Potential effects of prolonged ultraviolet radiation exposure in plants: chloroplast DNA analysis

Abstract

The present study on the Namaqualand daisy, Dimorphotheca sinuata sought to address two main questions: - first whether the natural populations show any evidence of variation in the chloroplast genome, and secondly if the changes could be attributed to prior damage by UV-B i.e. via the formation of pyrimidine dimers at some some stage in their history. Characterization of chlroplast DNA from natural plant populations of D. sinuata across a latitudinal gradient was carried out using restriction endonuclease digestion. The enzymes used included DraI (TTTAAA), EcorI (GAATTC) and HindIII (AAGCTT) whose recognition sequences are possible targets for UV-B radiation, and BamHI (GGATCC) and EcoRV (GATATC) whose recognition sequences are not obvious UV-B targets. Plants growing at northern latitudes (potentially higher UV-B environments) revealed striking polymorphisms that may be attributed to genome re-arrangements resulting from UV-B stress when compared with plants from southern latitudes (lower UV-B environments). This is the first known attempt at developing a southern African biological method for predicting long-term effects of ozone depletion, and the resultant rise in Uv-B radiation, on our indigenous flora.