Tetracyclines, verapamil and nifedipine induce callose deposition at specific cell sites in Riella helicophylla

Abstract

The Ca(2+) indicator 7-chlorotetracycline has been shown to bind to a pore complex on both outer surfaces of all non-meristematic cells in the unistratose thallus of Riella ('chlorotetracycline-binding surface region'=CSR; Grotha, 1983, Planta 158, 473-481). Prolonged treatment of the thallus with 7-chlorotetracycline, 5-hydroxytetracycline, verapamil and desmethoxyverapamil induces the deposition of callose at the same region. The influence of various treatments on verapamil-induced CSR-callose was measured in situ by microfluorometry of aniline-blue-stained material. Callose deposition is maximal at 10(-4)M verapamil or 5·10(-5)M desmethoxyverapamil with 2·10(-4)M Ca(2+) or Mg(2+) in the medium. The reaction is completely inhibited at pH 5.5 and is optimal between pH 6.5 and 7.5. The production of CSR-callose is absolutely light-dependent with callose being first visible after 30 min of light. La(3+), ethylene glycol-bis(β-aminoethylether)-N,N,N',N'-tetraacetic acid and amiprophosmethyl, antagonists of Ca(2+) functions, and 2-deoxy-D-glucose suppress the verapamil induction of CSR-callose. Furthermore the ionophores A 23187, valinomycin and monensin effectively block the reaction. The deposition of CSR-callose is diminished at increasing external osmolarity and is abolished at osmotic values that stimulate plasmolysis-callose. Wounding causes the formation of wound-callose but inhibits the induction of CSR-callose in cells of the wound edge. Nifedipine increases or prolongs callose synthesis in cell plates. The Ca(2+)-channel blocker diltiazem is completely ineffective. It is suggested as a working hypothesis that verapamil-induced CSR-callose synthesis is caused by a local change in membrane permeability, possibly as a consequence of the opening of Ca(2+) channels being involved in Golgi-vesicle mediated exocytosis (A. Kramer and H. Lehmann, 1986, Ber. Dtsch. Bot. Ges. 99, 111-121).

Cytokinin stimulates dihydropyridine-sensitive calcium uptake in moss protoplasts.

“…In moss protoplasts, the half-maximal effect of nifedipine is observed at 500 nM, indicating that Ca2+ influx inhibition by nifedipine is pharmacologically linked to inhibition of bud formation; in intact cells, bud formation was reduced >50% by 10 ,uM nifedipine (13). While there is growing evidence for an effect of DHPs in a number of physiological processes in plants (29)(30)(31), there has not been consistent evidence for DHPsensitive Ca2+ transport and DHPs have shown little effect at the membrane level (32)(33)(34)(35). The results presented here demonstrate DHP-sensitive Ca2+ influx into single cells in a system previously shown to respond to these compounds at the whole plant level.…”

1,4-Dihydropyridine Binding Sites in Moss Plasma Membranes

“…Cytoplasmic calcium levels have been shown to increase in response to a variety of stimuli including light (5,6) and hormones (7,8), and small fluctuations in cellular calcium may modulate processes as diverse as secretory activity in the barley aleurone (7), pollen tube growth (9), and phase transition in mitosis (10). Studies examining the effect of calcium channel inhibitors on physiological processes (11)(12)(13)(14) have suggested a role for calcium channels in stimulus-induced increases in cytoplasmic calcium levels; however, little is known about the biochemical or molecular properties of these transport systems.…”

Effects of nifedipine, verapamil, and diltiazem on tip growth inFunaria hygrometrica

“…Our results are in apparent contrast to these findings: the Ca 2 + antagonist verapamil is able to induce the formation of polarly distributed callose deposits in tip cells of the moss Funaria hygrometrica. An analogous phenomenon is reported in the liverwort Riella helicophylla (Grotha 1986). Here, callose deposition was induced by tetracyclines or verapamil and was restricted to specific cell sites, actively engaged in exocytosis.…”

“…Nifedipine prolonged the formation of cell-plate callose in Riella. The author concludes "that different Ca 2 § channels may be involved in callose synthesis at different cell sites" (Grotha 1986). Nevertheless, it seems strange to assume that a substance presumed from animal systems to be a Ca 2 § antagonist can induce an apparently Ca a +-dependent process.…”