Dataset Information

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

ABSTRACT: Phosphorus is essential for plant viability. Phosphate-starved plants trigger membrane lipid remodeling to replace membrane phospholipids by non-phosphorus galactolipids presumably to acquire scarce phosphate source. Phosphoethanolamine/phosphocholine phosphatase 1 (PECP1) and phosphate starvation-induced gene 2 (PS2) belong to an emerging class of phosphatase induced by phosphate starvation and dephosphorylates phosphocholine and phosphoethanolamine (PEtn) in vivo. However, detailed spatiotemporal expression pattern as well as subcellular localization has not been investigated yet. Here, by constructing transgenic plants harboring functional translational promoter-reporter fusion system, we showed the expression pattern of PECP1 and PS2 in different tissues and in response to phosphate starvation. Besides, the Venus fluorescent reporter revealed that both are localized at the ER. Characterization of transgenic plants that overexpress PECP1 or PS2 showed that their activity toward PEtn may be different in vivo. We suggest that PECP1 and PS2 are ER-localized phosphatases that show similar expression pattern yet have a distinct substrate specificity in vivo.

SUBMITTER: Angkawijaya AE

PROVIDER: S-EPMC6549246 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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

Angkawijaya Artik Elisa AE Ngo Anh H AH Nguyen Van C VC Gunawan Farrel F Nakamura Yuki Y

Frontiers in plant science 20190529

Phosphorus is essential for plant viability. Phosphate-starved plants trigger membrane lipid remodeling to replace membrane phospholipids by non-phosphorus galactolipids presumably to acquire scarce phosphate source. Phosphoethanolamine/phosphocholine phosphatase 1 (PECP1) and phosphate starvation-induced gene 2 (PS2) belong to an emerging class of phosphatase induced by phosphate starvation and dephosphorylates phosphocholine and phosphoethanolamine (PEtn) <i>in vivo</i>. However, detailed spat ...[more]

PMID: 31191578

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Project description:BackgroundMagnetic resonance spectroscopy (MRS) studies have identified elevated levels of the phospholipid precursor phosphocholine (PC) and phosphoethanolamine (PE) as metabolic hallmarks of cancer. Unusually, however, PC and PE levels are reduced in mutant isocitrate dehydrogenase 1 (IDHmut) gliomas that produce the oncometabolite 2-hydroxyglutarate (2-HG) relative to wild-type IDH1 (IDHwt) gliomas. The goal of this study was to determine the molecular mechanism underlying this unusual metabolic reprogramming in IDHmut gliomas.MethodsSteady-state PC and PE were quantified using 31P-MRS. To quantify de novo PC and PE synthesis, we used 13C-MRS and measured flux to 13C-PC and 13C-PE in cells incubated with [1,2-13C]-choline and [1,2-13C]-ethanolamine. The activities of choline kinase (CK) and ethanolamine kinase (EK), the enzymes responsible for PC and PE synthesis, were quantified using 31P-MR-based assays. To interrogate the role of 2-HG, we examined IDHwt cells incubated with 2-HG and, conversely, IDHmut cells treated with the IDHmut inhibitor AGI-5198. To examine the role of hypoxia-inducible factor 1-α (HIF-1α), we silenced HIF-1α using RNA interference. To confirm our findings in vivo and in the clinic, we studied IDHwt and IDHmut orthotopic tumor xenografts and glioma patient biopsies.ResultsDe novo synthesis of PC and PE was reduced in IDHmut cells relative to IDHwt. Concomitantly, CK activity and EK activity were reduced in IDHmut cells. Pharmacological manipulation of 2-HG levels established that 2-HG was responsible for reduced CK activity, EK activity, PC and PE. 2-HG has previously been reported to stabilize levels of HIF-1α, a known regulator of CK activity. Silencing HIF-1α in IDHmut cells restored CK activity, EK activity, PC and PE to IDHwt levels. Our findings were recapitulated in IDHmut orthotopic tumor xenografts and, most importantly, in IDHmut patient biopsies, validating our findings in vivo and in the clinic.ConclusionsThis study identifies, to our knowledge for the first time, a direct role for 2-HG in the downregulation of CK and EK activity, and thereby, PC and PE synthesis in IDHmut gliomas. These results highlight the unusual reprogramming of phospholipid metabolism in IDHmut gliomas and have implications for the identification of MRS-detectable metabolic biomarkers associated with 2-HG status.

Project description:The fine-tuning of inorganic phosphate (Pi) for enhanced use efficiency has long been a challenging subject in agriculture, particularly in regard to rice as a major crop plant. Among ribonucleases (RNases), the RNase T2 family is broadly distributed across kingdoms, but little has been known on its substrate specificity compared to RNase A and RNase T1 families. Class I and class II of the RNase T2 family are defined as the S-like RNase (RNS) family and have showed the connection to Pi recycling in Arabidopsis. In this study, we first carried out a phylogenetic analysis of eight rice and five Arabidopsis RNS genes and identified mono-specific class I and dicot-specific class I RNS genes, suggesting the possibility of functional diversity between class I RNS family members in monocot and dicot species through evolution. We then compared the in silico expression patterns of all RNS genes in rice and Arabidopsis under normal and Pi-deficient conditions and further confirmed the expression patterns of rice RNS genes via qRT-PCR analysis. Subsequently, we found that most of the OsRNS genes were differentially regulated under Pi-deficient treatment. Association of Pi recycling by RNase activity in rice was confirmed by measuring total RNA concentration and ribonuclease activity of shoot and root samples under Pi-sufficient or Pi-deficient treatment during 21 days. The total RNA concentrations were decreased by < 60% in shoots and < 80% in roots under Pi starvation, respectively, while ribonuclease activity increased correspondingly. We further elucidate the signaling pathway of Pi starvation through upregulation of the OsRNS genes. The 2-kb promoter region of all OsRNS genes with inducible expression patterns under Pi deficiency contains a high frequency of P1BS cis-acting regulatory element (CRE) known as the OsPHR2 binding site, suggesting that the OsRNS family is likely to be controlled by OsPHR2. Finally, the dynamic transcriptional regulation of OsRNS genes by overexpression of OsPHR2, ospho2 mutant, and overexpression of OsPT1 lines involved in Pi signaling pathway suggests the molecular basis of OsRNS family in Pi recycling via RNA decay under Pi starvation.

Dataset Information

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

Publications

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

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