Potential of uv radiation protection by the expression of drwh gene and antioxidant related genes of deinococcus radiodurans R1

The prolonged exposure to sunlight is detrimental for the cells as they are exposed to high energy electromagnetic radiation from ultraviolet (UVA: 320 – 400 nm; UVB: 290 – 320 nm; UVC: 200 – 290 nm). UV radiation (UVR) can directly or indirectly affect vital biomolecules by producing reactive oxygen species (ROS). It is known that Deinococcus radiodurans R1 (D. radiodurans R1) can tolerate high amount of UVR. One of the reasons for the tolerance by D. radiodurans R1 apart from its powerful gene repair and the presence of carotenoid is due to the high expression of drwH gene that encodes for LEA protein upon exposure to UVR. The expression of drwH gene affecting the amount of ROS quantified using 2’,7’-dichlorodihydrofluorescein diacetate (DCFH-DA) in D. radiodurans R1 because high expression of drwH gene is able to lowering down the level of ROS in the cells. High expression of drwH gene after UVC radiation also affecting the cell viability of D. radiodurans R1 as the percentage of bacterial cells killed after UVC radiation is lower as compared to UVA radiation. Total RNA is extracted from D. radiodurans R1 after irradiation to examine the expression fold changes of drwH gene and other antioxidant related genes that encode for antioxidant enzymes like superoxide dismutase, catalase and peroxidase by using RT-qPCR technique. LEA protein is believed to function as a chaperone or molecular shield to other proteins. Therefore, it is valuable to know whether drwH gene is able to affect the expression of antioxidant related genes. The expression fold of drwH gene is high after UVC radiation as compared to UVA radiation with the highest amount of 240.03 fold at 12 h of UVC radiation but lowest at 6 h with the value of 92.86 fold. The lower expression fold changes at 6 h of UVC radiation might be explain by higher expression fold changes of antioxidant related genes during that time. However, the expression of drwH gene does not explain the effect on antioxidant related genes, but the increased of both expressions lowered the level of ROS and preventing the decreased in cell viability. Then, drwH gene is cloned into Escherichia coli (E. coli) BL21 (DE3) but the difference in cell viability between wild type and recombinant BL21 is little after UVA radiation but after UVC radiation, the cell viability of recombinant E. coli BL21 (DE3) is higher than wild type E. coli BL21 (DE3) after 12 h of irradiation. In conclusion, drwH gene is capable to provide protection against a high energy UVR and increased the viability of the cells as compared to low energy UVR. High expression fold of drwH gene and antioxidant related genes might lowering down the level of ROS production after UV radiation and this is contributing to the new insight on the dynamics of ROS and drwH gene relationship.

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