens, drought, variations in temperature and salinity, and heavy metal stress [ 45 ], since these fungi can biotransform inorganic and organic low-molecular-weight chemical agents along with macromolecules (heavy metal compounds, toxins, and other pollutants) [ 46 ]. Prolonged and sustained responsive mechanisms of endophytic fungus developed to withstand the host plant’s defense were proposed to act as selection pressure for establishing novel metabolic pathways [ 47 ].…”

Diversity, detection and exploitation: linking soil fungi and plant disease

“…Finally, plant-associated fungi can indirectly promote plant health, and hence pathogen defence by bolstering responses to abiotic stressors, including temperature, salinity, toxic compounds and heavy metal contamination, drought and flooding. For example, Su and coworkers recently defined the mechanism of Piriformospora alleviation of cadmium stress in tobacco and showed that P. indica colonisation systemically enhances Cd tolerance at physiological, cytological and protein levels [26]. Inoculation with P. indica markedly improved the Cd tolerance of tobacco, with increased Cd accumulation in the cortex, as opposed to the epidermis, of roots and decreased accumulation in leaves.…”

“…P. indica colonisation apparently alters the subcellular repartition of Cd, with increased Cd accumulation in cell walls and reduced levels in membranes, organelles and soluble fractions of plant cells. P. indica further enhanced the content of antioxidant glutathione (GSH) and activity of peroxidase enzyme (POD) and the expression of photosynthesis-related proteins in response to tobacco Cd stress [26].…”