Cellular responses to naphthoquinones: juglone as a case study

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 (E m ), value of which was dependent on JG concentration and time after its administration. Hyperpolarization of E m 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.

Morpho-histological analysis of tomato (Solanum lycopersicum L.) plants after treatment with juglone

“…Analyses of the influence of juglone have also been the focus of studies on physiological parameters such as photosynthesis or mitochondria functioning and have indicated that juglone disturbs these physiological processes [3,4,22,27]. In the light of the above-mentioned studies, the results presented here, which show a positive influence of juglone on tomato plants, are rather unique.…”

“…In growth analyses, the treatment usually lasted several weeks and the effect was harmful [19,21,28]. In experiments in which the physiological response or gene expression was investigated, the treatment with juglone lasted only hours [3,4,29,30]. Therefore, it is difficult to compare our results with most of the literature data.…”

“…Seedlings were transferred to pots with a soil and vermiculite mixture (2:1 v/v) and grown at a temperature of 23 ±1°C, a relative humidity of 35% and a 16-h photoperiod with a light intensity of 40 μmol m −2 s −1 (cool white fluorescence lamp; OSRAM). Plants were watered every 2 days with Hoagland's solution [4]. For each experiment, 28-day-old plants were used.…”

“…It has been shown that juglone can inhibit the growth of shoots and roots and that it also interferes with photosynthesis and transpiration processes. Despite the large amount of published data concerning the biological activity of juglone, little is known about the mechanisms of its toxic effects on plant growth [2,4,5]. Studies on corn and soybean showed that juglone is responsible for the inhibition of plasma membrane H + -ATPase, resulting in the inhibition of the uptake of water and nutrients by the roots (for review see [5]).…”

A comparison of the effects of 1,4-naphthoquinone and 2-hydroxy-1,4-naphthoquinone (lawsone) on indole-3-acetic acid (IAA)-induced growth of maize coleoptile cells

“…Recently, we showed that juglone (5-hydroxy-1,4-naphthoquinone), which is a naturally occurring naphthoquinone in walnut trees (Juglans), inhibited both IAA-induced growth and proton extrusion in maize coleoptile cells in a concentration-dependent manner. The strong correlation between both of these magnitudes suggested that the mechanism by which juglone inhibits IAA-induced growth involves the inhibition of PM H + -ATPase activity (Rudnicka et al 2014). Quite recently, Kurtyka et al (2016) published a paper in which the authors obtained that juglone and lawsone contribute to H 2 O 2 generation and activity of ROS scavenging enzymes (SOD, POX and CAT) in maize coleoptile segments.…”