Polyamine metabolism in nodules and roots of soybean plants under cadmium stress”.

BALESTRASSE KB, BENAVIDES MP AND TOMARO ML

Bariloche, Río Negro. Argentina.

Congreso; Annual Meeting SAIB, Protein Symposium. XXXIX Reunión Anual Sociedad Argentina de Investigación Bioquímica y Biología Molecular. Bariloche, Río Negro. Argentina.; 2003

SAIB

Polyamines (Pas) have been reported to be involved in several kinds of abiotic stresses in plants. However, there is no information regarding putrescine (Put), spermidine (Spd) and spermine (Spm) metabolism in soybean plants under cadmium stress. Both cadmium treatments, 50 µM and 200 µM, modified Pas metabolism in soybean, by increasing Put and Spm in nodules, and Put and Spd in roots of treated plants. In roots and nodules, Put formation could be attributed to the activity of both biosynthetic enzymes, arginine decarboxylase (ADC), which was 7 times higher than ODC in controls and 50 µM Cd-treated nodules, and ornithine decarboxylase (ODC), which was responsible for Put formation in nodules under 200 µM cadmium, where ADC activity was almost undetectable. A clear increase in Spm and Spd content were observed in nodules and roots respectively, after day 6 under the metal treatments and this increase was concurrent with a drop in ethylene formation. In nodules under cadmium stress, Spm was higher than controls, and so was S-adenosylmethionine decarboxylase (SAMDC) activity, but the highest Spm level was observed after SAMDC began to decline. Our results demonstrate that polyamine metabolism is altered by cadmium stress in roots and nodules of soybean plants. In contrast to previous reports, neither Put accumulation correlated with toxicity symptons (nodules and roots of 50 µM cadmium treated plants) nor ethylene decline or Spm and Spd increase in nodules and roots avoided the onset of senescence in plants treated with 200 µM cadmium.