Abstract
14C-Sugar uptake and incorporation into starch by slices of developing maize (Zea mays L.) endosperm were examined and compared with sugar uptake by maize endosperm-derived suspension cultures. Rates of sucrose, fructose, and d- and l-glucose uptake by slices were similar, whereas uptake rates for these sugars differed greatly in suspension cultures. Concentration dependence of sucrose, fructose, and d-glucose uptake was biphasic (consisting of linear plus saturable components) with suspension cultures but linear with slices. These and other differences suggest that endosperm slices are freely permeable to sugars. After diffusion into the slices, sugars were metabolized and incorporated into starch. Starch synthesis, but not sugar accumulation, was greatly reduced by 2.5 millimolar p-chloromercuribenzenesulfonic acid and 0.1 millimolar carbonyl cyanide m-chlorophenylhydrazone. Starch synthesis was dependent on kernel age and incubation temperature, but not on external pH (5 through 8). Competing sugars generally did not affect the distribution of 14C among the soluble sugars extracted from endosperm slices incubated in 14C-sugars. Competing hexoses reduced the incorporation of 14C into starch, but competing sucrose did not, suggesting that sucrose is not a necessary intermediate in starch biosynthesis. The bidirectional permeability of endosperm slices to sugars makes the characterization of sugar transport into endosperm slices impossible, however the model system is useful for experiments dealing with starch biosynthesis which occurs in the metabolically active tissue.
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Selected References
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- Echeverria E., Boyer C. D., Thomas P. A., Liu K. C., Shannon J. C. Enzyme activities associated with maize kernel amyloplasts. Plant Physiol. 1988 Mar;86(3):786–792. doi: 10.1104/pp.86.3.786. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Felker F. C., Goodwin J. C. Sugar uptake by maize endosperm suspension cultures. Plant Physiol. 1988 Dec;88(4):1235–1239. doi: 10.1104/pp.88.4.1235. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griffith S. M., Jones R. J., Brenner M. L. In Vitro Sugar Transport in Zea mays L. Kernels : I. Characteristics of Sugar Absorption and Metabolism by Developing Maize Endosperm. Plant Physiol. 1987 Jun;84(2):467–471. doi: 10.1104/pp.84.2.467. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Ponstein A. S., Vos-Scheperkeuter G. H., Jacobsen E., Feenstra W. J., Witholt B. Selective measurement of starch synthesizing enzymes in permeabilized potato tuber slices. Plant Physiol. 1990 Jan;92(1):234–241. doi: 10.1104/pp.92.1.234. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Porter G. A., Knievel D. P., Shannon J. C. Assimilate Unloading from Maize (Zea mays L.) Pedicel Tissues : II. Effects of Chemical Agents on Sugar, Amino Acid, and C-Assimilate Unloading. Plant Physiol. 1987 Oct;85(2):558–565. doi: 10.1104/pp.85.2.558. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Saftner R. A., Daie J., Wyse R. E. Sucrose uptake and compartmentation in sugar beet taproot tissue. Plant Physiol. 1983 May;72(1):1–6. doi: 10.1104/pp.72.1.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Setter T. L., Meller V. H. Reserve carbohydrate in maize stem : [C]glucose and [C]sucrose uptake characteristics. Plant Physiol. 1984 Jul;75(3):617–622. doi: 10.1104/pp.75.3.617. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shannon J. C. Carbon-14 Distribution in Carbohydrates of Immature Zea mays. Kernels Following CO(2) Treatment of Intact Plants. Plant Physiol. 1968 Aug;43(8):1215–1220. doi: 10.1104/pp.43.8.1215. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Shannon J. C. Movement of C-Labeled Assimilates into Kernels of Zea mays L: I. Pattern and Rate of Sugar Movement. Plant Physiol. 1972 Feb;49(2):198–202. doi: 10.1104/pp.49.2.198. [DOI] [PMC free article] [PubMed] [Google Scholar]