A type 5 acid phosphatase gene from Arabidopsis thaliana is induced by phosphate starvation and by some other types of phosphate mobilising/oxidative stress conditions

Abstract

SummaryLow phosphorous availability, a common condition of many soils, is known to stimulate phosphatase activity in plants; however, the molecular details of this response remain mostly unknown. We puri®ed and sequenced the N-terminal region of a phosphate starvation induced acid phosphatase (AtACP5) from Arabidopsis thaliana, and cloned its cDNA and the corresponding genomic DNA. The nucleotide sequence of the cDNA predicted that AtACP5 is synthesised as a 338 amino acid-long precursor with a signal peptide. AtACP5 was found to be related to known purple acid phosphatases, especially to mammal type 5 acid phosphatases. Other similarities with purple acid phosphatases, which contain a dinuclear metal centre, include the conservation of all residues involved in metal ligand binding and resistance to tartrate inhibition. In addition, AtACP5, like other type 5 acid phosphatases, displayed peroxidation activity. Northern hybridisation experiments, as well as in situ glucuronidase (GUS) activity assays on transgenic plants harbouring AtACP5:GUS translational fusions, showed that AtACP5 is not only responsive to phosphate starvation but also to ABA and salt stress. It is also expressed in senescent leaves and during oxidative stress induced by H 2 O 2 , but not by paraquat or salicylic acid. Given its bifunctionality, as it displays both phosphatase and peroxidation activity, we propose that AtACP5 could be involved in phosphate mobilisation and in the metabolism of reactive oxygen species in stressed or senescent parts of the plant.

Structure, function, and regulation of tartrate-resistant acid phosphatase

“…The function of purple plant phosphatases is unknown, the only real clue being the fact that they are inducible in some plants by phosphate deprivation. 25,71 It is possible that elucidation of their function may give insight into the role of TRAP in mammals. Novel structural features of recently discovered plant TRAP enzymes include membrane localization via a GPI anchor in an enzyme purified from duckweed.…”

Attenuation of Phosphate Starvation Responses by Phosphite in Arabidopsis

“…To monitor Piregulated gene expression, we used gene probes coding for an acid phosphatase (AtACP5), a Pi transporter (AtPT2), and a protein of unknown function (At4). These genes are induced by Pi limitation but are repressed in high Pi (Muchhal et al, 1996;del Pozo et al, 1999;Burleigh and Harrison, 1999). Seeds were germinated for 3 d on ϩPi medium and then transferred to ϩPi, ϪPi, and ϪPi/ϩPhi medium.…”

“…These results are in agreement with studies in Brassica sp., which showed that Phi reduced the induction of phosphoenolpyruvate phosphatase, pyrophosphate-dependent phosphofructokinase, and highaffinity Pi uptake in Pi-limiting conditions by 40% to 90% (Carswell et al, 1996(Carswell et al, , 1997. We extended our studies to compare the effect of Pi and Phi on steadystate levels of Pi-responsive mRNAs, which encode a Pi transporter, AtPT2 (Muchhal and Raghothama, 1999), an acid phosphatase, AtACP5 (del Pozo et al, 1999), and an unknown gene product, At4 (Burleigh and Harrison, 1999). Our data clearly indicate that Phi represses Pi starvation-inducible gene expression at the transcript level.…”

“…These include Pi starvation-inducible acid phosphatases with broad substrate specificity (Duff et al, 1994;del Pozo et al, 1999;Baldwin et al, 2001), phosphoenolpyruvate phosphatase and pyrophosphate-dependent phosphofructokinase (Theodorou and Plaxton, 1993), ribonucleases (Green, 1994), phosphodiesterases (Abel et al, 2000), Pi transporters (Raghothama, 2000), and several genes of unknown function (Liu et al, 1997;Burleigh and Harrison, 1999). However, Pi sensory mechanisms and components of the signal transduction pathway(s) that integrate the Pi starvation response of plants have not been identified.…”

Influences of phosphorus starvation on OsACR2.1 expression and arsenic metabolism in rice seedlings

“…In addition to reducing arsenate, OsACR2.1 exhibits phosphatase activity. Phosphatase activities are commonly increased when internal levels of P are depleted (Duff et al 1991;del Pozo et al 1999;Baldwin et al 2001;Vance et al 2003). However, how OsACR2.1 expression is regulated when rice is P limited still needs to be determined.…”