RNA polymerase I (Pol I)-dependent rDNA transcription is a key regulatory step in ribosome biogenesis, a major energy consuming process required for cell growth and division. Not surprisingly, cells develop a complex and integrated growth factor, nutrient and energy sensing network which converges to control rDNA transcription. Much less is known about the regulation of ribosome biogenesis in response to amino acid levels, although very early reports indicated rRNA synthesis was down regulated in response to amino acid starvation. Here we demonstrate that regulation of rDNA transcription is a critical and immediate cellular response to altered amino acid levels. Amino acids regulate rRNA synthesis at multiple levels, including transcription initiation and elongation as well as rRNA processing. Upon amino acid withdrawal, post-initiation steps are more rapidly impaired followed by repression of Pol I loading onto the rDNA. Re-addition of amino acids into amino acids and serum starved cells results in a rapid and potent activation of rDNA transcription, which is dependent on mTORC1 signalling and mediated through S6K1 activity. Despite no AKT activation upon amino acid stimulation, AKT-dependent, but mTORC1-indepent signaling is required to maintain basal rRNA synthesis. Consequently, in the absence of AKT activity, amino acid-activated mTORC1 signalling is not sufficient to drive rDNA transcription. In addition, MYC is also required for response of rDNA transcription to amino acids through a parallel pathway. Furthermore, amino acid availability affects the response of rDNA transcription to growth factor. In the absence of amino acid, signaling downstreatm of growth factor is incapable of stimulating rDNA transcription efficiently, effects that correlated with decreased mTORC1 signalling and reduced Pol I loading onto the transcribe regions close to the 3’ end, suggesting amino acid signaling primarily impacts on the post-initiation events of rDNA transcription in response to growth factor. Therefore, cooperation of growth factor signaling and amino acid signaling is required for optimal rDNA transcription. Finally, consistent with the critical role of glutamine in cell growth and metabolism as well as modulation of mTORC1 activity, we showed that amino acid regulated Pol I transcription is mediated in part by glutaminolysis. Nevertheless, no effect on rDNA transcription was observed upon re-addition of leucine and glutamine into amino acid starved cells, implicating that a sufficient level of other amino acids are required. This study thus provides a fundamental insight into nutrient control of ribosome biogenesis and cell growth.