Effect of silver nanoparticles on oxidative stress and protein expression in tobacco (Nicotiana tabacum)

Abstract

Klijanci i odrasle biljke duhana (Nicotiana tabacum L.) izloženi su tretmanima s nanočesticama srebra (AgNP) i ionskim srebrom (AgNO3) u koncentracijama od 25, 50, 75, 100 i 500 μM. Nakon tretmana s AgNP u klijancima je unatoč nižem sadržaju srebra utvrđen oksidacijski stres te promjene u aktivnosti i ekspresiji antioksidacijskih enzima, dok u odraslim biljkama nije bilo većih promjena. Tretmani s AgNO3 izazvali su pojavu oksidacijskog stresa i u klijancima i u korijenu odraslih biljaka, što pokazuje da je ionski oblik srebra toksičniji za duhan od nanočestica. U listovima biljaka tretiranih s AgNP i AgNO3 izostanak izraženijih toksičnih učinaka te niski sadržaj srebra upućuju na zaključak da se akumulacijom srebra u korijenu i sprečavanjem njegovog prijenosa u izdanak štiti fotosintetsko tkivo lista. Oba tipa tretmana dovela su do promjene u ekspresiji većeg broja proteina u klijancima nego u odraslim biljkama. Proteini su u najvećoj mjeri pripadali kategorijama Energija, Metabolizam te Odgovor na biotički i abiotički stres. Većina diferencijalno eksprimiranih proteina klijanaca imala je pojačanu ekspresiju, dok je ekspresija proteina korijena i lista uglavnom bila smanjena. Dobiveni rezultati impliciraju aktivaciju različitih mehanizama obrane u odgovoru duhana na izlaganje srebru, što ovisi o starosti tkiva, stupnju razvitka te duljini izlaganja srebru.Seedlings and adult tobacco (Nicotiana tabacum L.) plants were exposed to 25, 50, 75, 100 and 500 μM silver nanoparticles (AgNP) and ionic silver (AgNO3). After treatment with AgNP, oxidative stress and changes in antioxidant enzymes activity and expression were found in seedlings despite the lower Ag content, while in adult plants no major changes were observed. Treatments with AgNO3 induced prominent oxidative stress in seedlings and root of adult plants, indicating that silver in ionic form is more toxic for tobacco than nanoparticles. Treatments with AgNP and AgNO3 resulted with absence of toxic effects in leaf, which together with a low Ag content suggests that Ag accumulation in root and the prevention of its transfer to shoots protects the leaf photosynthetic tissue. Both types of treatment have induced changes in expression of a greater number of proteins in seedlings than in adult plants. Majority of identified proteins belonged to the Energy, Metabolism and Response to biotic and abiotic stress categories. Most of the differentially expressed proteins of seedlings were up-regulated, while the expression of root and leaf proteins was mainly reduced. The results imply activation of various defence mechanisms in tobacco in response to Ag, which depend on the age of tissue, stage of its development and the length of Ag exposure