Apr 25, 2020

ITPK1-Dependent Inositol Polyphosphates Regulate Auxin Responses in Arabidopsis thaliana

BioRxiv : the Preprint Server for Biology
N. P. LahaGabriel Schaaf

Abstract

The combinatorial phosphorylation of myo-inositol results in the generation of different inositol phosphates (InsP), of which phytic acid (InsP6) is the most abundant species in eukaryotes. InsP6 is also the precursor of higher phosphorylated forms called inositol pyrophosphates (PP-InsPs), such as InsP7 and InsP8, which are characterized by a diphosphate moiety and are also ubiquitously found in eukaryotic cells. While PP-InsPs regulate various cellular processes in animals and yeast, their biosynthesis and functions in plants has remained largely elusive because plant genomes do not encode canonical InsP6 kinases. Recently, it was shown that Arabidopsis ITPK1 catalyzes the phosphorylation of InsP6 to the natural 5-InsP7 isomer in vitro. Here, we demonstrate that Arabidopsis ITPK1 contributes to the synthesis of InsP7 in planta. We further find a critical role of ITPK1 in auxin-related processes including primary root elongation, leaf venation, thermomorphogenic and gravitropic responses, and sensitivity towards exogenously applied auxin. Notably, 5-InsP7 binds to recombinant auxin receptor complex, consisting of the F-Box protein TIR1, ASK1 and the transcriptional repressor IAA7, with high affinity. Furthermore, a specific in...Continue Reading

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Mentioned in this Paper

Genome
Proteins, Recombinant DNA
Host (Organism)
Genomics
Chromosomes
Molecular Biology
Laboratory Culture
Open Reading Frames
Biomedicine
Escherichia coli

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