de Sousa, S.M. , Hunter, C.T.III , Ankumah, N. , Avigne, W.T. , Koch, K.E. .
A sorbitol dehydrogenase deficiency reduces kernel size in maize.
Sucrose arriving at the kernel can be cleaved by either invertase or the reversible sucrose synthase reaction. In either case, fructose is a product. Fructose is typically phosphorylated by hexokinase, and then used for respiration or polysaccharide biosynthesis. Alternatively, fructose may follow a less well-known fate in some tissues, where it can be converted to sorbitol by sorbitol dehydrogenase (SDH). This enzyme is highly active in maize endosperm, but since kernels do not store sorbitol, an intermediary role is likely. To help test hypotheses for the significance of sorbitol dehydrogenase in maize, we screened the UniformMu maize population and identified an sdh1 mutant (the sole gene for SDH in maize or rice genomes). Since the UniformMu population is highly inbred, the wild type material provides a uniform set of controls for functional analysis of the mutants. The sdh1 mutation reduced maximal SDH activity in developing kernel to less than 6% of that in wild type by quantified assays. Quantification of the small-kernel phenotype showed a 21% reduction in dried-seed weight in first-round field analyses (significant to p<.001). The role of sorbitol in developing maize kernels is potentially pivotal, but remains undefined. Sorbitol may function as an intermediate metabolite and/or shuttle aiding transfer of carbon resources and reducing power (NAD[P]H) within the endosperm and/or to the embryo. Elucidation of the sorbitol pathway will allow an appraisal of its importance to the metabolic and physical flux of carbon through the endosperm and to the embryo in the developing maize kernel.
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1 - University of Florida, Department of Horticultural Sciences, Fifield Hall POBox 110690, Gainesville, Florida, 32611, USA
2 - University of Florida, Department of Horticultural Sciences
Presentation Type: ASPB Minisymposium
Location: Continental C/Hilton
Date: Sunday, July 8th, 2007
Time: 4:10 PM