Membrane Particles, Proteins and ATPase Activity of Tonoplast Vesicles of Mesembryanthemum crystallinum in the C‐3 and CAM State*

Abstract

Dimensions and area densities of membrane particles were studied by electron microscopy of replicas of freeze‐fractured suspensions of tonoplast vesicles of Mesembryanthemum crystallinum L. in the C‐3 state and after induction of crassulacean acid metabolism (CAM) by salinity. The results are compared with the relative contribution of tonoplast‐ATPase protein to total membrane protein obtained from integration of elution profiles in size‐exclusion chromatography. Coverage of tonoplast area by globular membrane particles was 20% and 36 % and ATPase in relation to total membrane protein was 33 % and 35 % in C‐3 and CAM M. crystallinum, respectively. Thus, by order of magnitude, it is most likely that the particles represent the ATPase. In Kalanchoë daigremontiana Hamet et Perrier de la Bâthie the ATPase also constituted 36% of total tonoplast protein. Induction of CAM in M. crystallinum was associated with an increase in specific ATPase activity of the tonoplast and an increase of the size and area coverage of tonoplast particles, whereas the relative contribution of ATPase protein to total tonoplast protein and the molecular mass of the ATPase holoenzyme, as seen in size‐exclusion chromatography, remained almost unchanged.

Dynamics of tonoplast proton pumps and other tonoplast proteins of Mesembryanthemum crystallinum L. during the induction of Crassulacean acid metabolism

“…The fact that these kinetic differences are influenced by the presence of detergent indicates that the two ATPase subunits induced during the transition to CAM are probably involved in the interactions between the enzyme and the membrane and in the regulation of ATPase activity. This also relates to the observations of Klink et al (1989)who found that the area covered by the tonoplast ATPase in freeze-fractures suspensions of tonoptast vesicles from leaves of M. crystallinum was higher in the CAM state than in the C3 state. If the subunits induced are indeed involved in the interactions of the enzyme with the membrane and in the regulation of the ATPase, the different subunit of the ATPase in the two metabolic states-like the different subunit composition reported for the vacuolar ATPase from other sources -probably reflects the changed acidification requirement in the vacuole.…”

“…Tonoplast vesicles were prepared after homogenization of the protoplasts by density-gradient centrifugation on a 24% sucrose cushion according to Klink et al (1989). These methods were modified by adjusting the osmotic pressure of all solutions for the treatment of intact protoplasts with mannitol to the osmotic pressure in the cell sap of the corresponding samples.…”

ATPase Activities and Membrane Fine Structure of Rhizodermal Cells from Sorghum and Spartina Roots Grown Under Mild Salt Stress

“…with other investigations on root tissues (Robards and Clarkson, 1984;Wolfe, 1979Wolfe, , 1987 and on isolated vacuoles of Mesembryanthemum (Klink et al, 1990). The authors correlate differences of IMP frequencies between EF and PF faces with biochemical and/or physiological differences, especially those of ATPase activities (Branton, 1969;Fineran, 1970;Lauchli, 1980, 1983;Klink et al, 1990). The EF faces are exposed to the apoplast and the vacuole which represent spaces with relatively low metabolic activities.…”

Phenotypic changes in the fluidity of the tonoplast membrane of crassulacean-acid-metabolism plants in response to temperature and salinity stress

“…Conversely, there were considerable changes in the proteins of the tonoplast, both qualitatively in the tonoplastpeptide patterns (Bremberger et al 1988;Bremberger and Liittge 1992) and quantitatively regarding the fine structure of the tonoplast with respect to its proteins (Klink et al 1990). Thus, we favour the view that the observed changes in the thermotropic phase behavior are due to an altered lipid-protein interaction of the tonoplast proteins rather than to changes in the fluidity of the lipid moiety itself.…”