Analysis of the expression of the entire M. truncatula GS gene family during seed development. Seeds were collected at 3, 6, 10, 14, 20, 24 and 36 days after pollination. A. Quantification of MtGS1a, MtGS1b, MtGS2a and MtGS2b transcripts by qRT-PCR. GS transcript abundance was normalized to that of the housekeeping gene MtElf1-α. B. Western blot analysis of GS polypeptides using either an anti-Glnγ antibody recognizing both the cytosolic (GS1) and plastid-located (GS2) polypeptides  or a specific anti-GS2 antibody. Equal amount of protein (30 μg) were loaded on each lane. C. Quantification of GS activity on soluble protein extracts. Results are representative of three biological replicates.