Study on aluminium resistance in relation to organic-acid anion exudation from roots of PEPC transgenic rice plants

Abstract

Phosphoenolpyruvate carboxylase (PEPC) transgenic rice plants, to which a whole gene of PEPC of maize was introduced, were tested for Al resistance. When the intact gene of maize PEPC was introduced into the C3 crop rice, PEPC activity in leaves of some transgenic rice plants were two to three times higher than those in maize. 14C distribution to organic acids at 0 minute after 5 minutes 14CO2 assimilation was almost two times higher in transgenic rice plant than in control rice plant. Relative growth of control rice plant decreased with increasing Al application. However, that of transgenic rice plant increased with increase of Al application. Organic acid-anion exudation from roots of control plant remained regardless of Al application. However, Al treatment enhanced particularly oxalate exudation from roots of the transgenic plants. These results are in agreement with the better growth of the transgenic compared to the control plants in presence of Al. From these results we conclude that the higher Al resistance of the PEPC transgenic plants is due to enhanced synthesis of organic acids in the leaves, transport to the roots and exudation from the roots.