Trigonelline accumulation in salt-stressed legumes and the role of other osmoregulators as cell cycle control agents

Plants, when exposed to excess salt, accumulate osmoregulators such as glycine betaine, proline and trigonelline to prevent water loss. Alfalfa (Medicago sativa) shows a five-fold proline increase and a two-fold trigonelline increase after salt-stress. Trigonelline also has a second function as a cell cycle regulator during the early growth of many legume root meristems. In this study, greenhouse grown soybeans (Glycine max) were exposed to salt-stress and levels (mu g g(-1), dry wt) of trigonelline were determined in leaf samples until senescence. Significant trigonelline increases occurred, beginning several weeks after salt exposure. Further experiments determined if other known osmoregulators (proline, glycine betaine) could affect the cell cycle parameters in cultured root meristems of peas (Pisum sativum), in a manner similar to trigonelline. Mitotic values remained near 4% of controls. At concentrations of 10(-4)-10(-7) M trigonelline, an accumulation of G2 nuclei occurred, whereas proline was ineffective and glycine betaine only slightly effective in promoting G2 nuclei accumulation. These results demonstrate that the cell cycle effects of the trigonelline molecule are indeed specific and that its role as an osmoregulator in salt-stressed legumes is strengthened. Copyright (C) 1997 Elsevier Science Ltd.