THE MECHANISM AND REGULATION OF PROLINE ACCUMULATION IN SUSPENSION CELL-CULTURES OF THE HALOPHYTIC GRASS DISTICHLIS-SPICATA L

Proline accumulation in the halophyte Distichlis spicata L. occured rapidly following initiation of NaCl-induced stress and stabilized at an elevated level within 48 h of exposure to NaCl. Accumulation of proline was inhibited by cycloheximide but not by actinomycin D, suggesting that mRNA translation but not mRNA transcription may be necessary prior to production of proline in stressed cells. Protoplasts and vacuoles were isolated to examine partitioning of proline between protoplast and vacuole. Significant amounts of free proline leaked from the protoplasts or cells into the enzyme solution during isolation. Numerous vacuoles were released from a single protoplast during protoplast lysis. The isolated vacuoles contained a minor fraction of the cellular proline.