The Phosphate Fast-Responsive Genes PECP1 and PPsPase1 Affect Phosphocholine and Phosphoethanolamine Content

Abstract

Phosphate starvation-mediated induction of the HAD-type phosphatases PPsPase1 (AT1G73010) and PECP1 (AT1G17710) has been reported in Arabidopsis (Arabidopsis thaliana). However, little is known about their in vivo function or impact on plant responses to nutrient deficiency. The preferences of PPsPase1 and PECP1 for different substrates have been studied in vitro but require confirmation in planta. Here, we examined the in vivo function of both enzymes using a reverse genetics approach. We demonstrated that PPsPase1 and PECP1 affect plant phosphocholine and phosphoethanolamine content, but not the pyrophosphate-related phenotypes. These observations suggest that the enzymes play a similar role in planta related to the recycling of polar heads from membrane lipids that is triggered during phosphate starvation. Altering the expression of the genes encoding these enzymes had no effect on lipid composition, possibly due to compensation by other lipid recycling pathways triggered during phosphate starvation. Furthermore, our results indicated that PPsPase1 and PECP1 do not influence phosphate homeostasis, since the inactivation of these genes had no effect on phosphate content or on the induction of molecular markers related to phosphate starvation. A combination of transcriptomics and imaging analyses revealed that PPsPase1 and PECP1 display a highly dynamic expression pattern that closely mirrors the phosphate status. This temporal dynamism, combined with the wide range of induction levels, broad expression, and lack of a direct effect on Pi content and regulation, makes PPsPase1 and PECP1 useful molecular markers of the phosphate starvation response.Plant growth is highly sensitive to a lack of phosphate (Pi); hence, the application of Pi fertilizers has become standard practice for high-throughput crop production (Cordell et al., 2009). Most phosphorus in the soil is not available to plants, as it is combined with other minerals or parts of organic compounds (Bieleski, 1973;Raghothama and Karthikeyan, 2005). Only a small fraction of soluble Pi (usually present at a concentration of ,10 mM in the soil) can be taken up by plants.Although growth is not optimal under limiting conditions, plants can withstand changing Pi concentrations within heterogeneous soils or in the external nutrient supply that can lead to reprogramming of their metabolism and architecture (Hammond et al., 2003;Péret et al., 2011;Plaxton and Tran, 2011). Root architecture can be modified to facilitate Pi uptake by favoring the development of lateral roots (at the expense of primary root elongation in many plants including Arabidopsis), increasing the density and length of root hairs, and limiting the development of aerial parts (López-Bucio et al., 2002;Svistoonoff et al., 2007;Gruber et al., 2013). Pi uptake mechanisms are enhanced at the root/soil interface, particularly through the stimulation of Pi transport activity (Mudge et al., 2002;Shin et al., 2004;Nussaume et al., 2011; Ayadi et al., 2015). In parallel, mobilization of Pi sources fr...

Under phosphate starvation conditions, Fe and Al trigger accumulation of the transcription factor STOP1 in the nucleus of Arabidopsis root cells

“…By contrast, the expression of SPX1 is induced only in –Pi conditions, whatever the pH or the gelling agent used to prepare the growth medium (Figure a). All these observations were confirmed by quantitative reverse transcriptase‐polymerase chain reaction (qRT‐PCR) (Figures b and S2), and with the pyrophosphatase [PPi]‐specific phosphatase1 ( PPsPase1 ) gene as an additional marker whose expression is highly stimulated by Pi deficiency (Hanchi et al ., ) (Figure b).…”

A Methyltransferase Trio Essential for Phosphatidylcholine Biosynthesis and Growth

“…Indeed, none of the putative Cho kinases (CEK1, 2, and 3) affect PC contents when knocked out (Lin et al, 2015). In addition, double knock out of two PCho phosphatases (PECP1 and PS2) does not affect PC (Hanchi et al, 2018). Gene knockout studies have shown that SDC1, CEK4, and PECT1 are essential in embryogenesis because their null mutants show an embryonic-lethal phenotype (Mizoi et al, 2006;Lin et al, 2015;Yunus et al, 2016).…”

Expression Profiles of 2 Phosphate Starvation-Inducible Phosphocholine/Phosphoethanolamine Phosphatases, PECP1 and PS2, in Arabidopsis

“…Indeed, the double mutant pecp1-1 ps2-3 showed reduced Cho content under phosphate starvation (Angkawijaya and Nakamura, 2017). Moreover, overexpression of PECP1 (Hanchi et al, 2018; Tannert et al, 2018) or PS2 (Hanchi et al, 2018) decreased PCho content in planta . However, phosphatidylethanolamine (PE) content also decreases in response to phosphate starvation (Essigmann et al, 1998) and NPC4 and 5 can hydrolyze PE in vitro (Nakamura et al, 2005; Gaude et al, 2008).…”

“…According to in vitro study, PECP1 dephosphorylates PEtn (May et al, 2012). In vivo , overexpression of PECP1 or PS2 decreases PEtn content (Hanchi et al, 2018). However, it is unknown whether changes in PEtn contents are due to dephosphorylation activity because Etn content was not analyzed.…”

“…Later, a close homolog of PS2/PPsPase1, named PECP1, was found to be a phosphatase that dephosphorylates major polar head group of phospholipids such as phosphoethanolamine (PEtn) and phosphocholine (PCho) in vitro (May et al, 2012). Although PECP1 but not PS2/PPsPase1 hydrolyzes the phospholipid polar head group in vitro , gene knockout study of the pecp1-1 ps2-3 double mutant (Angkawijaya and Nakamura, 2017) as well as in planta overexpression study (Hanchi et al, 2018) suggest that both are redundant in dephosphorylating the polar head group in vivo . Despite a possible overlapping function of two closely related phosphatases, comparative study on their tissue expression profiles and subcellular localization has not been reported.…”