Biomedical subjects

Toshihiko Komari

Publications and source records attributed to Toshihiko Komari.

3 recordsLinked to original sources

PubMed2006

Binary vectors and super-binary vectors.

A binary vector is a standard tool in the transformation of higher plants mediated by Agrobacterium tumefaciens. It is composed of the borders of T-DNA, multiple cloning sites, replication functions for Escherichia coli and A. tumefaciens, selectable marker genes, reporter genes, and other accessory elements that can improve the efficiency of and/or give further capability to the system. A super-binary vector carries additional virulence genes from a Ti plasmid, and exhibits very high frequency of transformation, which is valuable for recalcitrant plants such as cereals. A number of useful vectors are widely circulated. Whereas vectors with compatible selectable markers and convenient cloning sites are usually the top criteria when inserting gene fragments shorter than 15 kb, the capability of maintaining a large DNA piece is more important for consideration when introducing DNA fragments larger than 15 kb. Because no vector is perfect for every project, it is recommended that modification or construction of vectors should be made according to the objective of the experiments. Existing vectors serve as good sources of components.

Agrobacterium tumefaciens↗

PubMed2005

Differential expression pattern of C4 bundle sheath expression genes in rice, a C3 plant.

NADP-malic enzyme (NADP-ME) and phosphoenolpyruvate carboxykinase (PCK) are specifically expressed in bundle sheath cells (BSCs) in NADP-ME-type and PCK-type C4 plants, respectively. Unlike the high activities of these enzymes in the green leaves of C4 plants, their low activities have been detected in the leaves of C3 plants. In order to elucidate the differences in the gene expression system between C3 and C4 plants, we have produced chimeric constructs with the beta-glucuronidase (GUS) reporter gene under the control of the maize NADP-Me (ZmMe) or Zoysia japonica Pck (ZjPck) promoter and introduced these constructs into rice. In leaves of transgenic rice, the ZmMe promoter directed GUS expression not only in mesophyll cells (MCs) but also in BSCs and vascular cells, whereas the ZjPck promoter directed GUS expression only in BSCs and vascular cells. Neither the ZjPck nor ZmMe promoters induced GUS expression due to light. In rice leaves, the endogenous NADP-Me (OsMe1) was expressed in MCs, BSCs and vascular cells, whereas the rice Pck (OsPck1) was expressed only in BSCs and vascular cells. Taken together, the results obtained from transgenic rice demonstrate that the expression pattern of ZmMe or ZjPck in transgenic rice was reflected by that of its counterpart gene in rice.

Chimera↗

PubMed2002

Accumulation of maize response regulator proteins in mesophyll cells after cytokinin treatment.

The maize response regulator genes ZmRR1 and ZmRR2 respond to cytokinin, and the translated products seem to be involved in nitrogen signal transduction mediated by cytokinin through the His-Asp phosphorelay. To elucidate the physiological function of the proteins, we examined the temporal and spatial distribution in maize leaves by immunochemical analysis and use of transgenic plants. ZmRR1 and ZmRR2 polypeptides could be distinctively detected by western blotting. The polypeptides accumulated in leaves within 5 h of the supply of nitrate to nitrogen-depleted maize, and the accumulation was transient. The extent of induction was larger in the leaf tip, which is rich in photosynthetically matured cells, than elsewhere. In leaves, the polypeptides accumulated mostly in mesophyll cells. Histochemical analyses of transgenic maize harboring a ZmRR1 promoter-beta-glucuronidase fusion gene also showed most of the expression to be in these cells. These results suggest that ZmRR1 and ZmRR2 are induced in mesophyll cells and function in nitrogen signal transduction mediated by cytokinin.

Cytokinins↗