REPETITIVE/NON CODING DNA: A NEW, RAPID AND EARLIER KIND OF BIOMARKER

In this paper, we propose a different kind of biomarker for environmental stress presenting new and important advantages: the repetitive/non-coding DNA. This is DNA that is not even transcribed, but that reacts to environmental stresses by selective amplifications of some of its sequences. This DNA reaction is immediate and quantitatively significant: it is a preliminary response of DNA to stresses, a response that is preparatory to other successive molecular events. Our idea is to exploit such a genomic "alarm-bell", in order to develop a new and earlier kind of biomarker. In this context, we propose to utilize the repetitive DNA of the Bryophytes: in fact. the peculiar structure of their genome allows detection of the repetitive DNA variations directly in situ, by rapid and inexpensive cyto-molecular techniques. In particular, we have analysed the cadmium or lead-induced repetitive DNA behaviour in Funaria hygrometrica using different experimental approaches. The cytomolecular results showed that lead or cadmium stress induces a selective G-C-rich repetitive DNA amplification that is proportional to the time of moss exposition to metals, and that stops after removing the metals from the culture medium. Biochemical analyses showed that this metal-induced repetitive DNA is only partially made up of ribosomal DNA sequences. Finally, TEM X-ray microanalyses have shown that the metals are able to enter the nucleus and locate precisely in the heterochromatic areas of DNA. Present data show that the exploitation of repetitive/non-coding DNA as a biomarker could open the way to a new. earlier, rapid, inexpensive and meaningful monitoring of environmental pollution effects.