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On the Cover: NADH-Glu synthase (GOGAT), in concert with Gln synthase, catalyzes the assimilation of symbiotically fixed nitrogen into amino acids in legume root nodules. Trepp et al. (pp. 817-828) evaluated the genetic and biochemical regulation of NADH-GOGAT in alfalfa through analysis of the 5-upstream region of the gene, in situ hybridization, and immunocytochemistry. In infected cells of root nodules, immunoreactive staining with NADH-GOGAT antibodies was most intense at the periphery in areas corresponding to the location of amyloplasts. Immunogold labeling confirmed that NADH-GOGAT was localized predominantly in amyloplasts of infected cells. In an accompanying report (pp. 829-837), Trepp et al. show that NADH-GOGAT transcripts were localized via in situ hybridization. The image shows that NADH-GOGAT mRNA in a 19-d-old nodule was found in infected cells throughout the nitrogen-fixing zone. Analysis of older nodules revealed that NADH-GOGAT mRNA was detected only in the youngest infected cells coincident with the expression of bacterial nitrogenase. Transcript analysis and subcellular localization studies demonstrate that NADH-GOGAT in amyloplasts of the infected cells of legume nodules plays a critical role in the assimilation of fixed nitrogen into Glu and Asp.