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Arabidopsis thaliana nucleosidase mutants provide new insights into nucleoside degradation
Article first published online: 20 MAY 2011
© 2011 The Authors. New Phytologist © 2011 New Phytologist Trust
Volume 191, Issue 2, pages 349–359, July 2011
How to Cite
Riegler, H., Geserick, C. and Zrenner, R. (2011), Arabidopsis thaliana nucleosidase mutants provide new insights into nucleoside degradation. New Phytologist, 191: 349–359. doi: 10.1111/j.1469-8137.2011.03711.x
- Issue published online: 29 JUN 2011
- Article first published online: 20 MAY 2011
- Received: 22 December 2010, Accepted: 25 February 2011
- Arabidopsis thaliana mutant;
- nucleoside degradation;
- nucleotide metabolism;
- uridine nucleosidase;
- xanthosine nucleosidase
- •A central step in nucleoside and nucleobase salvage pathways is the hydrolysis of nucleosides to their respective nucleobases. In plants this is solely accomplished by nucleosidases (EC 3.2.2.x).
- •To elucidate the importance of nucleosidases for nucleoside degradation, general metabolism, and plant growth, thorough phenotypic and biochemical analyses were performed using Arabidopsis thaliana T-DNA insertion mutants lacking expression of the previously identified genes annotated as uridine ribohydrolases (URH1 and URH2).
- •Comprehensive functional analyses of single and double mutants demonstrated that both isoforms are unimportant for seedling establishment and plant growth, while one participates in uridine degradation. Rather unexpectedly, nucleoside and nucleotide profiling and nucleosidase activity screening of soluble crude extracts revealed a deficiency of xanthosine and inosine hydrolysis in the single mutants, with substantial accumulation of xanthosine in one of them. Mixing of the two mutant extracts, and by in vitro activity reconstitution using a mixture of recombinant URH1 and URH2 proteins, both restored activity, thus providing biochemical evidence that at least these two isoforms are needed for inosine and xanthosine hydrolysis.
- •This mutant study demonstrates the utility of in vivo systems for the examination of metabolic activities, with the discovery of the new substrate xanthosine and elucidation of a mechanism for expanding the nucleosidase substrate spectrum.