This Article Full Text Full Text (PDF) Supplemental Data All Versions of this Article: 150/1/190    most recent pp.108.133520v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Radchuk, V. V. Articles by Weschke, W. Search for Related Content PubMed PubMed Citation Articles by Radchuk, V. V. Articles by Weschke, W. Agricola Articles by Radchuk, V. V. Articles by Weschke, W.

DEVELOPMENT AND HORMONE ACTION

Spatiotemporal Profiling of Starch Biosynthesis and Degradation in the Developing Barley Grain^1,[W]

Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D–06466 Gatersleben, Germany

Barley (Hordeum vulgare) grains synthesize starch as the main storage compound. However, some starch is degraded already during caryopsis development. We studied temporal and spatial expression patterns of genes coding for enzymes of starch synthesis and degradation. These profiles coupled with measurements of selected enzyme activities and metabolites have allowed us to propose a role for starch degradation in maternal and filial tissues of developing grains. Early maternal pericarp functions as a major short-term starch storage tissue, possibly ensuring sink strength of the young caryopsis. Gene expression patterns and enzyme activities suggest two different pathways for starch degradation in maternal tissues. One pathway possibly occurs via -amylases 1 and 4 and β-amylase 1 in pericarp, nucellus, and nucellar projection, tissues that undergo programmed cell death. Another pathway is deducted for living pericarp and chlorenchyma cells, where transient starch breakdown correlates with expression of chloroplast-localized β-amylases 5, 6, and 7, glucan, water dikinase 1, phosphoglucan, water dikinase, isoamylase 3, and disproportionating enzyme. The suite of genes involved in starch synthesis in filial starchy endosperm is much more complex than in pericarp and involves several endosperm-specific genes. Transient starch turnover occurs in transfer cells, ensuring the maintenance of sink strength in filial tissues and the reallocation of sugars into more proximal regions of the starchy endosperm. Starch is temporally accumulated also in aleurone cells, where it is degraded during the seed filling period, to be replaced by storage proteins and lipids.

² These authors contributed equally to the article.

The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Volodymyr V. Radchuk (radchukv{at}ipk-gatersleben.de).

^[W] The online version of this article contains Web-only data.

www.plantphysiol.org/cgi/doi/10.1104/pp.108.133520

^* Corresponding author; e-mail radchukv{at}ipk-gatersleben.de.

Received December 1, 2008; accepted March 19, 2009; published March 25, 2009.