Cellular responses to naphthoquinones: juglone as a case study

M Rudnicka,W Karcz,M Polak

doi:10.1007/s10725-013-9855-y

Abstract

The effects of juglone (JG) on the endogenous growth, growth in the presence of either indoleacetic acid (IAA) or fusicoccin (FC) and on proton extrusion were studied in maize coleoptile segments. In addition, membrane potential changes were also determined at chosen JG concentrations. It was found that JG, when added to the incubation medium, inhibited endogenous growth as well as growth in the presence of either IAA or FC. Simultaneous measurements of growth and external pH indicated that inhibition of either IAA-induced growth or proton extrusion by JG was a linear function of JG concentration. Addition of JG to the control medium caused depolarization of the membrane potential (Em), value of which was dependent on JG concentration and time after its administration. Hyperpolarization of Em induced by IAA was suppressed in the presence of JG. It was also found that for coleoptile segments initially preincubated with JG, although subsequently removed, addition of IAA was not effective in the stimulation of growth and medium acidification. Taken together, these results suggest that the mechanism by which JG inhibits the IAA-induced growth of maize coleoptile segments involves inhibition of PM H+-ATPase activity.

Highlights

Occurring naphthoquinones, such as juglone (JG) (5-hydroxy-1,4-naphthoquinone), lawsone (2-hydroxy-1,4naphthoquinone), plumbagin (2-methyl-5-hydroxy-1,4naphthoquinone) and others, have been studied for a long time due to their importance in medicinal and biological research (O’Brien 1991; Jose 2002; Dayan and Duke 2009)
The effects of juglone (JG) on the endogenous growth, growth in the presence of either indoleacetic acid (IAA) or fusicoccin (FC) and on proton extrusion were studied in maize coleoptile segments
These results suggest that the mechanism by which JG inhibits the IAA-induced growth of maize coleoptile segments involves inhibition of PM H?-ATPase activity

Summary

Introduction

Occurring naphthoquinones, such as juglone (JG) (5-hydroxy-1,4-naphthoquinone), lawsone (2-hydroxy-1,4naphthoquinone), plumbagin (2-methyl-5-hydroxy-1,4naphthoquinone) and others, have been studied for a long time due to their importance in medicinal and biological research (O’Brien 1991; Jose 2002; Dayan and Duke 2009). In agreement with the definition recently proposed by Dayan and Duke (2009), the word allelochemical means a phytotoxin that may negatively influence vegetation in the vicinity of the producing plant. In spite of the large number of papers published on the biological activity of JG (for review see Jose 2002; Dayan and Duke 2009), little is

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