A genetically validated approach for detecting inorganic polyphosphates in plants.

Abstract

Inorganic polyphosphates (polyPs) are linear polymers of orthophosphate units linked by phosphoanhydride bonds. Polyphosphates represent important stores of phosphate and energy, and are abundant in many pro- and eukaryotic organisms. In plants, the existence of polyPs has been established using microscopy and biochemical extraction methods that are now known to produce artifacts. Here we use a polyP-specific dye and a polyP-binding domain to detect polyPs in plant and algal cells. To develop the staining protocol, we induced polyP granules in Nicotiana benthamiana and Arabidopsis cells by heterologous expression of Escherichia coli polyphosphate kinase 1 (PPK1). Over-expression of PPK1 but not of a catalytically impaired version of the enzyme leads to severe growth phenotypes, suggesting that ATP-dependent synthesis and accumulation of polyPs in the plant cytosol is toxic. We next crossed stable PPK1-expressing Arabidopsis lines with plants expressing the polyP-binding domain of E. coli exopolyphosphatase (PPX1c), which co-localized with PPK1-generated polyP granules. These granules were stained by the polyP-specific dye JC-D7 and appeared as electron-dense structures in transmission electron microscopy sections. Using the polyP staining protocol derived from these experiments, we screened for polyP stores in different organs and tissues of both mono- and dicotyledonous plants. While we could not detect polyP granules in higher plants, we could visualize the polyP-rich acidocalcisomes in the green alga Chlamydomonas reinhardtii.

• Authors: Jinsheng Zhu, Sylvain Loubéry, Larissa Broger, Youjun Zhang, Laura Lorenzo-Orts, Anne Utz-Pugin, Alisdair R Fernie, Chang Young-Tae, Michael Hothorn
• Journal: The Plant journal : for cell and molecular biology (Plant J) Vol. 102 Issue 3 Pg. 507-516 (05 2020) ISSN: 1365-313X [Electronic] England
• PMID: 31816134 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: © 2019 The Authors. The Plant Journal © 2019 John Wiley & Sons Ltd.

Chemical References

• Polyphosphates
• Phosphotransferases (Phosphate Group Acceptor)
• polyphosphate kinase

Topics

• Chlamydomonas (metabolism)
• Energy Metabolism (physiology)
• Phosphotransferases (Phosphate Group Acceptor) (metabolism)
• Polyphosphates (metabolism)