Proline metabolism and NAD kinase activity in greenbean plants subjected to cold-shock.

The aim of the present work was to examine the relationship between proline metabolism and NAD kinase activity in greenbeans submitted to cold-shock. For this, 15-day-old greenbean plants were subjected to a temperature of 4 degrees C (cold shock) for 180 min. Our results indicate that the plants showed foliar accumulation of proline, with the enzymes ornithine-delta-aminotransferase (OAT) and proline dehydrogenase (PDH) appearing as determinant in this accumulation under cold-shock. Also, we found a close relationship between the Ca(2+)-CaM-dependent NAD kinase activity and proline metabolism, suggesting that the adaptive responses or acclimation of plants to cold stress are preceded by increased [Ca(2+)](cyt).