Dr. Toshiro Shigaki Visiting Scientist Plant Molecular Biology Indian Institute of Advanced Research Tel.: 91-79-30514213 Fax: +91-79-30514110 E-mail: tshigakiiiar.res.in

Mailing address: The Puri Foundation For Education in India, Block No 2: First Floor, Udyog Bhavan, Sector No 11, Gandhingar - 382017 Gujarat.

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Research interests:

My research focuses on (1) the improvement of the nutritional value of plants and (2) remediation of contaminated soils by plants (phytoremediation).  To achieve these goals, I engineer transporter proteins to enhance their substrate specificity and efficiency.  I chose a group of transporters called CAXs.  CAXs are mainly localized to the tonoplast, where they transfer cations (Ca2+ and other nutrient/toxic metals) into the vacuole along the proton gradient that exists between the vacuole (low pH) and cytoplasm.  Once in the vacuole, the metals are physiologically inactive.  Therefore, CAXs are ideal for nutrition enhancement and phytoremediation.

At IAR  new CAXs will be isolated from the native plants that have not been the traditional targets of CAX research.  This project should identify CAXs that are novel in substrate specificity and will prove to be useful for phytoremediation in India.

We are also working on the emerging area of the DNA barcoding of plants.  Our initial project aims to facilitate the identification of local acacia species, which has been ecologically and economically important in this area.

1. 2006.  T. Shigaki, I. Rees, L. Nakhleh, and K. D. Hirschi.  Identification of three distinct phylogenetic groups of CAX cation/proton antiporters.  Journal of Molecular Evolution 63:815-825.
2. 2006.  C. K. Kim, J. -S. Han, H. S. Lee, J. Y. Oh, T. Shigaki, S. H. Park, and K. D. Hirschi.  Expression of an Arabidopsis CAX2 variant in potato tubers increases calcium levels with no accumulation of manganese.  Plant Cell Reports 25:1226-1232.
3. 2006.  T. Shigaki and K. D. Hirschi.  Diverse functions and molecular properties emerging for CAX cation/H+ exchangers in plants.  Plant Biology 8:419-429.
4. 2005.  T. Shigaki, M. Kole, J. M. Ward, H. Sze, and K. D. Hirschi.  Cre-loxP recombination vectors for the expression of Riken Arabidopsis full-length cDNAs in plants.  BioTechniques 39:301-304.
5. 2005.  T. Shigaki, B. J. Barkla, M. C. M. Vergara, J. Zhao, O. Pantoja, and K. D. Hirschi.  Identification of a crucial histidine involved in metal transport activity in the Arabidopsis cation/proton exchanger CAX1.  Journal of Biological Chemistry 280:30136-30142.
6. 2005.  T. Shigaki, R. R. Vyzasatya, A. B. Sivitz, J. M. Ward, H. Sze, and K. D. Hirschi.  The Cre-loxP recombination-based reporter system for plant transcriptional expression studies.  Plant Molecular Biology 58:65-73.
7. 2003.  T. Shigaki, J. K. Pittman, and K. D. Hirschi.  Manganese specificity determinants in the Arabidopsis metal/H+ antiporter CAX2.  Journal of Biological Chemistry 278:6610-6617.
8. 2002.  T. Shigaki, C. Sreevidya, and K. Hirschi.  Analysis of the Ca2+ domain in the Arabidopsis H+/Ca2+ antiporters CAX1 and CAX3.  Plant Molecular Biology 50:475-483.
9. 2002.  J. K. Pittman, T. Shigaki, N. -H. Cheng, and K. D. Hirschi.  Mechanism of N-terminal autoinhibition in the Arabidopsis Ca2+/H+ antiporter CAX1.  Journal of Biological Chemistry 277:26452-26459.
10. 2002.  T. Shigaki and K. D. Hirschi.  Chimeric gene construction without reference to restriction sites.  BioTechniques 32:736-740.
11.  2001.  T. Shigaki, N. -H. Cheng, J. K. Pittman, and K. Hirschi. Structural determinants of Ca2+ transport in the Arabidopsis H+/Ca2+ antiporter CAX1.  Journal of Biological Chemistry 276:43152-43159.
12. 2001.  T. Shigaki and K. D. Hirschi.  Use of Class IIS restriction enzymes for site-directed mutagenesis: variations on phoenix mutagenesis.  Analytical Biochemistry 298:118-120.