Foveoschisis associated with gyrate atrophy in ornithine aminotransferase deficiency: A case report.

Ornithine aminotransferase (OAT) deficiency is an autosomal recessive disease characterized by elevated serum ornithine levels caused by mutations in genes encoding for ornithine aminotransferase, a vitamin B6-dependent mitochondrial matrix enzyme. Gyrate atrophy (GA) is characteristic findings in OAT that characterized by sharply demarcated circular, pigmentary, brain-like areas of chorioretinal atrophy in the peripheral retina. This case report presents rare assosiation between OAT and GA and describes the characteristic imaging findings of this unique, not fully understood clinical entity. The coexistence of GA and foveoschisis is extremely rare in OAT deficiency. We report a case of foveoschisis in a patient with OAT, and we will discuss the possible mechanisms that lead to it. A 24-year-old male patient presented with complaints of decreased vision and nictalopia for 1 year. The patient, who was diagnosed with oat 6 years ago, had typical gyrate atrophy in his Fundus floresein angiography and foveoschisis in his Optical coherence tomography. He was diagnosed with gyrate atrophy and foveoschisis. GA caused by OAT deficiency may present with macular involvement in the form of foveoschisis causing central visual impairment. Ophthalmologists should not ignore detailed fundus examination in children and young patients with visual impairment and should be aware of possible systemic diseases.

Liver-directed gene therapy for ornithine aminotransferase deficiency.

Gyrate atrophy of choroid and retina (GACR) is a chorioretinal degeneration caused by pathogenic variants in the gene encoding ornithine aminotransferase (OAT), an enzyme mainly expressed in liver. Affected patients have increased ornithine concentrations in blood and other body fluids and develop progressive constriction of vision fields leading to blindness. Current therapies are unsatisfactory and better treatments are highly needed. In two mouse models of OAT deficiency that recapitulates biochemical and retinal changes of GACR, we investigated the efficacy of an intravenously injected serotype 8 adeno-associated (AAV8) vector expressing OAT under the control of a hepatocyte-specific promoter. Following injections, OAT-deficient mice showed reductions of ornithine concentrations in blood and eye cups compared with control mice injected with a vector expressing green fluorescent protein. AAV-injected mice showed improved electroretinogram response and partial restoration of retinal structure up to one-year post-injection. In summary, hepatic OAT expression by AAV8 vector was effective at correction of hyperornithinemia and improved function and structure of the retina. In conclusion, this study provides proof-of-concept of efficacy of liver-directed AAV-mediated gene therapy of GACR.

Ornithine aminotransferase and carbamoyl phosphate synthetase 1 involved in ammonia metabolism serve as novel targets for early stages of gastric cancer.

OBJECTIVE: The sensitivity and specificity of current biomarkers for gastric cancer were insufficient. The aim of the present study was to screen novel biomarkers and determine the diagnostic values of ornithine aminotransferase (OAT) and carbamoyl phosphate synthetase 1 (CPS1) for detecting gastric cancer. METHODS: With stable isotope tags, we labelled an initial discovery group of four paired gastric cancer tissue samples and identified with LC-ESI-MS/MS. A validation group of 159 gastric cancer samples and 30 healthy controls were used to validate the candidate targets. GSEA was used to explore the pathways activated in gastric cancer. RESULTS: Four hundred and thirty one proteins were found differentially expressed in gastric cancer tissues. Of these proteins, OAT and CPS1 were found over-expressed in gastric cancer patients, with sensitivity of 70.4% (95% CI: 63.3%-77.6%) and specificity of 80.5% (95% CI: 74.3%-86.7%) for ornithine aminotransferase, and with sensitivity of 68.6% (95% CI: 61.3%-75.8%) and specificity of 73% (95% CI: 66%-79.9%) for carbamoyl phosphate synthetase 1. The co-expression of OAT and CPS1 in gastric cancer tissues has a sensitivity of 81% (95% CI: 73.2%-88.8%) and specificity of 89% (95% CI: 83%-95%). Furthermore, both OAT and CPS1 were overexpressed in patients with local invasion T3 and T4 stages than those in patients with T1 and T2 stages. The co-expression of OAT and CPS1 was strongly correlated with histological grade I 68% (95% CI: 58.7%-77.3%) and TNM stage I/II 52% (95% CI: 42%-62%). The areas under ROC curves were up to 0.758 for the co-expression of OAT and CPS1 in gastric cancer. GSEA results showed that two gene sets and 30 gene sets were activated in OAT high- and CPS1 high-expression patients with gastric cancer, respectively. CONCLUSIONS: The present findings indicated a tight correlation between the co-expression of OAT and CPS1 and the histological grade, local invasion, and TNM stages of gastric cancer. Therefore, OAT and CPS1 might be predictors for gastric cancer invasion and potential targets for anticancer drug design for gastric cancer.

Structural basis of dynamic P5CS filaments.

The bifunctional enzyme Δ1-pyrroline-5-carboxylate synthase (P5CS) is vital to the synthesis of proline and ornithine, playing an essential role in human health and agriculture. Pathogenic mutations in the P5CS gene (ALDH18A1) lead to neurocutaneous syndrome and skin relaxation connective tissue disease in humans, and P5CS deficiency seriously damages the ability to resist adversity in plants. We have recently found that P5CS forms cytoophidia in vivo and filaments in vitro. However, it is difficult to appreciate the function of P5CS filamentation without precise structures. Using cryo-electron microscopy, here we solve the structures of Drosophila full-length P5CS in three states at resolution from 3.1 to 4.3 Å. We observe distinct ligand-binding states and conformational changes for the GK and GPR domains, respectively. Divergent helical filaments are assembled by P5CS tetramers and stabilized by multiple interfaces. Point mutations disturbing those interfaces prevent P5CS filamentation and greatly reduce the enzymatic activity. Our findings reveal that filamentation is crucial for the coordination between the GK and GPR domains, providing a structural basis for the catalytic function of P5CS filaments.

First reported case of pregnancy in a patient with ornithine aminotransferase deficiency.

Ornithine aminotransferase deficiency is a rare autosomalrecessive human inborn error of the metabolism resulting in hyperornithinemia and progressive chorioretinal degeneration (gyrate atrophy) with blindness. There are few reports in the literature and none, to our knowledge, that address this condition during pregnancy. We report on a novel case of ornithine aminotransferase deficiency during pregnancy that was managed actively with arginine and protein restriction with serial amino acid and fetal growth monitoring, resulting in an uncomplicated term live birth.

Heterogeneous phenotypes of Pten-null hepatocellular carcinoma in hepatitis B virus transgenic mice parallels liver lobule zonal gene expression patterns.

Chronic HBV infection is a major cause of hepatocellular carcinoma (HCC) worldwide. The phenotypes of HCC are diverse, in part, due to mutations in distinct oncogenes and/or tumor suppressor genes. These genetic drivers of HCC development have generally been considered as major mediators of tumor heterogeneity. Using the liver-specific Pten-null HBV transgenic mouse model of chronic viral infection, a critical role for liver lobule zone-specific gene expression patterns in determining HCC phenotype and ß-catenin-dependent HBV biosynthesis is demonstrated. These observations suggest that the position of the hepatocyte within the liver lobule, and hence its intrinsic gene expression pattern at the time of cellular transformation, make critical contributions to the properties of the resulting liver tumor. These results may explain why therapies targeting pathways modulated by specific identified tumor driver genes display variable treatment efficacy.

Gyrate Atrophy of the Choroid and Retina: A Review.

