Structure and function of nucleoside hydrolases from Physcomitrella patens and maize catalyzing the hydrolysis of purine, pyrimidine, and cytokinin ribosides.

We present a comprehensive characterization of the nucleoside N-ribohydrolase (NRH) family in two model plants, Physcomitrella patens (PpNRH) and maize (Zea mays; ZmNRH), using in vitro and in planta approaches. We identified two NRH subclasses in the plant kingdom; one preferentially targets the purine ribosides inosine and xanthosine, while the other is more active toward uridine and xanthosine. Both subclasses can hydrolyze plant hormones such as cytokinin ribosides.

Adenosine kinase contributes to cytokinin interconversion in Arabidopsis.

Purine salvage enzymes have been implicated, but not proven, to be involved in the interconversion of cytokinin (CK) bases, ribosides, and nucleotides. Here, we use Arabidopsis (Arabidopsis thaliana) lines silenced in adenosine kinase (ADK) expression to understand the contributions of this enzyme activity to in vivo CK metabolism. Both small interfering RNA- and artificial microRNA-mediated silencing of ADK led to impaired root growth, small, crinkled rosette leaves, and reduced apical dominance.

Cytokinins in the bryophyte Physcomitrella patens: analyses of activity, distribution, and cytokinin oxidase/dehydrogenase overexpression reveal the role of extracellular cytokinins.

Ultra-performance liquid chromatography-tandem mass spectrometry was used to establish the cytokinin profile of the bryophyte Physcomitrella patens (Hedw.) B.S.