TOR kinase controls shoot development by translational regulation of cytokinin catabolic enzymes
Plants continuously adjust their developmental program including organ initiation and growth in accordance with endogenous and environmental signals. This plasticity requires that a diversity of signaling pathways acts in concert to modulate stem cell activity. We have shown previously that the TOR kinase network integrates metabolic- and light signals and controls expression of WUSCHEL, a transcriptional master regulator of stem cells in the shoot apical meristem. However, the mechanism linking TOR activity with the WUSCHEL promoter remained unresolved. Here we demonstrate that TOR regulates the accumulation of trans-zeatin, the cytokinin species mainly responsible for shoot development. Importantly, we identify translational repression of RNAs encoding cytokinin degrading CYTOKININ OXIDASES/DEHYDROGENASE enzymes by TOR as an underlying mechanism. Employing this system, plants can quickly adjust stem cell activity and developmental programs in response to changes in their environment.