Gyrate atrophy (GA) of the choroid and retina is a rare autosomal recessive genetic condition characterized by elevation of the plasma level of the amino acid ornithine due to deficiency of the enzyme ornithine ketoacid aminotransferase. Accumulation of ornithine occurs in various body tissues but leads primarily to characteristic ophthalmic manifestations including myopia, cataract, progressive chorioretinal atrophy, and macular changes. Patients usually present with night blindness that starts in the first decade of life followed by visual field constriction and eventually diminution of the central visual acuity and blindness. The condition has been reported worldwide and its differential diagnosis is broad and includes choroideremia and retinitis pigmentosa. Treatment currently depends on life-long dietary modifications including restriction of the amino acid arginine in diet. This article describes in detail the pathogenesis, clinical features, multimodal imaging findings, and treatment options for GA of the choroid and retina and its complications.

Indoxyl Sulfate Contributes to mTORC1-Induced Renal Fibrosis via The OAT/NADPH Oxidase/ROS Pathway.

Activation of mTORC1 (mechanistic target of rapamycin complex 1) in renal tissue has been reported in chronic kidney disease (CKD)-induced renal fibrosis. However, the molecular mechanisms responsible for activating mTORC1 in CKD pathology are not well understood. The purpose of this study was to identify the uremic toxin involved in mTORC1-induced renal fibrosis. Among the seven protein-bound uremic toxins, only indoxyl sulfate (IS) caused significant activation of mTORC1 in human kidney 2 cells (HK-2 cells). This IS-induced mTORC1 activation was inhibited in the presence of an organic anion transporter inhibitor, a NADPH oxidase inhibitor, and an antioxidant. IS also induced epithelial-mesenchymal transition of tubular epithelial cells (HK-2 cells), differentiation of fibroblasts into myofibroblasts (NRK-49F cells), and inflammatory response of macrophages (THP-1 cells), which are associated with renal fibrosis, and these effects were inhibited in the presence of rapamycin (mTORC1 inhibitor). In in vivo experiments, IS overload was found to activate mTORC1 in the mouse kidney. The administration of AST-120 or rapamycin targeted to IS or mTORC1 ameliorated renal fibrosis in Adenine-induced CKD mice. The findings reported herein indicate that IS activates mTORC1, which then contributes to renal fibrosis. Therapeutic interventions targeting IS and mTORC1 could be effective against renal fibrosis in CKD.

A Case of Foveoschisis Associated with Ornithine Aminotransferase Deficiency and Gyrate Atrophy.

Gyrate atrophy is a metabolic disorder characterised by typical progressive circular chorioretinal atrophy, myopia and early developmental cataract. The disease is caused by deficiency of ornithine aminotransferase (OAT) enzyme. Although OAT is expressed in most tissues of the body, but the main target of the disease appears to be the retina. A case is presented here of a 21-year woman, who came to our clinic with the complaint of decline in central vision for eight months. She had progressive poor night vision and was diagnosed with OAT deficiency five years ago. Her systemic history was unremarkable, except for femoral deep vein thrombosis (DVT) which occurred two years ago. Laboratory tests performed at that time had revealed elevated serum ornithine and low serum lysin levels. Optic coherence tomography (OCT) scans showed foveoschisis bilaterally. In summary, gyrate atrophy may present as macular involvement in the form of foveoschisis and may lead to impaired central vision. Key Words: Foveoschisis, Gyrate atrophy, Ornithine aminotransferase.

Functional Characterization of the Stipa purpurea P5CS Gene under Drought Stress Conditions.

Free proline has multiple functions in plant cells, such as regulating osmotic potential and protecting both proteins and cell membranes. The expression of Δ1-Pyrroline-5-carboxylate synthase (P5CS), a key enzyme in the proline biosynthetic pathway, increases under drought, salt and cold stress conditions, causing plant cells to accumulate large amounts of proline. In this study, we cloned and identified the P5CS gene from Stipa purpurea, which has a full-length of 2196 bp and encodes 731 amino acids. A subcellular localization analysis indicated that SpP5CS localized to the cytoplasm. The ectopic overexpression of SpP5CS in Arabidopsis thaliana resulted in higher proline contents, longer roots, higher survival rates and less membrane damage under drought stress conditions compared with wild-type controls. SpP5CS-overexpressing A. thaliana was more resistant to drought stress than the wild type, whereas the deletion mutant sp5cs was less resistant to drought stress. Thus, SpP5CS may be a potential candidate target gene for increasing plant resistance to drought stress.

