The effect of cadmium and zinc and their mixtures on genome stability in tobacco seedlings

Metali su prirodna sastavnica Zemljine kore, ali njihova koncentracija u okolišu se neprestano povećava uslijed antropogenih utjecaja. Teški metali mogu uzrokovati direktna i indirektna oštećenja važnih bioloških molekula, a njihova akumulacija u hranidbenom lancu predstavlja opasnost za sve organizme u okolišu. Cilj istraživanja bio je utvrditi učinak teških metala, kadmija i cinka te njihovih smjesa na stabilnost genoma klijanaca duhana Nicotiana tabacum L.. Cink i kadmij su kemijski vrlo slični teški metali pa kadmij može ometati vitalne, biološke reakcije u biljkama, zamjenjujući cink. Iako je pojedinačni utjecaj tih metala u biljnim organizmima detaljno istražen, njihovo međudjelovanje nije dovoljno poznato. U tu svrhu klijanci duhana su rasli mjesec dana na hranjivim podlogama uz dodatke različitih koncentracija metala i njihovih kombinacija. Razina oštećenja i promjene u molekuli DNA duhana nakon tretmana su procijenjeni metodom komet-testa i metodom nasumično umnožene polimorfne DNA (RAPD, engl. Random Amplified Polymorphic DNA). Iako su rezultati komet-testa pokazali oštećenje DNA djelovanjem teških metala kadmija i cinka na klijancima duhana, svakog zasebno i u kombinaciji, rezultati metode RAPD nisu pokazali promjenu u polimorfizmu DNA u niti jednom od tretmana. Komet-test se pokazao kao osjetljivija metoda pri detekciji oštećenja DNA nastalih teškim metalima za razliku od metode RAPD. Metals are natural components of the Earth’s crust but their concentration is constantly increasing due to anthropologic influences. Heavy metals can cause direct and indirect damages of vital biological molecules and their accumulation in the food chain is an immediate menace for all organisms in the environment. The objective of this research was to determine the effect of heavy metals, cadmium and zinc and their mixtures on the genome stability of tobacco seedlings. Even though the influences of these metals alone in plant organisms are researched in great detail, their interaction is not well known. Since zinc and cadmium are chemically very similar heavy metals, cadmium can interfere in vital, biological reactions inside the plants by replacing zinc. Seedlings were grown for 30 days on nutrient medium with addition of different metal concentrations and their mixtures. The extent of DNA damage and DNA alterations after the treatment were evaluated using the Comet assay and RAPD (Random Amplified Polymorphic DNA) method. Even though the results of Comet assay showed statistically significant DNA damage caused by heavy metals, individually and in mixtures, the results of RAPD analysis did not show any change in DNA polymorphism in all of the treatments. Comet assay proved to be a more sensitive method in detection of DNA damages caused by heavy metals in comparison to RAPD analysis.