Expression of peroxidases during seedling growth in Ebenus cretica L. as affected by light and temperature treatments

Peroxidase (POD) activity and isoform patterns were investigated during seedling growth (up to 20 days) of Ebenus cretica L. Seeds germinated to approx. 100% after a 24-h imbibition. Seedling growth proceeded smoothly, in both light and dark conditions. No seedling growth was noticed at 4 degrees C. A positive effect of light and increasing temperature (4, 10, 16, 22 and 28 degrees C) on seedlings growth, lignin content and POD activity was observed. Lignin content was 2.5 times higher in seedlings grown under light than in seedlings grown under darkness. Seedlings' POD activity was higher in acid pH (5.5) in comparison to neutral pH (7.0). These activities were higher in seedlings grown under darkness than in those grown under light; since additional POD isoforms were expressed in dark conditions. The increase in POD activity was accompanied with the appearance of new POD isoforms correlated with the growth of the seedlings. Four soluble anionic POD isoforms (named A(1), A(2), A(3) and A(4)) and three soluble cationic POD isoforms (named C-1, C-2 and C-3) were displayed depending on the treatment and the course of growth. POD isoforms were detected in gel after PAGE. The fast migrating (A(4)) isoform, which appeared in the dark-grown seedlings as well as on day 20 at 28 degrees C in the temperature treatment, was separated by DEAE-Sepharose column chromatography. A slow migrating C-1 isoform slightly appeared in both 4 and 10 degrees C temperature treatments and could be related to the low temperature treatments, while A(1), A(2), A(3) and C-2 to the growth stage of seedlings. The expression of seven POD isoforms during seedling growth seems to be related to different developmental events of growth and could be used as useful biochemical markers in the analysis of metabolic regulation in seedling growth of Ebenus cretica.