Section: New Results

Exploration of the genetic network of Buchnera aphidicola

Aphids are important agricultural pests which can grow and reproduce thanks to their intimate symbiosis with the $\gamma$-proteobacterium Buchnera aphidicola that furnishes them with essential amino acids lacking in their phloem sap diet. We investigated how B. aphidicola, with its reduced genome containing very few transcriptional regulators, responds to variations in the metabolic requirements of its host by concentrating attention on the leucine metabolic pathway [23] . We showed that leucine is a limiting factor for aphid growth and displays a stimulatory feeding effect. Our metabolic analyses demonstrated that symbiotic aphids are able to respond to leucine starvation or excess by modulating the neosynthesis of this amino acid. Taken together, our data showed that the response of B. aphidicola to the leucine demand of its host is multimodal and dynamically regulated, providing new insights concerning the genetic regulation capabilities of this bacterium in relation to its symbiotic functions.