Cytoplasmic Acidification and Secondary Metabolite Production in Different Plant Cell Suspensions (A Comparative Study)

Abstract

In this study, a correlation is described between low cytoplasmic pH, measured with the fluorescent probes 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (acetoxymethyl ester) and bis-[3-propyl-5-oxoisoxazol-4-yl]pentamethine oxonol, and the production of secondary metabolites for several plant cell-suspension systems. Anthraquinone production in Morinda citrifolia suspensions is negligible in the presence of 2,4-dichlorophenoxyacetic acid (2,4-D), whereas with naphthalene acetic acid (NAA) a significant accumulation is realized. NAA-grown cells showed a lower cytoplasmic pH than did 2,4-D-grown cells. Addition of 2,4-D or parachlorophenoxy acetic acid to NAA-grown cells resulted in an inhibition of anthraquinone production and an increase of the cytoplasmic pH, whereas addition of parachlorophenyl acetic acid had no effect on either parameter. lignin produdion in Petunia hybrida cells could be induced by subculturing them in a medium without iron. These cells showed a lower cytoplasmic pH than control cells. Addition of Fe3+ led to a decreased lignin content and an increased cytoplasmic pH. Two cell lines of Linum flavum showed a different level of coniferin and lignin concentration in their cells. Cells that accumulated coniferin and lignin had a lower cytoplasmic pH than cells that did not accumulate these secondary metabolites. Apparently, in different species and after different kinds of treatment there is a correlation between acidification of the cytoplasm and the production of different secondary metabolites. The possible role of this acidification in secondary metabolite production i s discussed.Some plant tissues are able to produce substantial amounts of secondary metabolites. However, the production of these compounds in plant cell and tissue cultures is generally low. A number of treatments have been described that lead to an increased production; these treatments often stimulate the defense response in the cell (Scheel and Parker, 1990).In a previous paper (Hagendoom et al., 1991a), we ana- 723lyzed the effect of elicitors on the plasma membrane of Petunia hybrida cell suspensions. It appeared that changes in the activity of the plasma membrane ATPase, and subsequently of ApH, were sufficient to increase PAL activity and product formation in these cells. This conclusion was based on two different experimental approaches. First, we tested a number of plasma membrane ATPase inhibitors and ionophores that specifically influence ApH, A*, or both for their ability to activate secondary metabolism. Second, we directly showed changes in cytoplasmic pH upon activation of a secondary metabolic pathway with the aid of the fluorescent probe oxonol VI.In this paper we show that this relation between low cytoplasmic pH and secondary metabolite production is not limited to P. hybrida and the products of the PPP but can also be observed in different model systems. We investigated the production of secondary metabolites by cell suspensions derived from three plant species belonging to three different fa...

Growth, secondary metabolite production and antioxidant enzyme response of Morinda citrifolia adventitious root as affected by auxin and cytokinin

“…For example, in the case of the M. citrifolia cell culture, high concentrations of NAA reduced the production of anthraquinone (Zenk et al 1975). On the other hand, the production of anthraquinone was induced by NAA and inhibited by 2,4-D in the same species (Hagendoorn et al 1994). They observed that, in cultures treated with high concentrations of NAA, concomitant alkalization occurred in the cytoplasm, leading to cell death and a subsequent drop in metabolite accumulation.…”

Cytoplasmic acidification as an early phosphorylation-dependent response of tobacco cells to elicitors

“…According to Hagendoorn et al (1994), cytoplasmic acidification does not constitute a secondary messenger, but might be a part of the metabolic shift responsible for the production of secondary metabolites following the treatment with elicitors.…”

Increase of defense gene transcripts by cytoplasmic acidification in tobacco cell suspensions

“…In cultured parsley cells, the cytoplasmic pH decreased upon treatment with a Phytophthora megasperma preparation and the pH shift has been correlated with activation of a hydroxylase acting in the synthesis of lignin (Kneusel et al 1989). Using¯uorescent probes, a correlation between secondary metabolite production and a low cytoplasmic pH was observed for three plant species (Hagendoorn et al 1994). Recently, a technique based on the distribution of [ 14 C]benzoic acid between the intracellular and extracellular compartments was used to explore elicitor-induced pH changes in a variety of conditions.…”