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Globular structures in roots accumulate phosphorus to extremely high concentrations following phosphorus addition

  • Megan H. Ryan
  • Parwinder Kaur
  • Nazanin K. Nazeri
  • Peta L. Clode
  • Gabriel Keeble-Gagnère
  • Ashlea L. Doolette
  • Ronald J. Smernik
  • Olivier Van Aken
  • Dion Nicol
  • Hayato Maruyama
  • Tatsuhiro Ezawa
  • Hans Lambers
  • A. Harvey Millar
  • Rudi Appels
Publishing year: 2019
Language: English
Pages: 1987-2002
Publication/Series: Plant Cell and Environment
Volume: 42
Issue: 6
Document type: Journal article
Publisher: Wiley-Blackwell

Abstract english

Crops with improved uptake of fertilizer phosphorus (P) would reduce P losses and confer environmental benefits. We examined how P-sufficient 6-week-old soil-grown Trifolium subterraneum plants, and 2-week-old seedlings in solution culture, accumulated P in roots after inorganic P (Pi) addition. In contrast to our expectation that vacuoles would accumulate excess P, after 7 days, X-ray microanalysis showed that vacuolar [P] remained low (<12 mmol kg
). However, in the plants after P addition, some cortex cells contained globular structures extraordinarily rich in P (often >3,000 mmol kg
), potassium, magnesium, and sodium. Similar structures were evident in seedlings, both before and after P addition, with their [P] increasing threefold after P addition. Nuclear magnetic resonance (NMR) spectroscopy showed seedling roots accumulated Pi following P addition, and transmission electron microscopy (TEM) revealed large plastids. For seedlings, we demonstrated that roots differentially expressed genes after P addition using RNAseq mapped to the T. subterraneum reference genome assembly and transcriptome profiles. Among the most up-regulated genes after 4 hr was TSub_g9430.t1, which is similar to plastid envelope Pi transporters (PHT4;1, PHT4;4): expression of vacuolar Pi-transporter homologs did not change. We suggest that subcellular P accumulation in globular structures, which may include plastids, aids cytosolic Pi homeostasis under high-P availability.


  • Plant Biotechnology
  • Botany
  • nuclear magnetic resonance spectroscopy
  • phosphorous efficient crops
  • plastids
  • roots
  • vacuoles
  • X-ray microanalysis


  • ISSN: 0140-7791
Olivier van Aken
E-mail: olivier [dot] van_aken [at] biol [dot] lu [dot] se

Senior lecturer

Molecular Cell Biology

+46 46 222 94 13



Research group

Plant Biology



Doctoral students and postdocs

PhD students, main supervisor

Cuong Tran