FRUCTAN ACCUMULATION AND SUCROSE METABOLISM IN TRANSGENIC MAIZE ENDOSPERM EXPRESSING A BACILLUS-AMYLOLIQUEFACIENS SACB GENE

Citation
Pg. Caimi et al., FRUCTAN ACCUMULATION AND SUCROSE METABOLISM IN TRANSGENIC MAIZE ENDOSPERM EXPRESSING A BACILLUS-AMYLOLIQUEFACIENS SACB GENE, Plant physiology, 110(2), 1996, pp. 355-363
Citations number
42
Categorie Soggetti
Plant Sciences
Journal title
ISSN journal
00320889
Volume
110
Issue
2
Year of publication
1996
Pages
355 - 363
Database
ISI
SICI code
0032-0889(1996)110:2<355:FAASMI>2.0.ZU;2-4
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 b een proposed. However, plants that accumulate these polymers are not a gronomically suited for large-scale cultivation or processing. This st udy describes the transformation of a Bacillus amyloliquefaciens SacB gene into maize (Zea mays L.) callus by particle bombardment. Tissue-s pecific expression and targeting of the SacB protein to endosperm vacu oles resulted in stable accumulation of high-molecular-weight fructan in mature seeds. Accumulation of fructan in the vacuole had no detecta ble effect on kernel development or germination. Fructan levels were f ound to be approximately 9-fold higher in sh(2) mutants compared to wi ld-type maize kernels. In contrast to vacuole-targeted expression, sta rch synthesis and endosperm development in mature seeds containing a c ytosolically expressed SacB gene were severely affected. The data demo nstrate that hexose resulting from cytosolic SacB activity was not uti lized for starch synthesis. Transgenic seeds containing a chimeric Sac B gene provide further evidence that the dominant pathway for starch s ynthesis in maize endosperm is through uridine diphosphoglucose cataly zed by the enzyme sucrose synthase.