Role of cytoplasmic inorganic phosphate in light-induced activation of H+-pumps in the plasma membrane and tonoplast of Chara corallina

Abstract

A unique variant strain of Chara corallina, which contains little inorganic phosphate in the vacuole ([Pi]v) was isolated. The level of cytoplasmic inorganic phosphate ([Pi]c) in these cells was the same as that in normal cells. Using these unique cells, we studied the change in [Pi]c and the effect of Pi on the activities of electrogenic H(+)-pumps associated with the plasma membrane and tonoplast. Upon illumination, the plasma membrane of C. corallina became hyperpolarized by 15 mV, the pH of the vacuolar sap decreased by 0.5 unit, and [Pi]c decreased by 30% with a similar time course. The activities of the electrogenic H (+)-pump in the plasma membrane and the ATP and PPi-dependent H(+)-transport in the tonoplast were noncompetitively inhibited by Pi with Ki values of, in the order given, 21.3 mM, 22.1 mM and 37.7 mM. From the kinetics study we calculated that the electrogenic H(+)-pump in the plasma membrane and the ATP and PPi-dependent H(+) transport in the tonoplast were activated by, again in this order, 13%, 13% and 9%, in accordance with the decrease in [Pi]c. We propose that the change in [Pi]c is one of the regulators of photosynthesis-mediated activation of the H(+)-pumps in the plasma membrane and the tonoplast in C. corallina upon illumination.

The Stomata of the Fern Adiantum capillus-veneris Do Not Respond to CO2 in the Dark and Open by Photosynthesis in Guard Cells

“…However, the activation mechanism of the H 1 -ATPase by photosynthetic electron transport in the fern remains unclear. The photosynthesis-induced membrane hyperpolarization by H 1 -ATPase has been reported in green algae Chara (Takeshige et al, 1992) and in aquatic angiosperm Vallisneria leaves (Harada et al, 2002). In Vallisneria, the H 1 -ATPase is activated by a decrease in the K m for ATP through photosynthetic active radiation and is suppressed by DCMU.…”

Photosynthetic control of the plasma membrane H + -ATPase in Vallisneria leaves. II. Presence of putative isogenes and a protein equipped with a C-terminal autoinhibitory domain

“…Because Takeshige et al (1992) reported a lightdependent decrease in the cytoplasmic content of Pi in the internodal cells of Chara corallina, and Sicher and Kremer (1988) reported a similar decrease in the leaves of Hordeum vulgare, a light-dependent retrieval of PM H + -ATPase activity through the C-terminal autoinhibitory domain might occur in V. gigantea. However, in the case of Chara corallina (Takeshige et al 1992), the light-induced membrane hyperpolarization was observed much earlier than the detectable decrease in the cytoplasmic level of Pi. On the other hand, in the samples prepared from the V. gigantea leaves before and after in vivo illumination, we determined the kinetic parameters of the activities of ATP hydrolysis and H + transport in the absence of Pi (Harada et al, in press).…”

“…These results indicate that, in the presence of Pi, the light-dependent changes in the K m may occur at higher concentration ranges of ATP. Consequently, although the cytoplasmic concentration of ATP in plant cells supposedly ranges from submillimolar to a few millimolar (Keifer and Spanswick 1979;Kikuyama et al 1979), a photosynthesis-dependent decrease in the K m for ATP might accelerate the activity of the PM H + -ATPase, because the PM H + -ATPase is supposed to be constitutively exposed to cytoplasmic Pi in vivo at approximately 10-15 mM (Takeshige et al 1992). Separately, the level of ATP in a very limited space contiguous to the PM, which should have critical effects on the activity of the PM H + -ATPase ), remains to be determined.…”

“…Unless otherwise noted, PM vesicles were isolated from leaves grown under white light on a daily cycle. As the source of exogenous Pi, we used a solution of KH 2 PO 4 , the pH of which was adjusted to pH 7.0 with KOH (Takeshige et al 1992).…”

“…We also examined how many isogenes for the PM H + -ATPase were expressed in the leaves. We further examined the effects of inorganic phosphate (Pi), whose concentration in the cytoplasm is 10-15 mM (Takeshige et al 1992), on the H + -transporting activity in the isolated PM vesicles. Based on the inhibitory effects of Pi on the H + -transporting activity in PM vesicles isolated from the leaves before and after red-light irradiation, we discuss possible modes for a photosynthesis-dependent modulation of the activity of the PM H + -ATPase.…”