The biological role of free polyisoprenoid alcohols is uncertain but biophysical experiments have shown that isoprenoids increase the permeability and fluidity of the model membranes. In contrast to polyisoprenoid alcohols the biological role of prenylated quinones (plastoquinone-PQ and ubiquinone) is well established. Both are components of the electron transport machinery. Additionally both of them are postulated to function as antioxidants. There is a little information describing role of isoprenoids in the plant response to stress conditions (1) however the increase of biosynthesis of quinones under oxidative stress was observed (2). We tried to explain whether polyisoprenoids alcohols and PQ participate in defence mechanisms activated in plants upon various stress conditions. Virial (TMV-Tobacco Mosaic Virus) infection of tobacco plants was used as a model of biotic stress. In our experiments Nicotiana tabacum cv Samsun NN (resistant to TMV) was applied. The increase of solanesol (Sol), dolichol (Dol) and plastoquinone (PQ) content in TMV-infected leayes suggested the possible involvement of analyzed isoprenoids in plant response to viral infection. In parallel we analyzed activity of selected antioxidant enzymes, lipoxygenase (LOX) and lipid peroxidation in infected leaves. The increase of antioxidant enzyme activities and lipid peroxidation was observed directly after viral infection in contrast to LOX activity. It is widely accepted that SA plays central role in biotic stress signaling upon pathogen infection. We checked if SA is an inducer of isoprenoid accumulation. Tobacco leaves was sprayed with SA but the content of PQ, solanesol and dolichols remained unchanged. Similarly, after wounding, the changes of content of analyzed isoprenoids were not observed.

We also investigated the effect of sulphur starvation on the accumulation of isoprenoids in tobacco leaves (LA Burley 21),(3). The significant increase of PQ accompanied by a moderate increase of Sol content was observed. In contrast, Dol content was decreased.

The increase of PQ content observed upon TMV infection and sulphur starvation suggests its plausible role in plant defence mechanism, most probably as an element of the antioxidant system. Parallel increase of Sol level probably reflects the biosynthetic relationship between solanesyl diphospate (the precursor of PQ side chain) and PQ. Doubled amount of dolichols observed in infected tobacco leaves also suggests their role in plant.

1. Bajda, A. et al. 2005: Acta Biochim. Pol.52.

2. Wanke M. et al. Biochim. Biophys. Acta 1463 (2000) 188-194

3. Wawrzynska A. et al. J Exp Bot 2005 Jun; 56(416):1575-90

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1. Changes in polyisoprenoid alcohols accumulation upon abiotic stress in plants
2. Raman spectroscopy and morphology investigation of porous GaAs