Lead contamination reduces chlorophyll biosynthesis and genomic template stability in Brassica rapa L.

Abstract

In recent years, multiple biomarker systems have been frequently used to measure the genotoxic effects of environmental pollutants on living organisms. In this research, fodder turnip ( Brassica rapa L.) seedlings exposed to 0.5–5 mM concentrations of lead nitrate were used to evaluate the alterations in δ-aminolevulinic acid (ALA) level, δ-aminolevulinic acid dehydratase (ALAD) activity, photosynthetic pigments content (chlorophyll a, chlorophyll b and carotenoid) and random amplified polymorphic DNA (RAPD) profiles. Analytical studies by inductively coupled plasma optical emission spectrometry (ICP-OES) demonstrated that lead (Pb) accumulation in the roots and above ground parts of the seedlings increases with an increase in Pb concentration. Lead-induced toxicity resulted in the build-up ALA and reduced activity of ALAD, and photosynthetic pigments content in the leaves. For the RAPD analyses, 11 RAPD primers of 60–70% GC content were found to produce unique polymorphic band profiles and subsequently were used to produce a total of 126 bands of 189–2928 bp. The changes occurring in RAPD profiles of the leaves following Pb treatment included variation became evident as disappearance and/or appearance of DNA bands compared with the normal seedlings. It was found that the effect of changes was dose-dependent. These results indicated that genomic template stability was significantly affected at all Pb concentrations tested. The general tendency of genomic template stability, ALAD activity and photosynthetic pigments content of the leaves was a gradual decrease with an increase in Pb concentration. We concluded that RAPD analysis in conjunction with chlorophyll biosynthesis would a powerful ecotoxicological tool in biomonitoring of heavy metal pollution.