Superior aluminium (Al) tolerance of Stylosanthes is achieved mainly by malate synthesis through an Al-enhanced malic enzyme, SgME1

New Phytol. 2014 Apr;202(1):209-219. doi: 10.1111/nph.12629. Epub 2013 Dec 11.


Stylosanthes (stylo) is a dominant leguminous forage in the tropics. Previous studies suggest that stylo has great potential for aluminium (Al) tolerance, but little is known about the underlying mechanism. A novel malic enzyme, SgME1, was identified from the Al-tolerant genotype TPRC2001-1 after 72 h Al exposure by two-dimensional electrophoresis, and the encoding gene was cloned and characterized via heterologous expression in yeast, Arabidopsis thaliana and bean (Phaseolus vulgaris) hairy roots. Internal Al detoxification might be mainly responsible for the 72 h Al tolerance of TPRC2001-1, as indicated by 5.8-fold higher root malate concentrations and approximately two-fold higher Al concentrations in roots and root symplasts of TPRC2001-1 than those of the Al-sensitive genotype Fine-stem. An accompanying increase in malate secretion might also reduce a fraction of Al uptake in TPRC2001-1. Gene and protein expression of SgME1 was only enhanced in TPRC2001-1 after 72 h Al exposure. Overexpressing SgME1 enhanced malate synthesis and rescued yeast, A. thaliana and bean hairy roots from Al toxicity via increasing intracellular malate concentrations and/or accompanied malate exudation. These results provide strong evidence that superior Al tolerance of stylo is mainly conferred by Al-enhanced malate synthesis, functionally controlled by SgME1.

Keywords: Stylosanthes; aluminium (Al) tolerance; malate exudation; malate synthesis; malic enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Physiological / drug effects*
  • Aluminum / toxicity*
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / physiology
  • Electrophoresis, Gel, Two-Dimensional
  • Fabaceae / drug effects
  • Fabaceae / enzymology*
  • Fabaceae / genetics
  • Fabaceae / physiology*
  • Genotype
  • Malate Dehydrogenase / isolation & purification
  • Malate Dehydrogenase / metabolism*
  • Malates / metabolism*
  • Oryza / drug effects
  • Oryza / physiology
  • Phenotype
  • Plant Exudates / metabolism
  • Plant Roots / drug effects
  • Plant Roots / growth & development
  • Plants, Genetically Modified
  • Saccharomyces cerevisiae / drug effects
  • Saccharomyces cerevisiae / physiology


  • Malates
  • Plant Exudates
  • malic acid
  • Aluminum
  • Malate Dehydrogenase
  • malate dehydrogenase (decarboxylating)