Biomedical subjects

Taku Demura

Publications and source records attributed to Taku Demura.

4 recordsLinked to original sources

PubMed2002

Visualization by comprehensive microarray analysis of gene expression programs during transdifferentiation of mesophyll cells into xylem cells.

Plants have a unique transdifferentiation mechanism by which differentiated cells can initiate a new program of differentiation. We used a comprehensive analysis of gene expression in an in vitro zinnia (Zinnia elegans L.) culture model system to gather fundamental information about the gene regulation underlying the transdifferentiation of plant cells. In this model, photosynthetic mesophyll cells isolated from zinnia leaves transdifferentiate into xylem cells in a morphogenic process characterized by features such as secondary-wall formation and programmed cell death. More than 8,000 zinnia cDNA clones were isolated from an equalized cDNA library prepared from cultured cells transdifferentiating into xylem cells. Microarray analysis using these cDNAs revealed several types of unique gene regulation patterns, including: the transient expression of a set of genes during cell isolation, presumably induced by wounding; a rapid reduction in the expression of photosynthetic genes and the rapid induction of protein synthesis-associated genes during the first stage; the preferential induction of auxin-related genes during the subsequent stage; and the transient induction of genes closely associated with particular morphogenetic events, including cell-wall formation and degradation and programmed cell death during the final stage. This analysis also revealed a number of previously uncharacterized genes encoding proteins that function in signal transduction, such as protein kinases and transcription factors that are expressed in a stage-specific manner. These findings provide new clues to the molecular mechanisms of both plant transdifferentiation and wood formation.

Asteraceae↗

PubMed2002

The advantages of cDNA microarray as an effective tool for identification of reproductive organ-specific genes in a model legume, Lotus japonicus.

To understand the molecular mechanisms intrinsic to reproductive organ development a cDNA microarray, fabricated from flower bud cDNA clones, was used to isolate genes, which are specifically expressed during the development of the anther and pistil in Lotus japonicus. Cluster analysis of the microarray data revealed 21 and 111 independent cDNA groups, which were specifically expressed in immature and mature anthers, respectively. RT-PCR was performed to provide a direct assessment of the accuracy and reproducibility of our approach. Confirmation of our results suggests that cDNA microarray technology is an effective tool for identification of novel reproductive organ-specific genes.

Cluster Analysis↗

PubMed2002

Analysis of early processes in wound-induced vascular regeneration using TED3 and ZeHB3 as molecular markers.

Interruption of the vascular bundles of Zinnia internodes induced transdifferentiation of cells into tracheary elements (TEs) or sieve elements (SEs) within 4 d of wounding. The early stage of the regeneration processes was analyzed using two molecular marker genes, TED3 and ZeHB3, which are expressed specifically in TE precursor cells and immature phloem cells, respectively. An increase in the numbers of TED3 and ZeHB3 mRNA-expressing cells always preceded an increase in the numbers of TEs and SEs formed. The earliest sign of vascular differentiation was the appearance 24 h after wounding of a layer(s) of TED3 mRNA-expressing cells in the inter- and intrafascicular cambial-like regions along the severed vascular bundles. In contrast, the number of ZeHB3 mRNA-expressing cells decreased dramatically along the severed bundles 24 h after wounding, and increased again 36 h after wounding. These results clearly indicate that xylem and phloem differentiation are not synchronized during vascular regeneration. Treatment with 10(-3) M colchicine abolished the expression of ZeHB3 mRNA in pith parenchyma, but not TED3 mRNA; this suggests that cell division is a prerequisite for the transdifferentiation of pith parenchymal cells into immature phloem cells expressing ZeHB3. In contrast, transdifferentiation of pith parenchymal cells to TE precursor cells does not require preceding cell division. However, the inhibition of cell division prevented the formation of both radial files of TEs and the cambial-like layer(s) of TED3 mRNA-expressing cells, and, ultimately, vascular regeneration altogether. These results imply that wound-induced cambial-like activity in and between severed vascular bundles is essential for vascular regeneration.

Asteraceae↗

PubMed2002

Promotion of transcript accumulation of novel Zinnia immature xylem-specific HD-Zip III homeobox genes by brassinosteroids.

We isolated three novel homeobox genes (ZeHB-10, -11 and -12) from Zinnia elegans to elucidate the molecular mechanism underlying vascular system formation. ZeHB-10, -11 and -12 encode for HD-Zip proteins of the class III to which Arabidopsis Athb-8, -9, -14, -15 and IFL1 belong. In situ hybridization analysis demonstrated that the ZeHB-10, -11 and -12 mRNAs accumulated preferentially in procambium and immature xylem cells in 14-day-old plants. Transcripts for the three genes also accumulated in cultured Zinnia cells in a xylogenesis-specific manner. The accumulation of transcripts for all of ZeHB-10, -11 and -12 in cultured Zinnia cells was suppressed strongly by uniconazole, an inhibitor of brassinosteroid synthesis, and such suppression was reversed by the addition of brassinolide, a biologically active brassinosteroid. Thus the expression of ZeHB-10, -11 and -12 may be regulated by endogenous levels of brassinosteroids. Taken together with the fact that ZeHB-10, -11 and -12 proteins can bind to each other in yeast, the roles of HD-Zip III genes in vascular development are discussed.

Arabidopsis Proteins↗