Cyclitol accumulation in suspended cells and intact plants of Cicer arietinum L.

Intact plants and cells (photoautotrophic, photomixotrophic, heterotrophic) in suspension culture of Cicer arietinum L. were compared for their ability to synthesize and accumulate O-methyl-inositols. In intact plants (leaves, shoot axis, roots), pinitol (1D-3-O-methyl-chiro-inositol) was the major cyclitol of the polyol fraction and it was accumulated in response to drought stress. Withholding water from the plants for 14 days caused an increase in pinitol from 5 to 195 mmol kg-1 dry matter in the leaves, from 9 to 67 mmol kg-1 dry matter in the shoot axis and from 5 to 22 mmol kg-1 dry matter in the roots, which was far beyond the levels in controls of the same age. In contrast to the intact plants pinitol was not detectable in most of the suspension cultured cells. It was only present in small amounts (<5 mmol kg-1 dry matter) in photoautotrophic cells when cells were stressed with either 100 mol m-3 NaCl or 200 mol m-3 sorbitol. The precursor of pinitol, ononitol (1D-4-O-methyl-myo-inositol), appeared in traces under control conditions in photomixotrophic cells, but was accumulated up to 27 mmol kg-1 dry matter under salinity conditions (100 mol m-3 NaCl). No methylated cyclitol was detectable in heterotrophic cells. However, when photoautotrophic cells were reverted to heterotrophic conditions they maintained the ability to synthesize ononitol for more than 6 months. The presented data provide evidence that O-methyl-inositol synthesis can be induced on the cellular level. Photosynthetic activity of the cells is not a necessary prerequisite for accumulation of methylated polyols.