Exogenous cysteine alleviates mercury stress by promoting antioxidant defence in maize
(<i>Zea mays</i> L.) seedlings

FERHUNDE AYSİN; AYKUT KARAMAN; ASLI YILMAZ; ÖZKAN AKSAKAL; EBRU GEZGİNCİOĞLU; SAKINEH MOHAMMADI KOHNEHSHAHRI

Exogenous cysteine alleviates mercury stress by promoting antioxidant defence in maize (Zea mays L.) seedlings

Authors: FERHUNDE AYSİN, AYKUT KARAMAN, ASLI YILMAZ, ÖZKAN AKSAKAL, EBRU GEZGİNCİOĞLU, SAKINEH MOHAMMADI KOHNEHSHAHRI

Abstract: Mercury (Hg) is one of the most important environmental pollutants that negatively affects plant growth and development. Cysteine (Cys) plays an important role in plant response to various environmental stress factors. In the present study, the alleviation of Hg stress through exogenous Cys treatment to maize seedlings was evaluated. For this purpose, a hydroponic experiment was set up to investigate the effect of HgCI₂ (100 μM) and in combination with Cys (200 μM) on plant growth, total chlorophyll content, reactive oxygen species, antioxidant enzyme activities, and mRNA expression levels of some antioxidant genes in maize seedlings. The results showed that HgCI₂ treatment significantly decreased both root and shoot growth and total chlorophyll content, also increased the malondialdehyde (MDA), hydrogen peroxide (H₂O₂), and superoxide levels (O₂ .-) in maize seedlings. After treatment with 200 μM exogenous Cys combined with 100 μM HgCl₂, root and shoot growth and total chlorophyll content increased and the concentration of MDA, H₂O₂, O₂ .- in seedlings notably decreased and catalase (CAT), glutathione reductase (GR), superoxide dismutase (SOD), and peroxidase (POD) activities in seedlings increased significantly. In addition, HgCI₂ treatment alone or combination with Cys markedly increased the root and leaf Hg content. The higher amounts of Hg accumulated in the roots of the seedlings. Furthermore, qRT-PCR results showed that the mRNA levels of CAT, GR, and SOD genes were up-regulated at HgCI₂ + Cys treatment groups compared to the HgCI₂ treatment alone. The results of the study indicated that exogenous Cys improved resistance to Hg-stress in maize seedlings by activating antioxidant defence system.

Keywords: Antioxidant, cysteine, gene expression, glutathione, mercury

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