Antisense-inhibition of ADP-glucose pyrophosphorylase in developing seeds of Vicia narbonensis moderately decreases starch but increases protein content and affects seed maturation

The small subunit of a Vicia faba ADP-glucose pyrophosphorylase (AGP) cDNA was expressed in antisense orientation in Vicia narbonensis under the contr ol of the seed-specific legumin B4 promoter. From several independent trans genic lines both ADP-glucose pyrophosphorylase AGP-mRNA and AGP enzyme acti vity were reduced by up to 95% in the cotyledons during the mid- to late-ma turation phase. Starch was moderately decreased and sucrose was increased. In two of three lines, transcripts encoding the large subunit of AGP and th e storage protein vicilin were increased, whereas legumin B-mRNA was decrea sed. Transcripts of other storage-associated genes were not altered. The co tyledons contained more protein and total nitrogen. Despite the reduction i n starch, total carbon was not decreased and dry weight was unchanged. Comp ared to the wild type, transgenic seeds contained more water and accumulate d dry weight during a longer period, and therefore had a prolonged seed-fil ling period. Transgenic cotyledon cells of comparable age to the wild type were more highly vacuolated and contained smaller starch grains, indicating a delay in cellular differentiation. We conclude that a specific alteratio n in carbon metabolism can have pleiotropic effects on water and nitrogen c ontent and induces temporal changes in seed development.