Sorption of Aluminum to Plasma Membrane Vesicles Isolated from Roots of Scout 66 and Atlas 66 Cultivars of Wheat

Abstract

To further elucidate the mechanisms of differential genotypic tolerance to AI, plasma membrane (PM) vesicles were isolated from whole roots, root tips, and tipless roots of AI3+-sensitive and AI3+-tolerant cultivars (cv) of wheat (Triticum aestivum 1. cv Scout 66 and cv Atlas 66, respectively). Vesicles from cv Scout root tips sorbed more AI than vesicles prepared from any other source. The intrinsic surface-charge density of vesicles isolated from cv Scout was 26% more negative than vesicles from cv Atlas (-37.2 versus -29.5 millicoulombs m-'). Crowth experiments indicated that cv Scout is slightly more sensitive to La3+ than is cv Atlas, that the cultivars are equally sensitive to H+, and that cv Atlas is slightly more sensitive to SeO,' -.l h e difference in sensitivity to AI3+ was very large; for a 50% inhibition, a 16-fold greater activity of AI3+ was required for cv Atlas. Using a newly developed Couy-ChapmanStern model for ion sorption to the P M together with growthresponse curves, we estimate that the difference i n surface-charge density can account for the slightly greater sensitivity of cv Scout to cationic toxicants and the slightly greater sensitivity of cv Atlas to anionic toxicants. According to our estimates the differences in PM surface negativity and AI sorptive capacity probably account for some of the difference in sensitivity to AI3+, but the greater part of the difference probably arises from other tolerance mechanisms expressed in cv Atlas root tips that reduce the amount of AI3+ that can reach the PM.

Effect of aluminium on peroxidase activity in roots of Al-sensitive and Al-resistant barley cultivars

“…It has been suggested that Al-membrane interaction causes structural changes of phospholipide bilayer and accelerates their peroxidation, which affects the function of membranes, such as permeability and membrane protein activities (Cakmak and Horst 1991). The relationship between plasma membrane surface negativity and sensitivity to Al also supports the idea about the membranes as a target site of Al toxicity (Yermiyahu et al 1997). Recently, it has been reported that Al facilitates Fe-mediated free radical production and thus lipid peroxidation, which is a direct cause of plasma membrane disruption and cell death (Yamamoto et al 1997).…”

Early events responsible for aluminum toxicity symptoms in suspension‐cultured tobacco cells

“…The differences in the magnitude of negative charges on the surface of the plasma membrane are expected to differentially attract the positively charged Al ions (Yermiyahu et al, 1997;Ahn et al, 2004), which may alter phospholipid profile thereby affecting lipid-mediated signaling (Kochian, 1995;Matsumoto, 2000). Such alterations of electrical properties of the membrane surface may destabilize the PM.…”

“…Changes in the zeta potential are one of the early responses to Al toxicity (Miyasaka et al, 1989;Yermiyahu et al, 1997), possibly owing to Al binding onto the PM. The differences in the magnitude of negative charges on the surface of the plasma membrane are expected to differentially attract the positively charged Al ions (Yermiyahu et al, 1997;Ahn et al, 2004), which may alter phospholipid profile thereby affecting lipid-mediated signaling (Kochian, 1995;Matsumoto, 2000).…”

“…Scout was 26% more negative than that of vesicles from cv. Atlas, allowing more Al to bind to the Scout vesicles (Yermiyahu et al ., 1997), and causing greater Al toxicity. In line with these observations, greater depolarization of zeta potential was observed recently in vesicles isolated from Al-sensitive ES8 near-isogenic wheat line compared with the Al-tolerant ET8 (Ahn et al ., 2004).…”

Plasma Membrane Lipids Are the Powerful Components for Early Stage Aluminum Tolerance in Triticale

“…We established a short-term A1 tolerance screening technique that is useful for the real time identification of the induction of differential A1 tolerance among plant species. Although several reports have focused on the significance of PM lipid in A1 tolerance (Deleers et al 1985;Zhang et al 1996;Yermiyahu et al 1997;Ishikawa and Wagatsuma 1998;Ishikawa et al 2001), there has not yet been any direct demonstration. Liposomes and synthetic lipid bilayer vesicles frequently utilized for permeability experiments have several disadvantages, such as a very small inner aqueous phase, size distribution and fragility (Okahata and Seki 1984).…”