| Seeing is believing: Microdissection of plant tissue (03-04-2008) |
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Cell-specific resolution of gene expression analysis is critical when developmental processes or responses to the environment are assessed. Together with Simonetta Santi from the University of Udine, Wolfgang Schmidt’s team analyzed the functional fate of rhizodermal cells that have been re-programmed by iron deficiency using the Laser Microdissection Pressure Catapulting technique (Journal of Experimental Botany, Advanced Access). For the first time, quantitative data on environmentally-triggered transcript changes in a single cell type were provided, which allows insights in the roles of particular genes in a given adaptive process. |
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Multiple shoot proliferation from slipper orchid seed callus (03-05-2008)
Commercial Paphiopedilum propagation by growers has still been entirely through asymbiotic germination. Wei-chin Chang’s team first invented a protocol for obtaining plantlets from protocorm-derived callus (Plant Cell Tiss. & Org. Cult. 62: 21-25. 2000). Recently, they have further improved the method by shortening the duration of callus induction from seeds, increasing the number of regenerated shoots and increasing mass proliferation of regenerants from regenerated shoots (PI Hong, JT Chen, WC Chang, Plant regeneration via protocorm-like body formation and shoot multiplication from seed-derived callus of a maudiae type slipper orchid. Acta Physiologiae Plantarum 2008, in press). |
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Novel histone demethylases found in baker’s yeast (01-23-2008) |
  
Chromatin is composed of histone octamers (histones H2A, H2B, H3 and H4), which associate with DNA into nucleosomes. The covalent modification of histones in the chromatin structure plays a pivotal role in epigenetic control of gene expression, cell growth and development. Histone modification by methylation was once considered extremely stable and irreversible. This view has recently changed with the identification of two mammalian demethylase families, LSD1 (Lysine specific demethylase1) and a Jumonji C (JmjC) domain containing protein family, that catalyse the oxidative demethylation of lysine residues in histones. In collaboration with Dr. Ming-Daw Tsai in the Genomics Research Center, IPMB’s Dr. Wan-Sheng Sunny Lo examined the function of four JmjC domain containing proteins in S. crevisiae by high-resolution mass spectrometry (MS) analyses of histone H3 methylation. Their results demonstrate that the yeast JmjC proteins also have demethylation activity at histone H3 K36 and K4. Together, the results identify new demethylases in yeast and their sites of action (J. Biol. Chem. 282:14262-71,2007).
In general, histone demethylases are involved in important biological processes such as transcriptional regulation, DNA repair and heterochromatin formation by antagonizing the repressive effect of histone Lys-methylation. The methodology described in this work will be useful in identifying histone demethylases and their target sites in other organisms, including plants . For example, it has been demonstrated that chromatin modifications play an important role in the regulation of flowering time in Arabidopsis thaliana. The possible role of histone demethylation by Jmjc proteins in flowering time control and other developmental regulation is under investigation. |
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