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    Differential expression of soluble pyrophosphatase isoforms in Arabidopsis upon external stimuli
    (TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2015) Oeztuerk, Zahide Neslihan; Greiner, Steffen; Rausch, Thomas
    In plants, pyrophosphate (PPi), generated in a wide range of reversible anabolic reactions, is hydrolyzed by pyrophosphatases. The presence of tonoplast-and Golgi-integral H+-translocating pyrophosphatases in plants led to the conclusion that plant cytosol has no soluble pyrophosphatase activity. However, the Arabidopsis thaliana (L.) Heynh. genome also encodes five soluble pyrophosphatase isoforms (PPas). There are almost no data in the literature on their redundancy in plant metabolism; therefore, we performed expression analyses of A. thaliana soluble pyrophosphatase isoforms in response to external stimuli including carbohydrate status, hormone action, and stress exposure. The results revealed pronounced specificity for each isoform. Interestingly, one isoform (PPa3; At2g46860) was specifically induced during seedling etiolation, and in the presence of the nonmetabolizable sugar 3-O-methylglucose. Based on quantitative PCR analyses, PPa1 (At1g01050) and PPa4 (At3g53620) appeared to be regulated by sugars. Quantitative PCR analyses indicated isoform-and tissue-dependent responses of PPa isoforms to ABA, salt, and cold stresses. PPa2 (At2g18230) and PPa5 (At4g01480) responded differentially to salinity, cold treatment, and ABA. We conclude that plant cytosolic pyrophosphatases perform multiple, so far overlooked functions during plant development and stress exposure.
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    Subcellular localization and developmental regulation of cytosolic, soluble pyrophosphatase isoforms in Arabidopsis thaliana
    (TUBITAK SCIENTIFIC & TECHNICAL RESEARCH COUNCIL TURKEY, 2014) Ozturk, Zahide Neslihan; Greiner, Steffen; Rausch, Thomas
    Pyrophosphate (PPi) is the by-product of several reversible key reactions of primary metabolism. Thus, generated PPi should be removed by hydrolysis via pyrophosphatases to prevent accumulation and to drive anabolism. In plastids, a plastidic, soluble pyrophosphatase splits PPi released by ADPG pyrophosphorylase. The cytosolic PPi pool is believed to be hydrolyzed by tonoplast- and/or Golgi-integral H+-translocating pyrophosphatases. The Arabidopsis thaliana (L.) Heynh. genome encodes 6 soluble pyrophosphatase isoforms (PPas), 1 of which was shown to be localized in plastids. The remaining 5 of those PPas (PPas 1-5) are more similar to each other with highly conserved protein sequences. They all lack known targeting sequences and are thought to reside in the cytosol. To address their role and redundancy in plants, we performed (i) subcellular targeting of C-terminal PPa:EGFP fusions, (ii) analysis of transgenic promoter beta-glucuronidase (GUS) lines to depict differential expression during plant development, and (iii) transcript quantification via real-time PCR to corroborate promoter-GUS data. The results revealed pronounced tissue specificity and developmental regulation for each PPa isoform, but also partial redundancy with coexpression of several PPa isoforms in all plant tissues.