Different hormonal regulation of cellular differentiation and function in nucellar projection and endosperm transfer cells: A microdissection-based transcriptome study of young barley grains

Johannes Thiel, Diana Weier, Nese Sreenivasulu, Marc Strickert, Nicola Weichert, Michael Melzer, Tobias Czauderna, Ulrich Wobus, Hans Weber, Winfriede Weschke

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Nucellar projection (NP) and endosperm transfer cells (ETC) are essential tissues in growing barley (Hordeum vulgare) grains, responsible for nutrient transfer from maternal to filial tissues, endosperm/embryo nutrition, and grain development. A laser microdissection pressure catapulting-based transcriptome analysis was established to study NP and ETC separately using a barley 12K macroarray. A major challenge was to isolate high-quality mRNA from preembedded, fixed tissue while maintaining tissue integrity. We show that probes generated from fixed and embedded tissue sections represent largely the transcriptome (>70%) of nonchemically treated and nonamplified references. In NP, the top-down gradient of cellular differentiation is reflected by the expression of C3HC4-type ubiquitin ligases and different histone genes, cell wall biosynthesis and expansin/extensin genes, as well as genes involved in programmed cell death-related proteolysis coupled to nitrogen remobilization, indicating distinct areas simultaneously undergoing mitosis, cell elongation, and disintegration. Activated gene expression related to gibberellin synthesis and function suggests a regulatory role for gibberellins in establishment of the differentiation gradient. Upregulation of plasmalemma-intrinsic protein and tonoplast-intrinsic protein genes indicates involvement in nutrient transfer and/or unloading. In ETC, AP2/EREBP-like transcription factors and ethylene functions are transcriptionally activated, a response possibly coupled to activated defense mechanisms. Transcriptional activation of nucleotide sugar metabolism may be attributed to ascorbate synthesis and/or cell wall biosynthesis. These processes are potentially controlled by trehalose-6-P synthase/phosphatase, as suggested by expression of their respective genes. Up-regulation of amino acid permeases in ETC indicates important roles in active nutrient uptake from the apoplastic space into the endosperm.

Original languageEnglish
Pages (from-to)1436-1452
Number of pages17
JournalPlant Physiology
Issue number3
Publication statusPublished - 1 Nov 2008
Externally publishedYes

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