Molecular and Biochemical Studies on the Effect of Gamma Rays on Lead Toxicity in Cowpea (Vigna sinensis) Plants

The effect of lead acetate in the presence or absence of cowpea seeds irradiated with gamma rays on morphological criteria, protein electrophoresis, isozymes, and random amplification of polymorphic DNA-polymerase chain reaction (RAPD-PCR) of leaves was investigated. A highly significant decrease in shoot and root length was observed upon lead acetate exposure (300 and 600 μM). On the other hand, in seeds irradiated with gamma rays (2, 5, and 8 krad), these morphological parameters were increased after lead acetate treatments. Meanwhile, all treatments (lead acetate and gamma rays) caused variations in number, intensity, and/or density of SDS electrophoretic bands of proteins. In addition, electrophoretic studies of esterase, acid phosphatase, peroxidase, polyphenol oxidase, catalase, and superoxide dismutase isozyme activities were increased with increasing the concentrations of lead acetate and gamma ray doses. The variation in DNA profile in response to lead acetate and gamma irradiation treatments was detected by RAPD-PCR technique. The result of RAPD analysis using the five primers indicated the appearance and disappearance of DNA polymorphic bands at all treatments (gamma rays and lead stress). The relatively high concentrations of lead acetate (600 μM) induced more changes in genomic DNA pattern.