Isolation of plasma membranes from mung bean hypocotyl sections by two-phase partitioning: suitability of the technique for ageing tissues

Abstract

1994. Isolation of plasma membranes from mung bean hypocotyl sections by two-phase partitioning: suitability of the technique for ageing tissues. -Physiol. Plant. 90: 671-678.This paper discusses the application of a particular two-phase partitioning system to the isolation of plasma membranes from heterogeneous starting material, differing in physiological age. Plasma membranes were isolated from hypocotyl segments of mung beans (Vigna radiata L. Wilczek) on four successive days in order to examine the variation caused by ageing of the seedling. Additionally, the segments were cut at different positions of the hypocotyl to measure variation cau.sed by position-related ageing. To assess purity and degree of contamination of the piasma membraneenriched preparations, a series of membrane enzyme markers were screened for all isolated fractions. Glucan synthetase II activities were etiriched in the plasma membrane fractions, but enrichment and recovery became less pronounced with increasing age. Plasma membrane ATPase activity affected by VO^, Ca-* and K* was similar in all segments throughout the time-course of the experiment (4 days). However, control ATPa.se activity varied with segment origin: the physiologically oldest segments showed only 75% activity compared to the youngest ones. K^ and Vm,, values indicated a smaller proportion of active enzyme but higher substrate affinity as the age of the segments increased. Contamination by intracellular membranes was minimal and unrelated to tissue age.

Purification of plasma membranes from dry maize embryos

“…agglutinability (aleurone layers. Walker et al 1993) and ageing (etiolated hypocotyls, Stallaert et al 1994). Here, we describe a procedure that allows the isolation of plasma membranes from dry maize embryos.…”

Oxidative Stress Results in Increased Sinks for Metabolic Energy during Aging and Sprouting of Potato Seed-Tubers

“…Topophytic effects on vanadate sensitivity have also been documented. For example, the ATPase activity in PMs isolated from the basal portions of mung bean hypocotyls was relatively insensitive to vanadate when compared with that isolated from the remaining hypocotyl tissue (Stallaert et al, 1994). Venken et al (1991) showed that the degree of sensitivity of the PM ATPase to vanadate changes during aging and senescence of oat leaves.…”

“…Even after contamination by non-PM-derived activity was accounted for, inhibition of PM ATPase by vanadate did not increase beyond 40% for the microsomal and UP vesicles (Table 11). Since PM ATPase sensitivity to vanadate has been reported to be tissue-specific and modulated by various metabolites in other plant systems (Serrano, 1983;Stallaert et al, 1994), an additional study was conducted to compare the efficiency of vanadate inhibition of PM ATPase from different tissues of potato plants.…”