Changes of some properties of the plasma membrane-enriched fraction of barley roots related to aluminum stress: Membrane-associated ATPase, aluminum and calcium

Matsumoto, H.; Yamamoto, Y.; Kasai, M.

Soil Science and Plant Nutrition 38(3): 411-419


ISSN/ISBN: 0038-0768
DOI: 10.1080/00380768.1992.10415073
Accession: 008287985

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A microsomal membrane fraction was prepared from barley (Hordeum vulgare) roots which were treated with and without 1 mM AlCl-3. Plasma membrane was dominant in the fraction based on the inhibitor experiment of ATPase activity. ATPase activity of the microsomal membrane fraction decreased after treatment of roots with aluminum. The microsomal membrane fraction was fractionated on a continuous density gradient of sucrose, and the amount of Ca-2+ and aluminum associated with the membrane was investigated. The ATPase activity of roots treated with 1 mol m-3 AlCl-3 for 5d decreased to 55.3% of that of the control sample. The amount of Ca-2+ associated with the membrane of the Al-treated sample was approximately half as large as that of the control, while substantial binding of A1 to the membrane was observed in the sample prepared from the aluminum-treated roots. The K-m values for ATP of the fractionated ATPase was 0.45 mol m-3 in both the aluminum-treated and control sample while V-max was smaller in the Al-treated sample. Futhermore, the optimum pH was different between the ATPase prepared from the control and that from the albuminum-treated roots. Activation of ATPase with asolectin, a soybean phospholipid, was revealed in the sample prepared from the A1-treated roots but not in the control one. These results suggest that the structure of the plasma membrane in barley roots was impaired by aluminum stress.