Endophytic Penicillium funiculosum LHL06 secretes gibberellin that reprograms Glycine max L. growth during copper stress.

BACKGROUND

Heavy metal pollution in crop fields is one of the major issues in sustainable agriculture production. To improve crop growth and reduce the toxic effects of metals is an ideal strategy. Understanding the resilience of gibberellins producing endophytic fungi associated with crop plants in metal contaminated agriculture fields could be an important step towards reducing agrochemical pollutions. In present study, it was aimed to screen and identify metal resistant endophyte and elucidate its role in rescuing crop plant growth and metabolism during metal stress.

RESULTS

Fungal endophyte, Penicillium funiculosum LHL06, was identified to possess higher growth rate in copper (Cu) and cadmium contaminated mediums as compared to other endophytes (Metarhizium anisopliae, Promicromonospora sp. and Exophiala sp.). P. funiculosum had high biosorption potential toward copper as compared to cadmium. An endophyte-metal-plant interaction was assessed by inoculating the host Glycine max L. plants with P. funiculosum during Cu (100 μM) stress. The Cu application adversely affected the biomass, chlorophyll and total protein content of non-inoculated control plants. The control plants unable to synthesis high carbon, hydrogen and nitrogen because the roots had lower access to phosphorous, potassium, sulphur and calcium during Cu treatment. Conversely, P. funiculosum-association significantly increased the plant biomass, root physiology and nutrients uptake to support higher carbon, hydrogen and nitrogen assimilation in shoot. The metal-removal potential of endophyte-inoculated plants was significantly higher than control as the endophyte-association mediated the Cu uptake via roots into shoots. The symbiosis rescued the host-plant growth by minimizing Cu-induced electrolytic leakage and lipid peroxidation while increasing reduces glutathione activities to avoid oxidative stress. P. funiculosum-association synthesized higher quantities of proline and glutamate as compared to control. Stress-responsive abscisic acid was significantly down-regulated in the plant-metal-microbe association.

CONCLUSIONS

The endophyte P. funiculosum symbiosis counteracted the Cu stress and reprogrammed soybean plant growth. Such growth promoting and stress mediating endophytes can be applied at field levels to help in bioremediation of the polluted agricultural fields.