Effect of crude oil pollution on heavy metal content and GST gene expression of Mucuna pruriens

Abstract

The study investigated the effect of crude oil pollution on the heavy metal content and gene expression of Mucuna pruriens. Varying amounts of crude oil (0ml, 200ml, 400ml, 800ml and 1000ml) were used to pollute 10kg bags of loam soil, onto which Mucuna pruriens seeds were planted for 8 weeks. Data were collected for heavy metal content of plant tissues and GST gene expression. The highest heavy metal content of the plant tissue was observed at the 800ml treatment (0.0135 g kg-1, 0.074 g kg-1, and 0.0211 g kg-1) and the least was observed for the control treatment (0.0049 g kg-1, 0.034 g kg-1 and 0.0142 g kg-1), thus showing percentage increments of 175.51%, 117.65%, and 48.59% for the copper, zinc, and nickel content respectively. This showed that the increment of crude oil pollution in the soil led to a seemingly dose-dependent increment of heavy metal content of the plant tissue. The normalized expression levels of the target gene (GST) in the calibrator (control) sample “A”, and that of the treated/polluted (test) sample “B” were established as 0.150726 and 0.145592 respectively; and, it was established that there was no significant change in the normalized expression levels of the target gene (GST) in both the control (calibrator) sample and the treated/polluted (test) sample. Crude oil treatment of M. pruriens, despite showing reductions in the morphological parameters and increments in the heavy metal content of the tissues, didn’t affect the expression of the target GST gene, as was evident in the absence of significant difference in the normalized expression levels of the target gene (GST) in both the control (calibrator) sample and the treated/polluted (test) sample. Considering the resilience of M. pruriens and its ability to adapt to the high amounts of crude oil in the soil, it is advised that it be employed in the possible phyto-extraction of crude oil and/or phyto-remediation in crude oil polluted soils.