11. Chronobiological phenomena and seasonal changes in jasmonate levels during the course of the year and under constant conditions in mistletoe (Viscum album L.).

Viscum album L. is used as an anti-tumour remedy. Some compounds present in mistletoe show large seasonal variations correlating with distinct chronobiological phenomena. During the heterochronical cycle of bifurcated shoot development mistletoe plants show nutational movements with circadian periods and higher amplitude nutations with periods of up to 78 h. Both exogenous and endogenous factors seem to control these movements. During summertime, in the final stages of the nutational movements, the shoots change from a vertical position to a more radial one. During this change to a typical spherical shape high levels of the plant hormone jasmonic acid and its precursor 12-oxophytodienoic acid accumulate. In 2003, we determined a 100-fold increase in the levels during the nutational period compared to that four weeks before. Most of the jasmonic acid appeared as (+)-7-iso-jasmonic acid indicating its de novo synthesis. These results are the first proof of the occurrence of jasmonates in mistletoe and suggest a new role of these compounds in nutational movement.

The seasonal changes in levels of jasmonate observed in 2003 were confirmed by analyses for each year of 2003-2006. Under constant conditions in climate chambers we also found high levels of both jasmonic acid and 12-oxophytodienoic acid. Moreover, we could show altered levels of jasmonate during the course of the day. The flexibility of mistletoe in terms of jasmonate levels is also supported by a wound-induced accumulation of jasmonate, a well-known phenomenon for most plants.

Fingrut and Flescher showed that jasmonic acid induces apoptosis and suppresses cell proliferation in various human cancer cells. Prior to 2006 its anti-cancer effect has been shown in more than 15 human cancer cell lines which led to a more public acceptance of the anti-cancer effect of jasmonates. Consequently, our data support a link between antitumour activity of mistletoe and anti-cancer activity of applied jasmonates.

Keywords: Mistletoe; Jasmonates; Chronobiological phenomena; Nutational movement; Anti-tumour remedy

R. Dorka (a,*), O. Miersch (b), C. Wasternack (b), P. Weik (a)

(a) Carl Gustav Carus-Institut, Am Eichhof 30, D-75223 Niefern-Oschelbronn, Germany

(b) Leibniz-Institut fur Pflanzenbiochemie, Weinberg 3, D-06120 Halle/Saale, Germany

*Corresponding author. Tel.: [phone]; fax: [phone].

E-mail address: [e-mail] (R. Dorka).