Adequate intake of dietary essential amino acids (eAAs) is vital for protein synthesis and metabolism. Any single eAA deprivation is sufficient to increase protein intake in Drosophila melanogaster. How such nutritional "needs" are transformed into behavioral "wants" remains poorly understood. We derived transcriptomes from the heads of flies deprived of individual eAAs to identify mechanisms by which this is achieved. While specific eAA deprivations have unique effects on gene expression, a large set of changes is shared across deprivations. Namely, we show that Or92a, which is essential for the exploitation of yeast, the main protein source for flies, is upregulated upon eAA deprivation. Additionally, Ir76a upregulation is crucial for feeding on commensal bacteria that ameliorate the fitness of eAA-deprived flies. Our work uncovers common and unique transcriptional changes induced by individual eAA deprivations in animals and reveals novel mechanisms underlying the organism's behavioral and physiological adaptation to eAA challenges.