The influence of selenium on expression levels of the rbcL gene in Chlorella vulgaris

Abstract

In this study, the effects of selenium on the microalgae Chlorella vulgaris were examined. Four groups of C. vulgaris were cultivated using Bristol medium: group I (control), no sodium selenite (Se); group II, 1 mu M Se; group III, 10 mu M Se; and group IV, 100 mu M Se. Algal biomass samples were collected for biochemical evaluation and gene expression studies on the 21st day of cultivation. The following parameters were investigated: chlorophyll a (Cl-a), chlorophyll b (Cl-b) and total carotene content, total protein, and total glutathione (GSH) and malondialdehyde (MDA) levels. Gene expression levels of large subunits of Rubisco (rbcL) were analyzed using real-time quantitative polymerase chain reaction. Total Cl-a and total carotene in C. vulgaris decreased in high concentrations of Se (100 mu M) (around 23 and 42%, respectively) when compared to controls while, Cl-b content increased by about 10%. 10 mu M of Se led to increased GSH levels (3.04 +/- 0.02 mu g GSH/mg protein) and decreased MDA levels (2.02 +/- 0.1 mu mol MDA/mg protein) when compared to control groups (1.18 +/- 0.04 mu g GSH/mg protein and 0.94 +/- 0.23 mu mol MDA/mg protein), while a significant decrease in GSH and an increase in MDA levels in the presence of 100 mu M Se showed the opposite effect. rbcL gene expression increased 1.76 +/- 1.37-fold and 0.86 +/- 1.33-fold in 10 and 100 mu M selenium experiments when compared to control groups. Our results suggest both pro-oxidant and antioxidant activities of Se on C. vulgaris and upregulation of the rbcL gene for the first time. Treatment with low concentrations of Se improves the antioxidant features of the microalgae, C. vulgaris.