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Planta. 2003 Aug;217(4):628-38. Epub 2003 Apr 5.

Lysine-containing proteins in maize endosperm: a major contribution from cytoskeleton-associated carbohydrate-metabolizing enzymes.

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Laboratory of Molecular Cell Biology, Faculty of Agriculture, Ehime University, 790-8566 Matsuyama, Japan.


We measured fresh weight, dry weight, total protein, and the amounts of several individual proteins during endosperm development in three varieties of maize ( Zea mays L.): W64A wild-type (WT) and opaque-2 (o2), and sweet corn (SW). By 28 days after pollination (DAP), fresh weight was much higher in WT and SW than in o2, but o2 had a higher dry weight and thus a much lower water content. By 28 DAP, protein concentration [mg (g tissue(-1))] was highest in o2 and lowest in WT, while the protein content (microg seed(-1)) was lowest in o2. The storage proteins, alpha- and gamma-zeins, were low initially, but by 28 DAP they comprised over 50% of the total protein in WT and SW, but only about 30% in o2. In all varieties, the cytoskeleton proteins, actin, tubulin and eEF1alpha, sedimented with the protein bodies at 30 g to 27,000 g in tissue homogenized in cytoskeleton-stabilizing buffer. Other cytoskeleton-associated proteins increased during development, including UDP-glucose starch glucosyltransferase (UDP-GSGT, EC, sucrose synthase 1 (SuSy-1, EC and fructose-1,6 bisphosphate aldolase (FBA, EC At 28 DAP, these cytoskeleton-associated proteins combined make up 27% (WT), 23% (SW) and 33% (o2) of the total protein. These proteins are all rather high (5-11%) in lysine, and so they contribute about 75% (WT), 67% (o2), and 51% (SW) of the total endosperm lysine. We conclude that efforts to elevate the levels of these proteins could make a significant contribution to the nutritional value of corn.

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