Get started
Work

Functional characterization of inositol pyrophosphate pyrophosphatases in plants

Year: 2025
Type: dissertation
Abstract: The consequences of the climate and biodiversity crisis present an increasingly challenge for the agricultural sector to ensure food security for a growing world population. The optimal nutrient supply of plants is a critical factor in maintaining or increasing yields, especially of essential macronutrients such as phosphorus (P). It is therefore important to gain a deeper understanding of the processes involved in P uptake, in form of inorganic phosphate (Pi), and the mechanisms regulating Pi homeostasis in plants. Recent research has identified the involvement of the signaling molecules inositol pyrophosphates (PP-InsPs) in the process of Pi signaling and homeostasis in plants. The biosynthesis of PP-InsPs relies on balanced phosphorylation and dephosphorylation of inositol phosphates (InsPs) and PP-InsPs. However, the current state of knowledge regarding PP-InsP dephosphorylation is notably limited in comparison to InsP/PP-InsP phosphorylation. Therefore, the objective of this thesis was to identify and characterize putative PP-InsP pyrophosphatases in plants. We found that recombinant proteins of all five Arabidopsis Plant and Fungi Atypical Dual Specificity Phosphatases (PFA-DSP1-5) display pyrophosphatase activity with a high specificity for the 5 β-phosphate of PP-InsPs. Heterologous expression in Nicotiana benthamiana leaves provided evidence that Arabidopsis PFA-DSP1 also displays a 5-β-phosphate-specific PP-InsP pyrophosphatase activity in planta. Moreover, we identified a family of Arabidopsis NUDIX hydrolases (NUDTs) that group into two closely related subclades. Through in vitro assays, heterologous expression systems, and higher-order gene-edited mutants, we found that subclade I NUDTs preferentially hydrolyze 4-InsP7, while subclade II NUDTs target 3-InsP7. In higher-order mutants of subclade II NUDTs, we observed defects in both Pi and iron homeostasis, accompanied by increased levels of 1/3-InsP7 and 5-InsP7. Ectopic expression of NUDTs from both subclades induced local Pi starvation responses (PSRs), while RNA-seq analyses comparing WT and nudt12/13/16 loss-of-function plants indicate additional PSR-independent roles and a potential involvement of 1/3-InsP7 in the regulation of plant defense. Collectively, the results presented in thesis show not only new insights into the roles of PFA DSPs and NUDTs in regulating PP-InsP signaling pathways in plants, but also provide the genetic tools to uncover more general roles of PP-InsPs in plant physiology and plant development.
DOI: 10.48565/bonndoc-543
Institution: University of Bonn
Language: English
Subfield: Plant Science
Open Access status: green
OpenAlex ID: W6929259580
Cites:
Cited by:
Related to: