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CELL BIOLOGY AND SIGNAL TRANSDUCTION

pur4 Mutations Are Lethal to the Male, But Not the Female, Gametophyte and Affect Sporophyte Development in Arabidopsis^[C],[W]

Station de Génétique et d'Amélioration des Plantes, Institut Jean-Pierre Bourgin, INRA UR254, 78026 Versailles cedex, France

Purine metabolism is crucial in living cells and involves three complex pathways in plants: the de novo synthesis, the salvage, and the degradation pathways. The relative importance of each pathway in plant development and reproduction, however, is still unclear. We identified two T-DNA insertions in the Arabidopsis (Arabidopsis thaliana) PUR4 gene (At1g74260) that encodes formylglycinamidine ribonucleotide synthase (EC 6.3.5.3), the fourth enzyme in the de novo purine biosynthesis pathway. The mutated alleles were never transmitted through the pollen of heterozygous plants but could be inherited through the female gametophyte, indicating that de novo purine synthesis is specifically necessary for pollen development. Because the pur4 mutations were lethal to the male gametophyte, homozygous pur4 plants could not be obtained. However, the reproductive phenotype of hetererozygous plants carrying the pur4-2 mutated allele was more severe than that carrying the pur4-1 mutated allele, and pur4-2/+ plants showed slightly delayed early development. We showed that the pur4-2 allele produces an antisense transcript and that the amount of PUR4 mRNA is reduced in these plants. Transient expression of a translational fusion with the green fluorescent protein in Arabidopsis plantlets showed that the formylglycinamidine ribonucleotide synthase protein is dually targeted to chloroplast and mitochondria, suggesting that at least some steps of the de novo purine biosynthesis pathway can take place in both organelles in Arabidopsis, a dual location previously thought to be a peculiarity of ureide-forming tropical legumes.

² Present address: Unité de Recherche Amélioration, Génétique et Physiologie Forestières, INRA, Avenue de la Pomme de Pin, Ardon-BP 20619, 45166 Olivet cedex, France.

³ Present address: Laboratoire de Reproduction et du Développement des Plantes, Ecole Normale Supérieure de Lyon, UMR 5667, INRA, ENS Lyon UCB Lyon, 46 allée d'Italie, 69364 Lyon cedex 07, France.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Richard Berthomé (berthome{at}evry.inra.fr).

^[C] Some figures in this article are displayed in color online but in black and white in the print edition.

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.120014

^* Corresponding author; e-mail budar{at}versailles.inra.fr.

Received March 28, 2008; accepted April 22, 2008; published April 25, 2008.