Abstract
Cytokinins play crucial roles in diverse aspects of plant growth and development. In the biosynthesis pathway, nucleotide form is initially produced as a cytokinin precursor. It is expected that two pathways are involved in producing active form from the nucleotide: two-step activation pathway and direct activation pathway. The direct pathway mediates production of the active nucleobases from the nucleotides. LONELY GUY (LOG) was previously identified as a cytokinin-activating enzyme that works in the direct activation pathway in rice shoot meristems. However, it is not clear whether there is a functional differentiation between these two activating pathways. In Arabidopsis, we have identified seven LOG-like genes (AtLOG1-5, 7, 8), and analyzed the phenotypes of various combinations of the multiple knock-out mutants. Our results strongly suggested that the direct activation pathway plays a crucial role in cytokinin activation.