Expression of Arabidopsis Ornithine Aminotransferase (AtOAT) encoded gene enhances multiple abiotic stress tolerances in wheat.

KEY MESSAGE: The drought and salt tolerances of wheat were enhanced by ectopic expression of the Arabidopsis ornithine aminotransferase (AtOAT) encoded gene. The OAT was confirmed to play a role in proline biosynthesis in wheat. Proline (Pro) accumulation is a common response to both abiotic and biotic stresses in plants. Ornithine aminotransferase (OAT) is pyridoxal-5-phosphate dependent enzyme involved in plant proline biosynthesis. During stress condition, proline is synthesized via glutamate and ornithine pathways. The OAT is the key enzyme in ornithine pathway. In this study, an OAT gene AtOAT from Arabidopsis was expressed in wheat for its functional characterization under drought, salinity, and heat stress conditions. We found that the expression of AtOAT enhanced the drought and salt stress tolerances of wheat by increasing the proline content and peroxidase activity. In addition, it was confirmed that the expression of AtOAT also played a partial tolerance to heat stress in the transgenic wheat plants. Moreover, quantitative real-time PCR (qRT-PCR) analysis showed that the transformation of AtOAT up-regulated the expression of the proline biosynthesis associated genes TaOAT, TaP5CS, and TaP5CR, and down-regulated that of the proline catabolism related gene TaP5CDH in the transgenic plants under stress conditions. Moreover, the genes involved in ornithine pathway (Orn-OAT-P5C/GSA-P5CR-Pro) were up-regulated along with the up-regulation of those genes involved in glutamate pathway (Glu-P5CS-P5C/GSA-P5CR-Pro). Therefore, we concluded that the expression of AtOAT enhanced wheat abiotic tolerance via modifying the proline biosynthesis by up-regulating the expression of the proline biosynthesis-associated genes and down-regulating that of the proline catabolic gene under stresses condition.

Variable phenotypes of gyrate atrophy in siblings with a nonsense mutation in OAT gene.

Background: Gyrate Atrophy (GA) is a rare autosomal recessive disorder characterized by progressive chorioretinal degeneration. It is caused due to mutations in OAT gene that encodes a defective ornithine-δ-aminotransferase enzyme. We aim to identify the molecular cause of the disease and correlate it with the phenotype.Materials and Methods: Clinical, biochemical and genetic analyses were performed in siblings with GA.Case Description: A 10-year-old girl presented with impaired vision was clinically diagnosed to have peripheral chorioretinal degeneration in both eyes due to GA with vitreous hemorrhage in the right eye. Similar chorioretinal degeneration was observed in the patient's sibling, while parents were normal. Biochemical analysis of plasma by LC-MS/MS showed an elevated ornithine level of 892.8 µmol/L in the patient and 572.3 µmol/L in the sibling. Familial genetic screening by Sanger sequencing revealed a nonsense mutation in exon 11 of the OAT gene (c.1192C>T; p.Arg398Ter) in all the family members with a homozygous mutation in the patient and sibling, and heterozygous mutation in the parents. The patient was under follow-up with an arginine-restricted diet. At the last follow-up, the vitreous hemorrhage of right eye had resolved with an improvement in visual acuity and left eye remained stable with 6/12.Conclusion: Our patient is a rare case of gyrate atrophy presented with vitreous hemorrhage and nonsense OAT gene mutation, inherited in the autosomal recessive pattern. This report highlights the phenotypic variability among the siblings with the same mutation in OAT gene for the first time.

