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Transport of 1‐aminocyclopropane‐1‐carboxylic acid into isolated maize mesophyll vacuoles
Author(s) -
Saftner Robert A.,
Martin Melinda N.
Publication year - 1993
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1993.tb02504.x
Subject(s) - vacuole , 1 aminocyclopropane 1 carboxylic acid , electrochemical gradient , chemistry , valinomycin , atpase , ethylene , proton transport , gramicidin , biophysics , biochemistry , membrane potential , membrane , enzyme , biology , cytoplasm , catalysis
Intracellular transport of the ethylene precursor, I‐aminocyclopropane‐1‐carboxylic acid (ACC) can change the ACC concentration in cell compartments and impact ethylene biosynthesis. Transport of ACC into isolated maize ( Zea mays L.) mesophyll vacuoles was studied by silicon layer flotation filtering. The transport of ACC across the tonoplast was stimulated 2. 4‐ to 8. 1‐fold by 5 m M MgATP, showed saturation kinetics with an apparent K m for ACC of 20 μ M , and was optimal at 25°C. Transport of ACC was sensitive to the pH of the medium, falling as external pH rose. Effectors known to inhibit proton‐translocating ATPases (N, N‐dicyclohexylcarbodiimide) and to collapse the electrical (thiocyanate, valinomycin) and chemical (carbonylcyanide m ‐chlorophenylhydrazone, gramicidin) potential gradients for protons across the tonoplast all reduced ACC transport. The nonhydrolyzable MgATP analog. Mg adenylyl‐imidodiphosphate, stimulated ACC transport as effectively as MgATP. Other nucleotides (MgADP, MgCTP, MgUTP, MgGTP) and MgPP i had little or no effect. These results suggest that ACC uptake into isolated maize mesophyll vacuoles is carrier mediated, is dependent upon an electrochemical potential gradient for protons and is specifically regulated, but not necessarily energized, by MgATP