title: Fructan Accumulation and Sucrose Metabolism in Transgenic Maize Endosperm Expressing a Bacillus amyloliquefaciens SacB Gene.
abstract: Over 40,000 species of plants accumulate fructan, [beta]-2-1- and [beta]-2-6-linked polymers of fructose as a storage reserve. Due to their high fructose content, several commercial applications for fructans have been proposed. However, plants that accumulate these polymers are not agronomically suited for large-scale cultivation or processing. This study describes the transformation of a Bacillus amyloliquefaciens SacB gene into maize (Zea mays L.) callus by particle bombardment. Tissue-specific expression and targeting of the SacB protein to endosperm vacuoles resulted in stable accumulation of high-molecular-weight fructan in mature seeds. Accumulation of fructan in the vacuole had no detectable effect on kernel development or germination. Fructan levels were found to be approximately 9-fold higher in sh2 mutants compared to wild-type maize kernels. In contrast to vacuole-targeted expression, starch synthesis and endosperm development in mature seeds containing a cytosolically expressed SacB gene were severely affected. The data demonstrate that hexose resulting from cytosolic SacB activity was not utilized for starch synthesis. Transgenic seeds containing a chimeric SacB gene provide further evidence that the dominant pathway for starch synthesis in maize endosperm is through uridine diphosphoglucose catalyzed by the enzyme sucrose synthase.
authors.affiliation: Agricultural Products, E. I. DuPont de Nemours & Co., Wilmington, Delaware 19880-0402.
authors.forename: P. G.
authors.initials: PG
authors.lastname: Caimi
authors.forename: L. M.
authors.initials: LM
authors.lastname: McCole
authors.forename: T. M.
authors.initials: TM
authors.lastname: Klein
authors.forename: P. S.
authors.initials: PS
authors.lastname: Kerr