Deficit of human ornithine aminotransferase in gyrate atrophy: Molecular, cellular, and clinical aspects.

Gyrate Atrophy (GA) of the choroid and retina (MIM# 258870) is an autosomal recessive disorder due to mutations of the OAT gene encoding ornithine-delta-aminotransferase (OAT), associated with progressive retinal deterioration and blindness. The disease has a theoretical global incidence of approximately 1:1,500,000. OAT is mainly involved in ornithine catabolism in adults, thus explaining the hyperornithinemia as hallmark of the disease. Patients are treated with an arginine-restricted diet, to limit ornithine load, or the administration of Vitamin B6, a precursor of the OAT coenzyme pyridoxal phosphate. Although the clinical and genetic aspects of GA are known for many years, the enzymatic phenotype of pathogenic variants and their response to Vitamin B6, as well as the molecular mechanisms explaining retinal damage, are poorly clarified. Herein, we provide an overview of the current knowledge on the biochemical properties of human OAT and on the molecular, cellular, and clinical aspects of GA.

Pyrroline-5-carboxylate synthase senses cellular stress and modulates metabolism by regulating mitochondrial respiration.

Pyrroline-5-carboxylate synthase (P5CS) catalyzes the synthesis of pyrroline-5-carboxylate (P5C), a key precursor for the synthesis of proline and ornithine. P5CS malfunction leads to multiple human diseases; however, the molecular mechanism underlying these diseases is unknown. We found that P5CS localizes in mitochondria in rod- and ring-like patterns but diffuses inside the mitochondria upon cellular starvation or exposure to oxidizing agents. Some of the human disease-related mutant forms of P5CS also exhibit diffused distribution. Multimerization (but not the catalytic activity) of P5CS regulates its localization. P5CS mutant cells have a reduced proliferation rate and are sensitive to cellular stresses. Flies lacking P5CS have reduced eclosion rates. Lipid droplets accumulate in the eyes of the newly eclosed P5CS mutant flies, which degenerate with aging. The loss of P5CS in cells leads to abnormal purine metabolism and lipid-droplet accumulation. The reduced lipid-droplet consumption is likely due to decreased expression of the fatty acid transporter, CPT1, and few ß-oxidation-related genes following P5CS knockdown. Surprisingly, we found that P5CS is required for mitochondrial respiratory complex organization and that the respiration defects in P5CS knockout cells likely contribute to the metabolic defects in purine synthesis and lipid consumption. This study links amino acid synthesis with mitochondrial respiration and other key metabolic processes, whose imbalance might contribute to P5CS-related disease conditions.

First report of c.425-1G>A mutation in ornithine aminotransferase gene causing gyrate atrophy of the choroid and retina with hyperornithinemia.

BACKGROUND: Gyrate atrophy is a rare autosomal recessive inherited genetic disease. Progressive deterioration of peripheral night vision and blindness are the foremost clinical manifestations of the disease caused by mutations of ornithine aminotransferase gene. CASE: The presented case was an 18-year-old male referred for a progressive reduction of visual acuity, which started when the subject was 7 years old, blurred vision, and hypotonic muscles. OBSERVATIONS: The findings by liquid chromatography with tandem mass spectrometry and high-performance liquid chromatography methods exhibited a high level of ornithine: 248 µmol/L (reference range: 44-206 µmol/L) and 818 µmol/L (reference: 25-123 µmol/L), respectively. After genetic counseling and conducting further investigation, a novel mutation (c.425-1G>A) in ornithine aminotransferase gene was recognized through whole exome sequencing and the mutation was verified using Sanger sequencing method, which is associated with gyrate atrophy phenotype. CONCLUSION: The exact mechanism of chorioretinal atrophy in hyperornithinemia is not known but the increased ornithine level is the clinical manifestation of gyrate atrophy of choroid and retina, muscle weakness, moderate mental retardation, and low cerebral creatine. Pathogenic variant in the ornithine aminotransferase gene associated with gyrate atrophy, may be beneficial as a biomarker to initial diagnosis and treatment of gyrate atrophy disease.

