Primary Metabolism of Apple Fruit During Development As Affected by Carbon and Nitrogen Supply

Metabolite concentration and composition in apple fruit at harvest, which largely defines fruit quality, is determined through a complex interplay between genotype, environmental factors, and orchard management practices during fruit development.  Primary metabolites, including sugars, sugar alcohols, organic acids, and amino acids, not only determine the sweetness and acidity of the fruit, but they also provide the background in which aroma compounds are sensed and serve as precursors for aroma compounds. Recent advances in metabolite profiling techniques, combined with assay of the transcript level and activity of the key enzymes involved in primary metabolism, allowed us to gain a more comprehensive picture of the primary metabolism in apple fruit during development. This presentation will focus on some of our work on apple fruit in transgenic apple trees with decreased sorbitol synthesis and those grown under different nitrogen supply to demonstrate how the metabolism of carbohydrates, organic acids, nitrogen, and amino acids are integrated during fruit development, resulting in changes in the concentration and composition of metabolites at harvest.