Expression of delta(1)-pyrroline-5-carboxylate dehydrogenase and proline/arginine homeostasis in Solanum tuberosum

Polyclonal antibodies raised in mouse against purified potato delta(1)-pyrr oline-5-carboxylate dehydrogenase (P5C-DH, EC 1.5.1.12), which catalyses th e fast step in the catabolism of both proline and arginine, were used to in vestigate the expression of this enzyme. Distribution of P5C-DH in potato ( Solanum tuberosum L. cv. Desiree) organs was studied at different stages du ring plant development. Variations in enzyme level were determined in axeni cally grown plantlets following the addition of exogenous proline, and in c ell suspension cultures under hyperosmotic stress and after its relief. Fre e proline and arginine levels were also quantified, and compared to those o f the enzyme. Results were consistent with a developmental, but not with an environmental, control of P5C-DH expression. The possible involvement of s pecific isozymes in proline and arginine oxidation is discussed.