Anpassung der Plamalemma-H⁺-ATPase von Proteoidwurzeln der Weißlupine an Phosphatmangel

Abstract

White lupin (Lupinus albus L) is able to adapt to phosphorus deficiency by producing proteoid roots, which release a large amount of organic acids, phosphatases, and phenolic substances to mobilize sparingly soluble soil phosphate in the rhi-zosphere. Previously we showed that rhizosphere acidification by proteoid roots is related to the higher activity of plasma membrane p⁺-ATPase. In the present study we focused on the mechanisms which are responsible for the increase in the activity of plasma membrane H⁺-ATPase of active proteoid roots. Plasma membranes were isolated from proteoid roots and lateral roots from P-deficient and P-sufficient plants. The plasma membrane H⁺-ATPase enzyme concentration was determined by means of Western analysis using a specific antibody for plant plasma membrane H⁺-ATPase. In comparison with lateral roots, the plasma membrane H⁺-ATPase enzyme concentration was four times higher for active proteoid roots. In addition, the ATPase hydrolytic activity in plasma membrane of active proteoid roots showed a more acidic pH optimum, lower affinity to the substrate and lower vanadate sensitivity. Our data indicates that both quantitative and qualitative modifications of plasma membrane H⁺-ATPase contribute to the adaptation of active proteoid roots from P-deficient white lupin to P deficiency.