The perception of nutrient and energy levels inside and outside the cell is crucial to adjust growth and metabolism to available resources. The signaling pathways centered on the conserved TOR and SnRK1/Snf1/AMPK kinases have crucial and numerous roles in nutrient and energy sensing and in translating this information into metabolic and developmental adaptations. In plants evidence is mounting that, like in other eukaryotes, these signaling pathways have pivotal and antagonistic roles in connecting external or intracellular cues to many biological processes, including ribosome biogenesis, regulation of translation, cell division, accumulation of reserves and autophagy. Data on the plant TOR pathway have been hitherto rather scarce but recent findings have shed new light on its roles in plants. Moreover, the distinctive energy metabolism of photosynthetic organisms may reveal new features of these ancestral eukaryotic signaling elements.
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