title: The folylpolyglutamate synthetase plastidial isoform is required for postembryonic root development in Arabidopsis.
abstract: A recessive Arabidopsis (Arabidopsis thaliana) mutant with short primary roots and root hairs was identified from a forward genetic screen. The disrupted gene in the mutant encoded the plastidial isoform of folylpolyglutamate synthetase (FPGS), previously designated as AtDFB, an enzyme that catalyzes the addition of glutamate residues to the folate molecule to form folylpolyglutamates. The short primary root of atdfb was associated with a disorganized quiescent center, dissipated auxin gradient in the root cap, bundled actin cytoskeleton, and reduced cell division and expansion. The accumulation of monoglutamylated forms of some folate classes in atdfb was consistent with impaired FPGS function. The observed cellular defects in roots of atdfb underscore the essential role of folylpolyglutamates in the highly compartmentalized one-carbon transfer reactions (C1 metabolism) that lead to the biosynthesis of compounds required for metabolically active cells found in the growing root apex. Indeed, metabolic profiling uncovered a depletion of several amino acids and nucleotides in atdfb indicative of broad alterations in metabolism. Methionine and purines, which are synthesized de novo in plastids via C1 enzymatic reactions, were particularly depleted. The root growth and quiescent center defects of atdfb were rescued by exogenous application of 5-formyl-tetrahydrofolate, a stable folate that was readily converted to metabolically active folates. Collectively, our results indicate that AtDFB is the predominant FPGS isoform that generates polyglutamylated folate cofactors to support C1 metabolism required for meristem maintenance and cell expansion during postembryonic root development in Arabidopsis.
authors.affiliation: Plant Biology Division, Samuel Roberts Noble Foundation, Ardmore, Oklahoma 73401, USA.
authors.forename: Avinash C
authors.initials: AC
authors.lastname: Srivastava
authors.forename: Perla A
authors.initials: PA
authors.lastname: Ramos-Parra
authors.forename: Mohamed
authors.initials: M
authors.lastname: Bedair
authors.forename: Ana L
authors.initials: AL
authors.lastname: Robledo-Hernández
authors.forename: Yuhong
authors.initials: Y
authors.lastname: Tang
authors.forename: Lloyd W
authors.initials: LW
authors.lastname: Sumner
authors.forename: Rocío I
authors.initials: RI
authors.lastname: Díaz de la Garza
authors.forename: Elison B
authors.initials: EB
authors.lastname: Blancaflor
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002244:Carbon / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D018745:Genome, Plant / Q000235:genetics; D018698:Glutamic Acid / Q000378:metabolism; D006151:Guanosine / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D055442:Metabolome / Q000187:drug effects; D008715:Methionine / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010453:Peptide Synthases / Q000378:metabolism*; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development* / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D018087:Plastids / Q000201:enzymology*; D036226:Seedlings / Q000187:drug effects / Q000378:metabolism; D013763:Tetrahydrofolates / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D007527:Isoenzymes; D013763:Tetrahydrofolates; D006151:Guanosine; D018698:Glutamic Acid; C030371:5,6,7,8-tetrahydrofolic acid; D002244:Carbon; D008715:Methionine; D010453:Peptide Synthases; C023103:folylpolyglutamate synthetase