ANAPLEROTIC RESPONSES OF ARABIDOPSIS THALIANA CELL CULTURES TO ALTERED GRAVITATIONAL FIELD STRENGTHS

摘要

Anaplerosis is a metabolic pathway which becomes important when plant cells are exposed to stress. Its main function is to supply carbon skeletons for the de novo synthesis of amino acids and, finally, proteins. As we have indications that changes in gravitational field strengths lead to a general stress response in plant cells (Martzivanou and Hampp PHYSIOL. PLANT., Vol 118, 221-231, 2003) we used both suspensions of cell cultures and callus cultures of Arabidopsis thaliana (cv. Columbia) to investigate activation state, amount of specific protein, and transcript levels of the key enzyme of plant anaplerosis, phosphoeno/pyruvate carboxylase (PEPC). In addition, relevant metabolite pools and labelling patterns after feeding of (~(14)C)glucose were determined. For this purpose, cells were exposed to altered g-forces due to clinorotation (random positioning machine), centrifugation (1 to 10g), and in the course of a sounding rocket flight (TEXUS 39; down'to 10~(-4)g). Hyper-g treatment resulted in a transient increase of PEPC activity after a 1h-exposure to g-forces between 5 and 10. This was due to de novo synthesis of the enzyme protein as both enzyme-specific protein and the respective transcript increased.