Applying high throughput techniques in the study of adenosine kinase in plant metabolism and development.

Adenosine kinase (ADK, EC 2.7.1.20) is a purine salvage enzyme, which phosphorylates adenosine (Ado) to AMP. It may also contribute to the interconversion of cytokinin ribosides and nucleotides. Recent microarray analyses have provided new insights into the impact of ADK activity towards plant metabolism and development. The majority of these findings reflect ADK's role in the metabolism of Ado produced from transmethylation reactions in addition to providing necessary nucleotides for the synthesis of nucleic acids and nucleotide cofactors. As such, ADK was found to increase during events associated with high transmethylation activity, such as cell wall synthesis and seed filling. Differences between plant organs were also detected, with ADK transcript levels found highest in siliques and roots and lowest in callus, leaves and buds. Transcript profiling of Arabidopsis expression using microarrays, reveals a predominance of ADK1 expression relative to that of ADK2. In the majority of the studies, the isoforms appeared to behave in a similar pattern of expression, with the exception being microgametogenesis where ADK1 was up-regulated when ADK2 was not. What specialized function the ADK1 could be providing to these cells during development and whether or not this is occurring in other biochemical processes has yet to be determined.