ALCOHOL-SOLUBLE PROTEINS AND PROTEIN BODY FORMATION IN THE ENDOSPERM OF TALL FESCUE

Alcohol-soluble proteins (prolamins) are the predominant storage prote ins in the endosperm of most of the cereals. Prolamins are deposited w ithin membrane bound structures called protein bodies. Our objective w as to determine if there is some commonality in protein body formation between agronomically important cereals and grasses. Sodium dodecyl s ulfate polyacrylamide gel electrophoresis (SDS-PAGE) of alcohol-solubl e proteins from tall fescue seeds revealed abundant proteins ranging i n size from 73 to 23 kDa. Immunoblot analysis using wheat (Triticum ae stivum L.) prolamin antiserum revealed limited antigenic homology betw een wheat and tall fescue (Festuca arundinaceae Schreb.) prolamins. Th e amino acid composition of tall fescue alcohol-soluble proteins showe d a high concentration of glutamine and proline residues, similar to t hose found in several cereal prolamins. Ultrastructural studies of the endosperm cells of tall fescue seeds at 15 d after anthesis revealed the presence of numerous vacuoles that contained protein inclusions. E xtensive rough endoplasmic reticulum was seen during this developmenta l stage. The endoplasmic reticulum, which was often dilated, gave rise to numerous, small vacuole-like structures. At 20 d after anthesis, t he rough endoplasmic reticulum contained flocculent material within th e lumen of the dilated areas. Protein aggregates were surrounded by nu merous vesicles whose membranes were studded with ribosomes. Organized membrane lattices were seen at the surface of protein bodies and at t he junctions where small protein bodies were fusing with larger ones. Protein A-gold immunocytochemistry employing wheat prolamin antiserum specifically localized the alcohol-soluble proteins within the protein bodies.