CHANGES IN PROTEASOME LEVELS IN SPINACH (SPINACIA-OLERACEA) SEEDS DURING IMBIBITION AND GERMINATION

Proteasomes are the major cytosolic protease complexes responsible for energy-dependent and extra-lysosomal proteolysis, Ubiquitinated prote ins are degraded by the 26S proteasome which is composed of a 20S prot easome and two regulatory complexes, Changes in the 20S and 26S protea some activity levels and protein abundance in spinach seeds during imb ibition and germination were examined by using glycerol density gradie nt centrifugation, The 26S proteasome activity level decreased transie ntly during imbibition, reached a minimum one day after starting imbib ition, and then increased again, During the period of minimal accumula tion, the protein being detected with an anti-26S proteasome antibody shifted to a lower sedimentation coefficient fraction, In contrast, th e 20S proteasome activity level increased during imbibition, and remai ned high for two days, The change in the 20S proteasome level correspo nded to the change in the 20S proteasome activity level.