The symbiotic interaction between legumes and rhizobia results in root nodules with nitrogen-fixing bacteroids. Throughout the lifespan of the nodules, the exchange of C-sources and N-compounds between the host plant and the bacteria is tightly balanced. Sucrose plays a major role in the provision of C-skeletons and energy to the bacteroids. Transcription of MtATB2, encoding a bZIP transcription factor, is shown to be regulated by sucrose and is enhanced during nodule senescence. Transcripts occur in the nodule apex and in the vascular tissue of nodules and roots. Ectopic expression of the gene diminished nodule formation and affected root growth. Presumably, MtATB2 controls processes that are under sucrose homeostasis and are important for nodule and root growth.