Journal Article

Folylpolyglutamate Synthetase Plastidial Isoform Is Required for Postembryonic Root Development in Arabidopsis

Ramos-Parra, Perla A, Díaz de la Garza, Rocío I, Tang, Yuhong, Blancaflor, Elison B, Srivastava, Avinash C, Sumner, Lloyd W, Bedair, Mohamed, Robledo-Hernández, Ana L

2011

Overview

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.

• Publisher: American Society of Plant Biologists
• Subject: Arabidopsis / Arabidopsis - cytology / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis - growth & development / Arabidopsis Proteins / Arabidopsis Proteins - metabolism / Arabidopsis thaliana / auxins / Biological and medical sciences / Biosynthesis / Carbon / Carbon - metabolism / cell division / Cell Division - drug effects / Cell Proliferation / Cell Proliferation - drug effects / Cellular metabolism / cytology / DEVELOPMENT AND HORMONE ACTION / Developmental biology / drug effects / enzymatic reactions / enzymes / enzymology / Epidermal cells / folic acid / Fundamental and applied biological sciences. Psychology / genes / genetics / Genome, Plant / Genome, Plant - genetics / glutamates / Glutamic Acid / Glutamic Acid - metabolism / growth & development / Guanosine / Guanosine - pharmacology / Indoleacetic Acids / Indoleacetic Acids - metabolism / Isoenzymes / Isoenzymes - metabolism / metabolism / Metabolome / Metabolome - drug effects / metabolomics / methionine / Methionine - pharmacology / microfilaments / mutants / Mutation / Mutation - genetics / nucleotides / Peptide Synthases / Peptide Synthases - metabolism / pharmacology / Phenotype / Plant cells / Plant physiology and development / Plant Roots / Plant Roots - drug effects / Plant Roots - enzymology / Plant Roots - growth & development / Plant Roots - metabolism / Plant Shoots / Plant Shoots - drug effects / Plant Shoots - growth & development / Plant Shoots - metabolism / Plants / Plastids / Plastids - enzymology / Protein isoforms / root cap / Root growth / root hairs / Seedlings / Seedlings - drug effects / Seedlings - metabolism / Tetrahydrofolates / Tetrahydrofolates - metabolism