TOR kinase controls shoot development by translational regulation of cytokinin catabolic enzymes

Plants continuously adjust the rate at which new organs are produced in accordance with endogenous and environmental signals. Therefore, a multitude of signaling pathways converge to modulate stem cell activity. We have shown previously, that the TOR kinase network integrates metabolic- and light signals to control expression of WUSCHEL, a transcriptional master regulator of stem cells in the shoot apical meristem (SAM). However, the link between TOR and WUS promoter activity remained unresolved. Here we demonstrate that TOR controls trans-Zeatin abundance, the cytokinin derivative that is the main driver of shoot development. Moreover, we identify TOR mediated translational control of cytokinin degrading CYTOKININ OXIDASES/DEHYDROGENASE (CKX) enzymes as the underlying mechanism, which allows the plant to adjust the stem cell signaling environment and growth pattern within minutes after changes in environmental parameters.