Significant Role of the Plasma Membrane Lipid Bilayers in Aluminum Tolerance of Plants

Abstract

AbstractWe propose a new aluminum (Al) tolerance mechanism which should be discriminated from the exclusion mechanism: plasma membrane (PM) lipid bilayers barrier mechanism (Abbreviation: Plasma membrane lipid mechanism). It is defined as the retardation of Al permeation through the PM lipid bilayers ascribed to the specific composition of lipid molecules in the PM. The lipid phase separation response of the PM in the root tip portion of plants caused by the binding of phospholipids with Al3+ is an important first step in Al toxicity. This response develops most strongly in the elongation zone of the root tip by increasing the distances between solid state lipid aggregates. Sterols are independent of the action of Al3+ because of their electrical neutrality. Purified PMs from Al-tolerant cultivars showed less permeability than PMs from Al-sensitive cultivars without the participation of organic acid anion exudation. Lowering the phospholipid content and the increasing the sterol content of PMs from root tips produce PMs with less surface negativity and is a common strategy for Al tolerance in several plant species. PAH encoding phosphatidate phosphohydrolase and HMG encoding 3-hydroxy-3-methylglutaryl CoA reductase are speculated to be promising candidate genes for lowering the phospholipid content and for increasing the sterol content, respectively, to generate new Al-tolerant plants. Phenolics are present in high concentrations in plants, especially in hyper Al-tolerant plants; however, their existence within the lipid bilayers of root PMs needs to be clarified to understand their potential to reduce PM permeability. Combined studies on the ionome and lipidome of plant PMs may provide insights useful for breeding plants with multiple tolerances to complex ionic environments.KeywordsMethylene BlueLipid BilayerFree SterolOrganic Acid AnionLipid Phase SeparationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.