|Hurkman Ii, William|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2006
Publication Date: 4/4/2006
Citation: Balmer, Y., Vensel, W.H., Dupont, F.M., Buchanan, B., Hurkman, W.J. 2006. Proteome of amyloplasts isolated developing wheat endosperm presents evidence of broad metabolic capability. Journal of Experimental Botany. 57(7): 1591-1602 Interpretive Summary: Amyloplasts are organelles that synthesize and store starch in plants. Starch is a major component of the wheat grain endosperm where it serves as a carbohydrate reserve that supports germination and early seedling growth. Aside from pathways leading to the synthesis and breakdown of starch, relatively little is known about the biochemistry of amyloplasts. To help fill this gap, we surveyed the amyloplast proteome using 2-D gel electrophoresis and mass spectrometry. Our study led to the identification of 295 proteins that function in a range of processes. The amyloplast not only functions in carbohydrate metabolism, but also in cytoskeleton/plastid division, energetics, nitrogen and sulfur metabolism, nucleic acid-related reactions, synthesis of various building blocks, protein-related reactions, transport, signaling, and stress/defense responses. The results add to our understanding of amyloplast function and demonstrate the broad biosynthetic capabilities of this organelle. Knowledge of cellular processes in the amyloplast is essential for understanding complex crop traits such as productivity and quality.
Technical Abstract: In contrast to chloroplasts, our knowledge of amyloplasts—the organelles that synthesize and store starch in heterotrophic plant tissues—is in a formative stage. While our understanding of what is considered their primary function, i.e., the biosynthesis and degradation of starch, has increased dramatically in recent years, we know relatively little about other biochemical processes taking place in these organelles. To help fill this gap, we have conducted a proteomic analysis of amyloplasts isolated from the starchy endosperm of wheat seeds (10 days post anthesis). Our study has led to the identification of 295 proteins that function in a range of processes, including carbohydrate metabolism, cytoskeleton/plastid division, energetics, nitrogen and sulfur metabolism, nucleic acid-related reactions, synthesis of various building blocks, protein-related reactions, transport, signaling, stress and a variety of other activities grouped under “Miscellaneous.” The function of 7% of the proteins was unknown. The results highlight the role of the amyloplast as a starch-storing organelle that fulfills a spectrum of biosynthetic needs of the parent tissue. When compared with a recent proteomic analysis of whole endosperm (Vensel et al., 2005), the current study demonstrates the advantage of using isolated organelles in proteomic studies.