Abstract
Cytokinins are N6-prenylated adenine derivatives such as isopentenyladenine (iP) and trans-zeatin (tZ). In the biosynthesis pathway, nucleotide form is initially produced as a cytokinin precursor and converted to the nucleobase, the active form. It is expected that two pathways are involved in producing active cytokinin: the two-step activation pathway and the direct activation pathway. In the fomer, cytokinin nucleotides are successively converted to the nucleosides and nucleobases. In the latter, LOG directly produces cytokinin nucleobase from the nucleotide. However, it is not clear whether there is a functional differentiation between these two activating pathways. To assess which pathway mainly contributes to cytokinin activation, cytokinin metabolic fluxes were monitored by using stable isotope. Our analyses with LOG mutants suggest that direct pathway meditated by LOG mainly contributes to produce bioactive cytokinin in Arabidopsis seeding.
