Cytosolic HPPK/DHPS from Arabidopsis thaliana: A specific role in stress response. - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Journal of Biological Chemistry Année : 2007

Cytosolic HPPK/DHPS from Arabidopsis thaliana: A specific role in stress response.

Résumé

In plants, 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase/7,8- dihydropteroate synthase (mitHPPK/DHPS) is a bifunctional mitochondrial enzyme, which catalyses the first two consecutive steps of tetrahydrofolate biosynthesis. Mining the Arabidopsis genome database has revealed a second gene encoding a protein that lacks a potential transit peptide, suggesting a cytosolic localization of the isoenzyme (cytHPPK/DHPS). When the N-terminal part of the cytHPPK/DHPS was fused to GFP, the fusion protein appeared only in the cytosol, confirming the above prediction. Functionality of cytHPPK/DHPS was addressed by two parallel approaches: first, the cytHPPK/DHPS was able to rescue yeast mutants lacking corresponding activities; second, recombinant cytHPPK/DHPS expressed and purified from E. coli displayed both HPPK and DHPS activities in vitro. In contrast to mitHPPK/DHPS, which was ubiquitously expressed, the cytHPPK/DHPS gene was exclusively expressed in reproductive tissue, more precisely in developing seeds as revealed by histochemical analysis of a transgenic cytHPPK/DHPS promoter-GUS line. In addition, it was observed that expression of cytHPPK/DHPS mRNA was induced by salt stress, suggesting a potential role of the enzyme in stress response. This was supported by the phenotype of a T-DNA insertion mutant in the cytHPPK/DHPS gene, resulting in lower germination rates as compared to the wild type upon application of oxidative and osmotic stress.
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hal-00139373 , version 1 (31-05-2020)

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Sergei Storozhenko, Oscar Navarette, Stéphane Ravanel, Veerle de Brouwer, Peter Chaerle, et al.. Cytosolic HPPK/DHPS from Arabidopsis thaliana: A specific role in stress response.. Journal of Biological Chemistry, 2007, Published online, ⟨10.1074/jbc.M701158200⟩. ⟨hal-00139373⟩
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