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Schubert I.,Leibniz Institute of Plant Genetics and Crop Plant Research | Shaw P.,John Innes Center
Trends in Plant Science | Year: 2011

Eukaryotic chromosomes occupy distinct territories within interphase nuclei. The arrangement of chromosome territories (CTs) is important for replication, transcription, repair and recombination processes. Our knowledge about interphase chromatin arrangement is mainly based on results from in situ labeling approaches. The phylogenetic affiliation of a species, cell cycle, differentiation status and environmental factors are all likely to influence interphase nuclear architecture. In this review we survey current data about relative positioning of CTs, somatic pairing of homologs, and sister chromatid alignment in meristematic and differentiated tissues, using data derived mainly from Arabidopsis thaliana, wheat (Triticum aestivum) and their relatives. We discuss morphological constraints and epigenetic impacts on nuclear architecture, the evolutionary stability of CT arrangements, and alterations of nuclear architecture during transcription and repair. © 2011 Elsevier Ltd.

Longin C.F.H.,University of Hohenheim | Reif J.C.,Leibniz Institute of Plant Genetics and Crop Plant Research
Trends in Plant Science | Year: 2014

More than half a million wheat genetic resources are resting in gene banks worldwide. Unlocking their hidden favorable genetic diversity for breeding is pivotal for enhancing grain yield potential, and averting future food shortages. Here, we propose exploiting recent advances in hybrid wheat technology to uncover the masked breeding values of wheat genetic resources. The gathered phenotypic information will enable a targeted choice of accessions with high value for pre-breeding among this plethora of genetic resources. We intend to provoke a paradigm shift in pre-breeding strategies for grain yield, moving away from allele mining toward genome-wide selection to bridge the yield gap between genetic resources and elite breeding pools. © 2014 Elsevier Ltd.

Thiel J.,Leibniz Institute of Plant Genetics and Crop Plant Research
Frontiers in Plant Science | Year: 2014

Endosperm transfer cells (ETCs) are positioned at the intersection of maternal and filial tissues in seeds of cereals and represent a bottleneck for apoplasmic transport of assimilates into the endosperm. Endosperm cellularization starts at the maternal-filial boundary and generates the highly specialized ETCs. During differentiation barley ETCs develop characteristic flange-like wall ingrowths to facilitate effective nutrient transfer. A comprehensive morphological analysis depicted distinct developmental time points in establishment of transfer cell (TC) morphology and revealed intracellular changes possibly associated with cell wall metabolism. Embedded inside the grain, ETCs are barely accessible by manual preparation. To get tissue-specific information about ETC specification and differentiation, laser microdissection (LM)-based methods were used for transcript and metabolite profiling. Transcriptome analysis of ETCs at different developmental stages by microarrays indicated activated gene expression programs related to control of cell proliferation and cell shape, cell wall and carbohydrate metabolism reflecting the morphological changes during early ETC development. Transporter genes reveal distinct expression patterns suggesting a switch from active to passive modes of nutrient uptake with the onset of grain filling. Tissue-specific RNA-seq of the differentiating ETC region from the syncytial stage until functionality in nutrient transfer identified a high number of novel transcripts putatively involved in ETC differentiation. An essential role for two-component signaling (TCS) pathways in ETC development of barley emerged from this analysis. Correlative data provide evidence for abscisic acid and ethylene influences on ETC differentiation and hint at a crosstalk between hormone signal transduction and TCS phosphorelays. Collectively, the data expose a comprehensive view on ETC development, associated pathways and identified candidate genes for ETC specification. © 2014 Thiel.

Shi R.,Leibniz Institute of Plant Genetics and Crop Plant Research
The New phytologist | Year: 2012

• Retranslocation of iron (Fe) from source leaves to sinks requires soluble Fe binding forms. As much of the Fe is protein-bound and associated with the leaf nitrogen (N) status, we investigated the role of N in Fe mobilization and retranslocation under N deficiency- vs dark-induced leaf senescence. • By excluding Fe retranslocation from the apoplastic root pool, Fe concentrations in source and sink leaves from hydroponically grown barley (Hordeum vulgare) plants were determined in parallel with the concentrations of potential Fe chelators and the expression of genes involved in phytosiderophore biosynthesis. • N supply showed opposing effects on Fe pools in source leaves, inhibiting Fe export out of source leaves under N sufficiency but stimulating Fe export from source leaves under N deficiency, which partially alleviated Fe deficiency-induced chlorosis. Both triggers of leaf senescence, shading and N deficiency, enhanced NICOTIANAMINE SYNTHASE2 gene expression, soluble Fe pools in source leaves, and phytosiderophore and citrate rather than nicotianamine concentrations. • These results indicate that Fe mobilization within senescing leaves is independent of a concomitant N sink in young leaves and that phytosiderophores enhance Fe solubility in senescing source leaves, favoring subsequent Fe retranslocation. © 2012 The Authors. New Phytologist © 2012 New Phytologist Trust.

Schubert V.,Leibniz Institute of Plant Genetics and Crop Plant Research
Cytogenetic and Genome Research | Year: 2014

RNA polymerase II (RNAPII) is responsible for the transcription of most eukaryotic genes. In mammalian nuclei, RNAPII is mainly localized in relatively few distinct transcription factories. In this study-applying super-resolution microscopy-it is shown that in plants, inactive (non-phosphorylated) and active (phosphorylated) RNAPII modifications compose distinct 'transcription networks' within the euchromatin. These reticulate structures sometimes attach to each other, but they are absent from heterochromatin and nucleoli. The global RNAPII distribution within nuclei is not influenced by interphase chromatin organization such as Rabl (rye) versus non-Rabl (Arabidopsis thaliana) orientation. Replication of sister chromatids without cell division causes endopolyploidy, a phenomenon widespread in plants and animals. Endopolyploidy raises the number of gene copies per nucleus. Here, it is shown that the amounts of active and inactive RNAPII enzymes in differentiated 2-32C leaf nuclei of A. thaliana proportionally increase with rising endopolyploidy. Thus, increasing the transcriptional activity of cells and tissues seems to be an important function of endopolyploidy. © 2014 S. Karger AG, Basel.

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