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Plant Physiology Preview Published on April 25, 2008; 10.1104/pp.108.120014
Received March 28, 2008 pur4 mutations are lethal to the male, but not the female gametophyte and affect sporophyte development in Arabidopsis
Station de Genetique et d'Amelioration des Plantes, Institut Jean-Pierre Bourgin, INRA UR254, centre de Versailles, route de Saint Cyr, 78026 Versailles cedex, France * Corresponding author; email: budar{at}versailles.inra.fr.
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 PUR4 gene (At1g74260) that encodes formylglycinamidine ribonucleotide synthase (FGAMS; 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 (GFP) in Arabidopsis plantlets showed that the FGAMS 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.
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