A novel c.980C>G variant in OAT results in identifiable gyrate atrophy phenotype associated with retinal detachment in a young female.

Background: Gyrate atrophy of the choroid and retina (GA) is a rare autosomal recessive disorder characterized by nyctalopia, myopia, sharply demarcated expanding peripheral chorioretinal atrophic lesions, early cataract, progressive visual loss and hyperornithinemia. Only three cases of GA associated with rhegmatogenous retinal detachments (RRD) have been reported. The genotype-phenotype correlation of RRD in GA is limited by lack of genetic information in the previously reported cases. Here we report two young sisters with a characteristic GA phenotype associated with a novel variant in the ornithine aminotransferase gene (OAT), in whom one developed unilateral RRD at the age of 9 years.Materials and Methods: Retrospective report of two cases including genetic analysis and multimodal retinal imaging.Results: A 9-year-old Saudi girl presented with a funnel-shaped RRD, extensive proliferative vitreoretinopathy, peripheral choroidal detachment and neovascular glaucoma in her right eye. Fundus examination of her left eye showed an attached retina with sharply-demarcated peripheral chorioretinal atrophic patches suggestive of GA. Whole exome sequencing confirmed GA by revealing a homozygous c.980 C > G (p. Pro327Arg) variant in exon 8 of OAT. The RRD was inoperable. The chorioretinal lesions in the left eye enlarged slowly over 3 years of follow up. Examination of the proband's older sister revealed a similar but more advanced GA phenotype in both eyes.Conclusions: A characteristic GA phenotype associated with a novel variant in OAT is reported. This variant might be associated with childhood-onset RRD in the proband.

Directed Evolution of Ornithine Cyclodeaminase Using an EvolvR-Based Growth-Coupling Strategy for Efficient Biosynthesis of l-Proline.

l-Proline takes a significant role in the pharmaceutical and chemical industries as well as graziery. Typical biosynthesis of l-proline is from l-glutamate, involving three enzyme reactions as well as a spontaneous cyclization. Alternatively, l-proline can be also synthesized in l-ornithine and/or l-arginine producing strains by an ornithine aminotransferase (OCD). In this study, a strategy of directed evolution combining rare codon selection and pEvolvR was developed to screen OCD with high catalytic efficiency, improving l-proline production from l-arginine chassis cells. The mutations were generated by CRISPR-assisted DNA polymerases and were screened by growth-coupled rare codon selection system. OCDK205G/M86K/T162A from Pseudomonas putida was identified with 2.85-fold increase in catalytic efficiency for the synthesis of l-proline. Furthermore, we designed and optimized RBS for the BaargI and Ppocd coupling cascade using RedLibs, as well as sRNA inhibition of argF to moderate l-proline biosynthesis in l-arginine overproducing Corynebacterium crenatum. The strain PS6 with best performance reached 15.3 g/L l-proline in the shake flask and showed a titer of 38.4 g/L in a 5 L fermenter with relatively low concentration of residual l-ornithine and/or l-arginine.

Development of a Proline-Based Selection System for Reliable Genetic Engineering in Chinese Hamster Ovary Cells.

