ITPK1 is an InsP6/ADP phosphotransferase that controls phosphate signaling in Arabidopsis

Riemer, E and Qiu, D and Laha, D and Harmel, RK and Gaugler, P and Gaugler, V and Frei, M and Hajirezaei, M-R and Laha, NP and Krusenbaum, L and Schneider, R and Saiardi, A and Fiedler, D and Jessen, HJ and Schaaf, G and Giehl, RFH (2021) ITPK1 is an InsP6/ADP phosphotransferase that controls phosphate signaling in Arabidopsis. In: Molecular Plant .

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Abstract

In plants, phosphate (Pi) homeostasis is regulated by the interaction of PHR transcription factors with stand-alone SPX proteins, which act as sensors for inositol pyrophosphates. In this study, we combined different methods to obtain a comprehensive picture of how inositol (pyro)phosphate metabolism is regulated by Pi and dependent on the inositol phosphate kinase ITPK1. We found that inositol pyrophosphates are more responsive to Pi than lower inositol phosphates, a response conserved across kingdoms. Using the capillary electrophoresis electrospray ionization mass spectrometry (CE-ESI-MS) we could separate different InsP7 isomers in Arabidopsis and rice, and identify 4/6-InsP7 and a PP-InsP4 isomer hitherto not reported in plants. We found that the inositol pyrophosphates 1/3-InsP7, 5-InsP7, and InsP8 increase several fold in shoots after Pi resupply and that tissue-specific accumulation of inositol pyrophosphates relies on ITPK1 activities and MRP5-dependent InsP6 compartmentalization. Notably, ITPK1 is critical for Pi-dependent 5-InsP7 and InsP8 synthesis in planta and its activity regulates Pi starvation responses in a PHR-dependent manner. Furthermore, we demonstrated that ITPK1-mediated conversion of InsP6 to 5-InsP7 requires high ATP concentrations and that Arabidopsis ITPK1 has an ADP phosphotransferase activity to dephosphorylate specifically 5-InsP7 under low ATP. Collectively, our study provides new insights into Pi-dependent changes in nutritional and energetic states with the synthesis of regulatory inositol pyrophosphates. © 2021 The Authors

Item Type:	Journal Article
Publication:	Molecular Plant
Publisher:	Cell Press
Additional Information:	The copyright for this article belongs to Authors
Department/Centre:	Division of Biological Sciences > Biochemistry
Date Deposited:	03 Dec 2021 08:31
Last Modified:	03 Dec 2021 08:31
URI:	http://eprints.iisc.ac.in/id/eprint/70215

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