ISSN:
1432-2048
Keywords:
Key words: Catharanthus
;
Chromate
;
4
;
4-Diisothio cyanostilbene-2
;
2′-Disulfonic acid
;
Phosphate transport
;
Tonoplast
;
Vacuole
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract. Transport of inorganic orthophosphate (Pi) across the tonoplast membrane was studied using intact vacuoles isolated from suspension-cultured cells of Catharanthus roseus. Orthophosphate uptake was strongly stimulated in the presence of Mg-ATP and Mg-pyrophosphate and inhibited by bafilomycin and concanamycin which are potent inhibitors of the vacuolar H+-ATPase. These results indicated that the build-up of an electrochemical gradient by the H+ pumps was essential for the uptake of Pi. Potassium thiocyanate, which dissipates the membrane potential across the tonoplast, strongly inhibited the Mg-ATP-stimulated uptake of Pi, while only a weak inhibition was observed in the presence of NH4Cl, which dissipates the pH gradient. These results indicate that, as observed for other anions like malate or chloride, the electrical component is the driving force of Pi uptake, whereas the ΔpH plays only a minor role. Possible competitive inhibitors of Pi, MoO2− 4, VO3− 4 and CrO2− 4 were tested. Among them, CrO2− 4 strongly inhibited Pi uptake into the vacuoles. Various inhibitors of anion transport were also tested. Only 4,4-diisothiocyanostilbene-2,2′-disulfonic acid strongly inhibited Pi uptake into the vacuoles. The function of the vacuolar Pi transporters for cytoplasmic Pi homeostasis is discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/s004250000297
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