Chinese hamster ovary (CHO) cells are the superior host cell culture models used for the bioproduction of therapeutic proteins. One of the prerequisites for bioproduction using CHO cell lines is the need to generate stable CHO cell lines with optimal expression output. Antibiotic selection is commonly employed to isolate and select CHO cell lines with stable expression, despite its potential negative impact on cellular metabolism and expression level. Herein, we present a novel proline-based selection system for the isolation of stable CHO cell lines. The system exploits a dysfunctional proline metabolism pathway in CHO cells by using a pyrroline-5-carboxylate synthase gene as a selection marker, enabling selection to be made using proline-free media. The selection system was demonstrated by expressing green fluorescent protein (GFP) and a monoclonal antibody. When GFP was expressed, more than 90% of stable transfectants were enriched within 2 weeks of the selection period. When a monoclonal antibody was expressed, we achieved comparable titers (3.35 ± 0.47 µg/mL) with G418 and Zeocin-based selections (1.65 ± 0.46 and 2.25 ± 0.07 µg/mL, respectively). We further developed a proline-based coselection by using S. cerevisiae PRO1 and PRO2 genes as markers, which enables the generation of 99.5% double-transgenic cells. The proline-based selection expands available selection tools and provides an alternative to antibiotic-based selections in CHO cell line development.

Cloning and molecular characterization of Triticum aestivum ornithine amino transferase (TaOAT) encoding genes.

BACKGROUND: Ornithine aminotransferase (OAT, EC:2.6.1.13), alternatively known as ornithine delta aminotransferase (δOAT), is a pyridoxal phosphate (PLP)-dependent enzyme involved in the conversion of ornithine into glutamyl-5-semi-aldehyde (GSA) and vice versa. Up till now, there has been no study on OAT in wheat despite the success of its isolation from rice, maize, and sorghum. This study focuses on identification and molecular characterization of OAT in wheat. RESULTS: In total, three homeologous OAT genes in wheat genome were found on chromosome group 5, named as TaOAT-5AL, TaOAT-5BL, and TaOAT-5DL. Sequence alignment between gDNA and its corresponding cDNA obtained a total of ten exons and nine introns. A phylogenetic tree was constructed and results indicated that OATs shared highly conserved domains between monocots and eudicots, which was further illustrated by using WebLogo to generate a sequence logo. Further subcellular localization analysis indicated that they functioned in mitochondria. Protein-protein interactions supported their role in proline biosynthesis through interactions with genes, such as delta 1-pyrroline-5-carboxylate synthetase (P5CS) and pyrroline-5-carboxylate reductase (P5CR), involved in the proline metabolic pathway. Promoter analysis exposed the presence of several stress responsive elements, implying their involvement in stress regulation. Expression profiling illustrated that TaOAT was highly induced in the wheat plants exposed to drought or salt stress condition. Upregulated expression of TaOATs was observed in stamens and at the heading stage. A potential role of TaOAT genes during floret development was also revealed. Furthermore, the transgenic plants overexpressing TaOAT showed enhanced tolerance to drought stress by increasing proline accumulation. In addition, salt tolerance of the transgenic plants was also enhanced. CONCLUSION: TaOATs genes were involved in proline synthesis and nitrogen remobilization because they interacted with genes related to proline biosynthesis enzymes and arginine catabolism. In addition, TaOAT genes had a role in abiotic stress tolerance and a potential role in floret development. The results of this study may propose future research in the improvement of wheat resistance to abiotic stresses.

The proline synthesis enzyme P5CS forms cytoophidia in Drosophila.

Compartmentation of enzymes via filamentation has arisen as a mechanism for the regulation of metabolism. In 2010, three groups independently reported that CTP synthase (CTPS) can assemble into a filamentous structure termed the cytoophidium. In searching for CTPS-interacting proteins, here we perform a yeast two-hybrid screening of Drosophila proteins and identify a putative CTPS-interacting protein, △1-pyrroline-5-carboxylate synthase (P5CS). Using the Drosophila follicle cell as the in vivo model, we confirm that P5CS forms cytoophidia, which are associated with CTPS cytoophidia. Overexpression of P5CS increases the length of CTPS cytoophidia. Conversely, filamentation of CTPS affects the morphology of P5CS cytoophidia. Finally, in vitro analyses confirm the filament-forming property of P5CS. Our work links CTPS with P5CS, two enzymes involved in the rate-limiting steps in pyrimidine and proline biosynthesis, respectively.