Roots and nodules of the actinorhizal plants Alnus glutinosa and Datisca glomerata, as well as Frankia alni ACN14a grown in minimal and ammonium supplemented media, were analyzed for amino acid profiles. To analyze nitrogen and carbon metabolism, the transcriptome in nodules of the microsymbiont of D. glomerata, Frankia datiscae Dg1, was sequenced and compared with transcriptome data from symbiotic F. alni ACN14a (Alloisio et al. 2011). The amino acid profile of A. glutinosa roots suggests that Citrulline, Asparagine and Glutamine are transported in the xylem. Moreover, the comparatively high concentration of γ-aminobutyric acid in A. glutinosa roots suggest that this compound has a function in plant nitrogen metabolism. γ-aminobutyric acid could, as was suggested for the legume symbiosis, act as a signal factor for the plant nitrogen status to symbiotic Frankia. It could also be imported by the bacteria as a carbon and nitrogen source. Moreover, the expression of the gene for the enzyme catalyzing β-Alanine synthesis was elevated in both Frankia strains in symbiosis. Elevated concentrations of β-Alanine in nodules of D. glomerata and A. glutinosa compared to roots suggest that β-Alanine is produced by the bacteria in large amounts, possibly as a storage compound for Coenzyme A production.