Poster: Cytoskeleton: Structure & Function

Abs # 1116: Identification of the major lysine-containing proteins in maize endosperm.

Presenter:	Davies, Eric , eric_davies@ncsu.edu
Authors	Davies, Eric  (A)   Azama, Kishu  (B)   Abe, Shunnosuke  (B)   Sugimoto, Hideki  (B)
Affiliations:	(A): NC State University (B): Ehime University, JAPAN

We measured fresh weight, dry weight, total protein, and the amounts of several individual proteins during endosperm development in 3 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) was highest in o2 and lowest in WT, while the protein content (ug/seed) was lowest in o2. The storage proteins, alpha- and beta-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 eEF1a, 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 2.4.1.11), sucrose synthase 1 (SuSy-1, EC 2.4.1.13) and fructose-1,6 bisphosphate aldolase (FBA, EC 4.1.2.13). 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.