Lack of the Golgi phosphate transporter PHT4;6 causes strong developmental defects, constitutively activated disease resistance mechanisms and altered intracellular phosphate compartmentation in Arabidopsis

Plant J. 2012 Dec;72(5):732-44. doi: 10.1111/j.1365-313X.2012.05106.x. Epub 2012 Oct 12.


The Golgi-located phosphate exporter PHT4;6 has been described as involved in salt tolerance but further analysis on the physiological impact of PHT4;6 remained elusive. Here we show that PHT4;6-GFP is targeted to the trans-Golgi compartment and that loss of function of this carrier protein has a dramatic impact on plant growth and development. Knockout mutants of pht4;6 exhibit a dwarf phenotype that is complemented by the homologous gene from rice (Oryza sativa). Interestingly, pht4;6 mutants show altered characteristics of several Golgi-related functions, such as an altered abundance of certain N-glycosylated proteins, altered composition of cell-wall hemicelluose, and higher sensitivity to the Golgi α-mannosidase and the retrograde transport inhibitors kifunensine and brefeldin A, respectively. Moreover, pht4;6 mutants exhibit a 'mimic disease' phenotype accompanied by constitutively activated pathogen defense mechanisms and increased resistance against the virulent Pseudomonas syringae strain DC3000. Surprisingly, pht4;6 mutants also exhibit phosphate starvation symptoms, as revealed at the morphological and molecular level, although total Pi levels in wild-type and pht4;6 plants are similar. This suggested that subcellular Pi compartmentation was impaired. By use of nuclear magnetic resonance (NMR), increased Pi concentration was detected in acidic compartments of pht4;6 mutants. We propose that impaired Pi efflux from the trans-Golgi lumen results in accumulation of inorganic phosphate in other internal compartments, leading to low cytoplasmic phosphate levels with detrimental effects on plant performance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkaloids / pharmacology
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / growth & development
  • Arabidopsis / metabolism*
  • Arabidopsis / microbiology
  • Arabidopsis Proteins / genetics*
  • Arabidopsis Proteins / metabolism
  • Brefeldin A / pharmacology
  • Cell Wall / chemistry
  • Disease Resistance
  • Gene Knockdown Techniques
  • Genetic Complementation Test
  • Golgi Apparatus / genetics
  • Golgi Apparatus / metabolism*
  • Mutation
  • Oryza / genetics
  • Phosphate Transport Proteins / genetics*
  • Phosphate Transport Proteins / metabolism
  • Plant Diseases / microbiology
  • Plants, Genetically Modified
  • Polysaccharides / metabolism
  • Pseudomonas syringae / pathogenicity
  • alpha-Mannosidase / metabolism


  • Alkaloids
  • Arabidopsis Proteins
  • PHT4;6 protein, Arabidopsis
  • Phosphate Transport Proteins
  • Polysaccharides
  • kifunensine
  • Brefeldin A
  • hemicellulose
  • alpha-Mannosidase