Heat shock-induced cadaverine accumulation and translocation throughout the plant

To test the possibility of heat shock (HS)-induced cadaverine accumulation and translocation throughout the plant, the titres of free polyamines in different plant organs, xylem and phloem exudates of the common ice plant (Mesembryanthemum crystallinum L.) were studied. Cadaverine level was relatively low in young leaves and apexes, while this diamine occurred in roots and stems at higher concentrations (20-29 nmol g-1 FW). The level of spermidine (60-300 nmol g-1 FW) in plants grown under normal conditions (23-25 °C, 55% RH, 14 h photoperiod) was 10-fold higher than the levels of all other polyamines (6-25 nmol g-1 FW). The plants responded to HS with a change in polyamine balance, as well as with a fast and transient increase in ethylene evolution. Local heating of plant aerial parts (47 °C, 2 h, 100% RH) primarily induced the accumulation of cadaverine and, to a lesser extent, putrescine and spermidine in roots and an increase in cadaverine concentration in the phloem exudate. The HS treatment of the root system resulted in accumulation of cadaverine in plant stems and in the xylem exudate. In contrast, spermine was not able for the long distance transport and stress induced accumulation. Exposure of detached leaves to exogenous ethylene (1-10 μ1 1-1, 4 h) was accompanied by accumulation of cadaverine. Arabidopsis wild type (Col-0) plants contained cadaverine in leaves and roots. In contrast, this diamine was not found in roots of ethylene- insensitive mutant strain (ein4) and accumulated only under HS treatment (45 °C, 1 h). These findings demonstrate ethylene dependent inter-organ translocation of cadaverine, as well as the possible involvement of ethylene in regulation of cadaverine level in plants under stress. © 2001 Elsevier Science Ireland Ltd. All rights reserved