Plant Physiology 96:245-250 (1991)
© 1991 American Society of Plant Biologists
Environmental and Stress Physiology
Elevated Accumulation of Proline in NaCl-Adapted Tobacco Cells Is Not Due to Altered 1-Pyrroline-5-Carboxylate Reductase 1
P. Christopher LaRosa,
David Rhodes,
Judith C. Rhodes,
Ray A. Bressan and
Laszlo N. Csonka
Department of Horticulture, Purdue University, West Lafayette, Indiana 47907,
Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907
Tobacco (Nicotiana tabacum L. var Wisconsin 38) cells that are adapted to 428 millimolar NaCl accumulate proline mainly due to increased synthesis from glutamate. These cells were used to evaluate the possible role of 1-pyrroline-5-carboxylate reductase in the regulation of proline biosynthesis. No increase in the specific activity of 1-pyrroline-5-carboxylate reductase in crude extracts throughout the growth cycle was observed in NaCl-adapted cells compared to unadapted cells. The enzyme from both cell types was purified extensively. On the basis of affinity for the substrates NADPH, NADH, and 1-pyrroline-5-carboxylate, pH profiles, chromatographic behavior during purification, and electrophoretic mobility of the native enzyme, the activities of the enzyme from the two sources were similar. These data suggest that the NaCl-dependent regulation of proline synthesis in tobacco cells does not involve induction of pyrroline-5-carboxylate isozymes or changes in its kinetic properties.
1 Supported by U.S. Department of Agriculture Research Grant 87-CRCR-12495. Journal Paper No. 12749, Purdue University Agricultural Experiment Station.
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