pur4 Mutations Are Lethal to the Male, But Not the Female, Gametophyte and Affect Sporophyte Development in Arabidopsis

Abstract

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 pur4-2/1 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.Purine nucleotides are major metabolites in living cells, at the crossroads of energy metabolism and the synthesis of essential cofactors and nucleic acids. In plants, purine molecules are also precursors for cytokinin metabolism and for the production of secondary metabolites such as ureides and alkaloids. Purine metabolism is complex, comprising a de novo synthesis pathway, which produces IMP, the direct precursor for AMP and GMP, from simple molecules; a salvage pathway allowing the recycling of purine rings at lower energetic cost; and a degradation pathway,

Assembly of an Interactive Correlation Network for the Arabidopsis Genome Using a Novel Heuristic Clustering Algorithm

“…These results illustrate how a coherent and easy-to-navigate data visualization scheme, such as the AraGenNet, can predict biologically meaningful relationships. Recently, the pollen-deficient mutant corresponding to the gene At1g74260 was confirmed by another study (Berthomé et al, 2008).…”

Mutations defective in ribonucleotide reductase activity interfere with pollen plastid DNA degradation mediated by DPD1 exonuclease

“…Similar to dpd2, a T-DNA insertion mutant of formylglycinamidine ribonucleotide synthase (PUR4), which is defective in purine synthesis, also exhibits defective pollen development, such as pollen abortion, abnormal cytoplasm staining and impaired pollen mitosis (Berthomé et al, 2008). However, the presence of the dpd phenotype was not described in phenotypic analyses of pur4 by Berthomé et al (2008). Taken together, we suggest that maintenance of a balanced nucleotide pool by RNR is vital for pollen to develop normally.…”

“…, 2008). However, the presence of the dpd phenotype was not described in phenotypic analyses of pur4 by Berthomé et al. (2008).…”

“…Although pollen mitosis is not affected in dpd2 (as shown by detection of the trinucleate structure), a proportion of dpd2 pollen grains showed morphological abnormalities in addition to decreased germination and viability rates (Figure 2). Similar to dpd2, a T-DNA insertion mutant of formylglycinamidine ribonucleotide synthase (PUR4), which is defective in purine synthesis, also exhibits defective pollen development, such as pollen abortion, abnormal cytoplasm staining and impaired pollen mitosis (Berthomé et al, 2008). However, the presence of the dpd phenotype was not described in phenotypic analyses of pur4 by Berthomé et al (2008).…”

Functional characterization of Arabidopsis thaliana isopropylmalate dehydrogenases reveals their important roles in gametophyte development

“…, 2008). Recently, it has been shown that a formylglycinamidine ribonucleotide synthase mutant ( pur4 ), defective in de novo purine biosynthesis, compromised male gametophyte development and to a smaller extent female gametophyte development (Berthome et al. , 2008).…”