DEVELOPMENT OF AN ELISA FOR ESTIMATION OF THE COPPER NUTRITIONAL-STATUS OF WHEAT AND COTTON

Studies were carried out with hydroponically grown wheat and cotton to develop the Cu-requiring protein phenolase as a biomarker of Cu nutri ent status. Isozymes of phenolase whose levels were reduced by Cu defi ciency were identified by Western blots. A competitive enzyme-linked, immunosorbent assay (ELISA) was developed that could detect as little as 25 ng of phenolase. The ELISA revealed that Cu-sufficient cotton le aves had about 4-fold more phenolase antigen than did Cu-sufficient wh eat leaves. In both species, the level of phenolase was reduced by 2- to 5-fold in leaves of Cu-deficient plants. Because the immunoassay fo r phenolase protein is rapid, inexpensive, and can be carried out with small amounts of leaf material, it has potential as a tool for assess ment of the Cu status of crop plants.