Environmental and Experimental Botany 67 (2010) 487–494 Contents lists available at ScienceDirect Environmental and Experimental Botany journal homepage: www.elsevier.com/locate/envexpbot Aluminum stress induces up-regulation of an efficient antioxidant system in the Al-tolerant maize line but not in the Al-sensitive line A. Giannakoula a , M. Moustakas a,∗ , T. Syros b , T. Yupsanis b a Department of Botany, School of Biology, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece b Laboratory of Biochemistry, School of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece article info Article history: Received 7 May 2009 Received in revised form 17 July 2009 Accepted 20 July 2009 Keywords: Aluminum toxicity Antioxidants Carbohydrates Oxidative stress Peroxidase Proline Superoxide dismutase Zea mays L abstract The response of the antioxidant enzymes, superoxide dismutase (SOD; EC 1.15.1.1) and peroxidase (POD; EC 1.11.1.7), to Aluminum (Al) stress was studied in roots of two inbred lines of maize (Zea mays L.) dif- fering in their tolerance to Al. In addition, the production of malondialdehyde (MDA) was measured to evaluate the level of lipid peroxidation as well as the accumulation of proline (Pro) and carbohydrates under 72 h Al stress. Roots of Al (0, 120, 240, 360 and 480 M, at pH 4.2) -treated plants were sampled at various times (12, 24, 48, 72 h) after commencement of stress. A major difference in the antioxidant enzymes between the two maize lines associated with Al tolerance was observed after 24 h of Al exposure. A gradual increase in the membrane lipid peroxidation in Al-stressed root of the susceptible maize line was accompanied by decreased activities of the antioxidant enzymes SOD and POD. In contrast, increased activities of the SOD and POD were found in Al-treated roots of the tolerant maize line, in which the level of membrane lipid peroxidation remained almost unchanged. After 72 h exposure to 480 M Al the accu- mulation of Al in roots was almost from 90 times (tolerant) to 140 times (sensitive) than the control (without Al), while at the same time Al treatment resulted in 2.2 to 2.5-fold (at 240, 360 and 480 M Al) increased Pro content in the roots of the tolerant line compared to 0 M Al. Yet, 72 h exposure to 480 M Al increased 1.7-fold the carbohydrate concentration in the roots of the Al tolerant maize line VA-22 while in the sensitive line A 4/67 remained almost unchanged. These data provide evidence of an internal mech- anism of tolerance that increase the antioxidant system activity in order to limit cellular damages and possibly linked to the Al tolerance of the maize line VA-22. Analyses of the 12, 24, 48, and 72 h POD and SOD isoforms showed that in the Al-tolerant maize plants the anionic POD isoforms A 1 ,A 3 and A 4 and the SOD isoforms SOD 1 and SOD 2 were induced by increased Al-stress. It seemed that in the Al tolerant maize line, the anionic POD isoforms A 1 ,A 3 and A 4 and the SOD isoforms SOD 1 and SOD 2 were required for adap- tation as the oxidant level increased by the increased Al stress. Our results suggest that Al toxicity may be mediated by oxidative stress and that the better protection of the Al tolerant maize roots from Al-induced oxidative damage results, at least partially, from the increased activity of their antioxidative system. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Aluminum (Al 3+ ) toxicity limits plant productivity on acid soils and micromolar concentrations in the soil solution can rapidly inhibit root elongation and subsequently the uptake of water and nutrients, resulting in significant reduction of crop production on acid soils, which comprises 30–40% of the world’s arable soils (von Uexküll and Mutert, 1995). Inhibition of root elongation is Abbreviations: Al, aluminum; GB, glycine betaine; ICP-AES, inductively coupled plasma atomic emission spectrometry; MDA, malondialdehyde; PCD, programmed cell death; Pro, proline; POD, peroxidase; ROS, reactive oxygen species; SOD, super- oxide dismutase; TBA, thiobarbituric acid; TCA, trichloracetic acid. ∗ Corresponding author. Tel.: +30 2310 998335; fax: +30 2310 998389. E-mail address: moustak@bio.auth.gr (M. Moustakas). one of the most distinct and earliest symptoms of Al toxicity, which occurs within hours or even minutes of exposure to Al 3+ (Kochian et al., 2005). In plants growing in fields with subsoil acidity, the capacity to explore the soil for nutrients and water is substantially restricted. As a result, plants may suffer from severe water stress after only a few days without rainfall (von Uexküll and Mutert, 1995). The reduced volume of the root system may not be the only reason for Al-induced water deficiency in plants (Barceló and Poschenrieder, 1990). In addition to inhibition of root elongation and cell division (Doncheva et al., 2005), plants suf- fered from Al toxicity also display symptoms such as formation of barrel-shaped cells (Gunsé et al., 1997) and swelling of root apex ( ˇ Ciamporová, 2002). The primary mechanism underlying the Al 3+ -induced inhibition of root growth remains to be deciphered (Barceló and Poschenrieder, 2002; Jones et al., 2006; Sun et al., 2007). 0098-8472/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.envexpbot.2009.07.010