I. Molecular response of higher plants exposed to low non-freezing temperature.
Plants can not escape from environmental changes like drought, pathogen attack, wounding or extreme temperature. They respond to these abiotic stresses by modulating the expression of a distinct set of genes. Of these, our group has been interested in genes involved in the cellular signalling underlying the reactions induced by low non-freezing temperature. Towards such a goal, we have isolated and characterized cDNA clones, of which the corresponding mRNAs are accumulated upon exposure to low temperature（Aguan et al. 1993; Kusano et al. 1995; Berberich et al. 1995; Berberich and Kusano 1997; Berberich et al. 1998; Kusano et al. 1998; Ito et al. 1999; Berberich et al. 1999; Yang et al. in press）.
Currently we have focused on the function of lip19 subfamily members which belong to the bZIP-gene family. These bZIP proteins localize to nuclei and preferentially bind to the sequence encompassing an A-box/G-box hybrid motif or a C-box/G-box hybrid motif. At least maize mLIP15 and two tobacco proteins, TBZ17 and TBZF, of the subfamily have a potential to transactivate downstream target genes (Yang et al. in press). Identification of TBZ17- and TBZF-target genes is under way. Expressional control of tbzF gene by low temperature is also addressed.
II. Molecular bases of senescense in higher plants (In preparation)
III. Towards to establish bio-system to recover heavy metal from polluted sites
We aim to establish a biotic system to recover heavy metals from contaminated eco-systems. To address to this goal, we started to characterize the mercuric ion transporter, MerC, isolated from Acidothiobacillus ferrooxidans E-15. Yeast cells (Saccharomyces cerevisiae) expressing merC in a galactose-inducible manner show hypersensitivity to cadmium, copper, cobalt and zinc ions compared to cells without merC. expression. Escherichia coli cells expressing merC show almost similar sensitivity as observed in the yeast cells to heavy metals except mercuric ions. These results indicate that MerC is not strict in metal recognition. Site-directed mutagenesis experiments are under way.
Recent Publications
- Yang, S. H., Yamaguchi, Y., Koizumi, N., Kusano, T. and H. Sano (2002)
- Promoter analysis of tbzF, a gene encoding a bZIP-type transcription factor, reveals distinct variation in cis-regions responsible for transcriptional activation between senescing leaves and flower buds in tobacco plants.
Plant Science 162: 973-980
- Yang, S. H., Berberich, T., Sano, H. and T. Kusano (2001)
- Specific association of transcripts of tbzF and tbz17, tobacco genes encoding bZIP-type transcriptional activators, with guard cells of senescing leaves and/or flowers.
Plant Physiol. 127(1): 23-32
- Berberich, T., Sano, H. and T. Kusano (1999)
- Involvement of a MAP kinase, ZmMPK5, in senescence and recovery from low-temperature-stress in maize.
Mol Gen Genet 262(3): 534-542
- Ito, K., Kusano, T. and K. Tsutsumi (1999)
- Cold-inducible bZIP protein gene in radish root regulated by calcium- and cycloheximide-mediated signals.
Plant Science, 142: 57-66
- Kusano, T., Sugawara, K., Harada, M. and T. Berberich (1998)
- Molecular cloning and partial characterization of a tobacco cDNA encoding a small bZIP protein.
Biochim. Biophys. Acta, 1395: 171-175
- Berberich, T., Sugawara, K., Harada, M., Kodama, H., Iba, K., and T. Kusano (1998)
- Two maize genes encoding plastidic _-3 fatty acid desaturase and their differential expression to temperature.
Plant Mol. Biol., 36: 297-306
- Berberich, T. and T. Kusano (1997)
- Cycloheximide induces a subset of low temperature inducible genes in maize.
Mol. Gen. Genet., 254: 275-283
- Inoue, C., Kusano, T. and Silver, S. (1996)
- Mercuric ion uptake by Escherichia coli cells producing Thiobacillus ferrooxidans MerC.
Biosci. Biotech. Biochem. 60: 1289-1292.
- Kusano, T., Berberich, T., Harada, M., Suzuki, N. and K. Sugawara (1995)
- A maize DNA binding factor with bZIP motif is induced by low temperature.
Mol. Gen. Genet. 248: 507-517
- Berberich, T., Sugawara, K., Harada, M. and T. Kusano (1995)
- Molecular cloning, characterization and expression of an elongation factor 1_ gene in maize.
Plant Mol. Biol., 29: 611-615
- Rawlings, DE and Kusano, T. (1994)
- Molecular genetics of Thiobacillus ferrooxidans.
Microbiological Rev. 58: 39-55.
- Aguan, K., Sugawara, K., Suzuki, N. and T. Kusano (1993)
- Low-temperature-dependent expression of a rice gene encoding a protein with a leucine-zipper motif.
Mol. Gen. Genet. 240:1-8
- Inoue, C., Sugawara, K. and Kusano, T. (1991)
- The merR regulatory gene in Thiobacillus ferrooxidans is spaced apart from the mer structural genes.
Mol. Microbiology 5: 2707-2718.
- Inoue, C., Sugawara, K. and Kusano, T. (1990)
- Thiobacillus ferrooxidans mer operon: sequence analysis of the promoter and adjacent genes.
Gene 96: 115-120.
- Kusano, T., Ji, G.-Y., Inoue, C. and Silver, S. (1990)
- Constitutive synthesis of a transport function encoded by the Thiobacillus ferrooxidans merC gene cloned in Escherichia coli.
J. Bacteriol. 172: 2688-2692.
- Inoue, C., Sugawara, K., Shiratori, T., Kusano, T. and Kitagawa, Y. (1989)
- Nucleotide sequence of the Thiobacillus ferrooxidans chromosomal gene encoding mercuric reductase.
Gene 84: 47-54.
- Shiratori, T., Inoue, C., Sugawara, K., Kusano, T. and Kitagawa, Y. (1989)
- Cloning and expression of Thiobaccilus ferrooxidans mercury ion resistance genes in Escherichia coli.
J, Bacterial. 171: 3458-3464.