Effects of Manganese on the Antioxidant System and Related Gene Expression Levels in the "Hong Yang" Kiwifruit Seedlings

To explore how manganese affects the antioxidant system and the expression levels of related genes of "Hong yang" seedlings, the leaves of its tissue cultured seedlings were taken as test materials, and single factor treatment was performed by changing the manganese chloride (MnCl2.4H2O) solution concentration when spraying the leaves. The expression levels of Mn-SOD, POD64 and POD27 genes in leaves were quantitatively analyzed by real-time quantitative PCR (qRT-PCR) at different determination times. Meanwhile, the contents of malondialdehyde (MDA), hydrogen peroxide (H2O2), the activities of antioxidant enzymes, including catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD). The results showed that the SOD, CAT, POD, ascorbate peroxidase (APX), and reduced glutathione (GSH) activities in leaves were the highest at 12 h post-treatment with 50 & mu;M MnCl2 & BULL;4H2O. Furthermore, the contents of MDA and H2O2 in leaves also peaked when the concentration of H2O2 is 50 & mu;M, which is the minimum value. Additionally at 50 & mu;M Mn2+, the Mn-SOD and POD27 expression was up-regulated as compared to the control, which promoted the expression of their respective enzyme activities. However, POD64 expression increased with the increasing Mn2+ concentration. Therefore, 50 & mu;M is the optimal concentration of Mn when exogenously applied on "Hong yang", which improve the antioxidant enzyme activity and regulate the plant's physiological and biochemical functions.