Arabidopsis PFA-DSP-type phosphohydrolases target specific inositol pyrophosphate messengers

Abstract

Inositol pyrophosphates are signaling molecules containing at least one phosphoanhydride bond that regulate a wide range of cellular processes in eukaryotes. With a cyclic array of phosphate esters and diphosphate groups around myo-inositol, these molecular messengers possess the highest charge density found in nature. Recent work deciphering inositol pyrophosphate biosynthesis in Arabidopsis revealed important functions of these messengers in nutrient sensing, hormone signalling and plant immunity. However, despite the rapid hydrolysis of these molecules in plant extracts, very little is known about the molecular identity of the phosphohydrolases that convert these messengers back to their inositol polyphosphate precursors. Here, we investigate whether Arabidopsis Plant and Fungi Atypical Dual Specificity Phosphatases (PFA-DSP1-5) catalyze inositol pyrophosphate phosphohydrolase activity. We find that recombinant proteins of all five Arabidopsis PFA-DSP homologs display phosphohydrolase activity with a high specificity for the 5-β-phosphate of inositol pyrophosphates. We further show that heterologous expression of Arabidopsis PFA-DSP1-5 rescues wortmannin-sensitivity and deranged inositol pyrophosphate homeostasis caused by the deficiency of the PFA-DSP-type inositol pyrophosphate phosphohydrolase Siw14 in yeast. Heterologous expression in Nicotiana benthamiana leaves provided evidence that Arabidopsis PFA-DSP1 also displays 5-β-phosphate specific inositol pyrophosphate phosphohydrolase activity in planta. Our findings lay the biochemical basis and provide the genetic tools to uncover the roles of inositol pyrophosphates in plant physiology and plant development.

Intracellular phosphate recycling systems for survival during phosphate starvation in plants

“…Since it is known that Pi starvation enhances accumulation of reactive oxygen species (ROS), which leads to programmed cell death (Van Camp et al, 1998;Overmyer et al, 2000;Tyburski et al, 2009;Yoshitake et al, 2022), that proteins may contribute to plant growth not only through the resupply of Pi from intracellular components but also because increase ROS degradation under Pi starvation. It is known that a phosphohydrolase for inositol pyrophosphates (PP-InsPs), one of the phosphoesters, has a role in Pi starvation response, but it is unclear whether this enzyme is involved in Pi recycling (Gaugler et al, 2022).…”

Protein pyrophosphorylation by inositol phosphates: a novel post-translational modification in plants?

“…Also Siw14, a member of the plant and fungi atypical dual-specificity phosphatases (PFA-DSPs) (Roma-Mateo et al, 2007), is a PP-InsP phosphatase in budding yeast, specifically cleaving 5-InsP 7 at the 5-position (Steidle et al, 2016;Wang et al, 2018). All of the five Arabidopsis PFA-DSPs (AtPFA-DSP1-5) were shown to harbor in vitro PP-InsP phosphohydrolase activity that was highly specific towards the 5b-phosphate (Gaugler et al, 2022;Wang et al, 2022b). Increased AtPFA-DSP1 expression in an Arabidopsis T-DNA activator line and heterologous expression of AtPFA-DSP1 in Nicotiana benthamiana both led to a decrease in 5-InsP 7 and 1,5-InsP 8 levels, suggesting a DSP-dependent degradation of these PP-InsP species in planta as well (Gaugler et al, 2022).…”

“…All of the five Arabidopsis PFA-DSPs (AtPFA-DSP1-5) were shown to harbor in vitro PP-InsP phosphohydrolase activity that was highly specific towards the 5b-phosphate (Gaugler et al, 2022;Wang et al, 2022b). Increased AtPFA-DSP1 expression in an Arabidopsis T-DNA activator line and heterologous expression of AtPFA-DSP1 in Nicotiana benthamiana both led to a decrease in 5-InsP 7 and 1,5-InsP 8 levels, suggesting a DSP-dependent degradation of these PP-InsP species in planta as well (Gaugler et al, 2022).…”