No abstract

Cell suspension cultures of parsley (Petroselinum hortense) grown in synthetic medium take up most of the inorganic phosphate supplied with the medium within the initial 5 days after transfer. Nuclear magnetic resonance spectra of intact parsley cells from this growth stage revealed that approximately half of the phosphate was located within the vacuoles, whereas after 7 days of growth phosphate content of the vacuoles was relatively low. At both times, addition of an elicitor preparation from Alternaria carthami, which is not toxic to the cells, led to a temporary increase of vacuolar phosphate at the expense of cytoplasmic phosphate, even when excess phosphate was added to the medium. The rapid decrease of cytoplasmic phosphate might play a role in the redirection of phenylpropanoid metabolism reported for elicitor-treated parsley cells.

The phospholipids of cultured parsley and soybean cells were labelled with myo-[2-3H]inositol, [2-3H]glycerol or [32P]orthophosphate. By one-and two-dimensional chromatographic comparison of the labelled phospholipids with reference substances, the presence of 1-(3-sn-phosphatidyl)-ᴅ-myo-inositol 4-phosphate and 1-(3-sn-phosphatidyl)-ᴅ-myo-inositol 4,5-bisphosphate was demonstrated in these cultures. These results were corroborated by analysis of the deacylation products. Cells were labelled with either myo-[2-3H]inositol, [2-3H]glycerol or [32P]orthophosphate and subsequently challenged with elicitor for various lengths of time. Radioactivity in individual phosphoinositides from these cells was determined. No significant influence of elicitor-challenge of either soybean or parsley cells on incorporation of 3H or 32P into polyphospho­inositides was found between 0.5 and 20 min after elicitor addition.

Elicitor preparations derived from cell walls of phytopathogenic Alternaria spp. rapidly inhibited uptake of both inorganic phosphate and amino acids by cultured parsley cells. The inhibition of phosphate uptake was completely reversed if the elicitor was removed within a time period of approximately 20 min following its addition to the cell cultures. Cells which had been exposed to the elicitor for more than 20 min prior to washing, however, exhibited an increasingly reduced rate of phosphate uptake as compared to non-induced controls. Maximal inhibition of phosphate uptake (about 30 to 40% of the controls) required 40 min or more of elicitor treatment. These results confirm that a minimal time of exposure to elicitor of about 20 min is necessary to induce lasting effects in parsley cells. Moreover, the initial inhibition of amino acid uptake into the parsley cells suggests that the elicitor rapidly decharged the plasmalemma potential of the cells.