Changes in ethanol, lactate and malate content in Acer pseudoplatanus cells: effects of fusicoccin and O₂ availability

Abstract

Cerana, R., Patti, V. and Lado, P. 1989. Changes in ethanol, lactate and malate content in Acer pseudoplatanus cells: effects of fusicoccin and O2 availability. Changes in the contents of ethanol, lactate and malate were determined at different activities of the plasma membrane H* pump [in the presence and absence of fusicoccin (FC)] and at different O2 availability in cultured cells of Acer pseudoplatanush. FC induced acidification of the medium under all tested conditions of O, availability. At low Oi concentrations both ethanolic and lactic fermentations occurred, and FC markedly stimulated lactate production but had no effect on ethanol production. There was also a small, stimulating effect of FC on malate production. At high O2 concentrations no ethanol production was observed and lactate production was reduced. Under these conditions the stimulating effect of FC on lactate production decreased, while that on malate production increased. FC-induced synthesis of lactate and malate is interpreted as depending on the activation of lactate dehydrogenase (EC 1.1.1.27) and phosphoenoipyruvate carboxylase (EC 4.1.1.31) (alkaline pH optima), respectively, due to the alkalinization of the cytoplasmic pH resulting from the stimulation of the H* pump by FC. These results suggest that the balance between the two pH stat systems depends on the availability of Oi.

Conditioning of the culture medium by suspension cells and formation of somatic proembryo in Araucaria angustifolia (coniferae)

“…4), reaching its highest value (5.6) after 30 d. Control treatments without cells showed a slightly decreased pH over the same period. Acidification of culture medium is often observed in plant cell cultures (Singha et al, 1987;Cerana et al, 1989;Sakano et al, 1997) and relates to nitrogen metabolism: the preferential assimilation of NH 4 + over NH 3 Ϫ results in metabolic production and extrusion of H + to the medium (Raven, 1988). Another aspect of medium acidification is the unbalanced uptake of ions during salt absorption.…”

Suitability of Arabidopsis for studies on intracellular pH regulation: correlation between H+ pump activity, cytosolic pH and malate level in wild‐type and in a mutant partially insensitive to fusicoccin

“…Taken as a whole, the data reported above indicate that the characteristics of Arabidopsis thaliana seedlings, as regards the parameters so far investigated, do not differ from those of a large variety of plants used for transport studies, and that the physiological responses to different effectors of the H"^ pump activity can be measured at least as well. In addition, two peculiar features of Arabidopsis seedlings indicate this material as particularly suitable for studies on intracellular pH regulation: the low basal malate level, and the low basal cell sap buffer capacity, which are both about 30% or less of those reported for other materials (Gabella & Pilet 1980;Kurkdjian et al 1985;Marre et al 1987;Trockner & Marre 1988;Cerana, Patti & Lado 1989). In fact, the low basal malate content allows us to detect and emphasize even small responses of the malate system to changes in cytosolic pH, and the determination of this parameter can be utilized as a further alternative method to evaluate satisfactorily either the direction or the entity of the changes in cytosolic pH.…”

Low O2-induced changes in pH and energy charge in pear fruit tissue

“…The cellular functions that take place in the cytosol are optimal at a pH near neutral and the cytosolic pH is usually found to be around 7.4. To maintain cytoplasmic pH, metabolic processes consume or produce protons and H+-pumps operate in the plasmalemma and in the tonoplast (Torimitsu et al, 1984;Cerana et al, 1989;Kurkdjian and Guern, 1989). These pumps use large amounts of energy to maintain proton gradients and counteract leakage through the plasmalemma or tonoplast.…”