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GENETICS, GENOMICS, AND MOLECULAR EVOLUTION

Barley Grain Maturation and Germination: Metabolic Pathway and Regulatory Network Commonalities and Differences Highlighted by New MapMan/PageMan Profiling Tools^1,[W],[OA]

Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung (IPK), D–06466 Gatersleben, Germany (N.S., V.R., U.S., N.S., W.W., M. Strickert, A.G., U.W.); Max-Planck-Institut für Molekulare Pflanzenphysiologie, D–14476 Potsdam-Golm, Germany (B.U., M. Stitt); and Department of Botany and Plant Sciences, University of California, Riverside, California 92521 (T.J.C.)

Plant seeds prepare for germination already during seed maturation. We performed a detailed transcriptome analysis of barley (Hordeum vulgare) grain maturation, desiccation, and germination in two tissue fractions (starchy endosperm/aleurone and embryo/scutellum) using the Affymetrix Barley1 GeneChip. To aid data evaluation, Arabidopsis thaliana MapMan and PageMan tools were adapted to barley. The analyses allow a number of conclusions: (1) Cluster analysis revealed a smooth transition in transcription programs between late seed maturation and germination within embryo tissues, but not in the endosperm/aleurone. (2) More than 12,000 transcripts are stored in the embryo of dry barley grains, many of which are presumably activated during germination. (3) Transcriptional activation of storage reserve mobilization events occurs at an early stage of germination, well before radicle protrusion. (4) Key genes of gibberellin (GA) biosynthesis are already active during grain maturation at a time when abscisic acid peaks suggesting the formation of an endogenous store of GA in the aleurone. This GA probably acts later during germination in addition to newly synthesized GA. (5) Beside the well-known role of GA in gene activation during germination spatiotemporal expression data and cis-element searches in homologous rice promoters confirm an equally important gene-activating role of abscisic acid during this developmental period. The respective regulatory webs are linked to auxin and ethylene controlled networks. In summary, new bioinformatics PageMan and MapMan tools developed in barley have been successfully used to investigate in detail the transcriptome relationships between seed maturation and germination in an important crop plant.

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: Nese Sreenivasulu (srinivas{at}ipk-gatersleben.de).

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

^[OA] Open Access articles can be viewed online without a subscription.

www.plantphysiol.org/cgi/doi/10.1104/pp.107.111781

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

Received October 26, 2007; accepted February 7, 2008; published February 15, 2008.