title: Effects of juglone and lawsone on oxidative stress in maize coleoptile cells treated with IAA.
abstract: Naphthoquinones are secondary metabolites widely distributed in nature and produced by bacteria, fungi and higher plants. Their biological activity may result from induction of oxidative stress, caused by redox cycling or direct interaction with cellular macromolecules, in which quinones act as electrophiles. The redox homeostasis is known as one of factors involved in auxin-mediated plant growth regulation. To date, however, little is known about the crosstalk between reactive oxygen species (ROS) produced by quinones and the plant growth hormone auxin (IAA). In this study, redox cycling properties of two naphthoquinones, juglone (5-hydroxy-1,4-naphthoquinone) and lawsone (2-hydroxy-1,4-naphthoquinone), were compared in experiments performed on maize coleoptile segments incubated with or without the addition of IAA. It was found that lawsone was much more effective than juglone in increasing both H2O2production and the activity of antioxidative enzymes (SOD, POX and CAT) in coleoptile cells, regardless of the presence of IAA. An increase in the activity of Cu/Zn-SOD isoenzymes induced by both naphthoquinones suggests that juglone- and lawsone-generated H2O2was primarily produced in the cytosolic and cell wall spaces. The cell potential to neutralize hydrogen peroxide, determined by POX and CAT activity, pointed to activity of catalase as the main enzymatic mechanism responsible for degradation of H2O2Therefore, we assumed that generation of H2O2, induced more efficiently by LW than JG, was the major factor accounting for differences in the toxicity of naphthoquinones in maize coleoptiles. The role of auxin in the process appeared negligible. Moreover, the results suggested that oxidative stress imposed by JG and LW was one of mechanisms of allelopathic action of the studied quinones in plants.
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40 032 Katowice, Poland renata.kurtyka@us.edu.pl.
authors.forename: Renata
authors.initials: R
authors.lastname: Kurtyka
authors.affiliation: Department of Plant Physiology and Biotechnology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, PL-80 308 Gdańsk, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Pokora
authors.affiliation: Department of Plant Physiology and Biotechnology, Faculty of Biology, University of Gdańsk, Wita Stwosza 59, PL-80 308 Gdańsk, Poland.
authors.forename: Zbigniew
authors.initials: Z
authors.lastname: Tukaj
authors.affiliation: Department of Plant Physiology, Faculty of Biology and Environmental Protection, University of Silesia, Jagiellońska 28, PL-40 032 Katowice, Poland.
authors.forename: Waldemar
authors.initials: W
authors.lastname: Karcz
keywords: Coleoptile segments; Zea mays; juglone; lawsone; oxidative stress