Julian I. Schroeder
e-mail: julian@biomail.ucsd.edu
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The molecular mechanisms of signal transduction pathways in higher plant cells are essential to vital processes such as hormone and light perception, growth, development, stress resistance, and nutrient uptake from soils. Our research focuses on molecular and cell biological elucidation of signal transduction cascades in higher plant cells. The chain of events is being defined by which plant cells translate hormone reception and environmental signals to specific cell biological responses. In particular our research focuses on signal transduction mechanisms which control guard cell movements and metal transport in roots.
Stomatal pores in the epidermis of leaves allow CO2 exchange with the atmosphere and account for transpirational water loss of plants (see figure). Two guard cells surround each pore and control the opening and closing of stomata. In guard cells, cell biological, molecular, and time-resolved Ca2+ imaging studies on genetic signaling mutants in Arabidopsis are allowing us to identify and characterize novel signal transduction mechanisms and cascades. Furthermore, we are combining these analyses with new genomic, bioinformatic and proteomic approaches towards discovering new signaling mechanisms. We have recently identified new early signal transduction mechanisms mediated by the plant hormone abscisic acid and have obtained molecular genetic, cell biological, genomic, biophysical whole plant physiological evidence for new genes and mechanisms in guard cells that reduce water loss of Arabidopsis during drought.
A second effort in the lab focuses on identifying genes that
mediate nutrient and heavy metal uptake in roots. In roots we
have cloned important nutrient uptake transporters and are analyzing
their molecular physiological roles and structures with special
focus on plant nutrition, metal toxicity and environmental remediation
by removal of heavy metals from soils. We have identified important
genes that mediate metal transport and heavy metal detoxification
in plants. Transgenic plant analyses, Arabidopsis genetics,
bioinformatics, knock-out techniques, microarray analyses, heterologous
expression in yeast, Xenopus oocytes, and E. coli
and single cell analysis techniques including time-resolved confocal
imaging are being applied in both of the above projects. Members
in the lab are being trained in the above interdisciplinary techniques
while pursuing individual research projects.
Mori, I.C., Murata, Y., Yang, Y., Munemasa, S., Wang, Y.F., Andreoli, S., Tiriac, H., Alonso, J.M., Harper, J.F., Ecker, J.R., Kwak, J.M., Schroeder, J.I. (2006). CDPKs CPK6 and CPK3 Function in ABA Regulation of Guard Cell S-Type Anion- and Ca(2+)- Permeable Channels and Stomatal Closure. PloS Biol. 4.
Schroeder, J.I., Nambara, E. (2006). A quick release mechanism for abscisic acid. Cell 126: 1023-1025.
Young, J.J., Mehta, S., Israelsson, M., Godoski, J., Grill, E., Schroeder, J.I. (2006). CO2 signaling in guard cells: Calcium sensitivity response modulation, a Ca2+ - independent phase, and CO2 insensitivity of the gca2 mutant. Proc. Natl. Acad. Sci. USA 103: 7506-7511.
Schroeder, J.I. (2006). Physiology: nitrate at the ion exchange. Nature 442: 877-878.
Hashimoto, M., Negi, J., Young, J., Israelsson, M., Schroeder, J.I., Iba, K. (2006). Arabidopsis HT1 kinase controls stomatal movements in response to CO2. Nature Cell Biol. 8: 391-397.
Colcombet, J., Boisson-Dernier, A., Ros-Palau, R., Vera, C.E., Schroeder, J.I. (2005). Arabidopsis somatic embryogenesis receptor kinases 1 and 2 are essential for tapetum development and microspore maturation. Plant Cell 17: 3350-3361.
Leonhardt, N., Kwak, J. M., Robert, N., Waner, D., Leonhardt, G. & Schroeder, J. I. (2004). Microarray expression analyses of Arabidopsis guard cells and isolation of a recessive ABA hypersensitive Protein Phosphatase 2C mutant. Plant Cell 16: 596-615.
Gong, J.I., Waner, D.A., Horie, T., Li, S.L., Horie, R., Abid, K.B. and J.I. Schroeder (2004). Microarray-based rapid cloning of an ion accumulation deletion mutant in Arabidopsis thaliana. Proc. Natl. Acad. Sci.(USA) 101: 15404-15409.
Kwak, J.M., I.C. Mori, Z-M. Pei, N. Leonhardt, M.A. Torres, J.L. Dangl, R.E. Bloom, S. Bodde, J.D.G. Jones and J.I. Schroeder. (2003). NADPH oxidase AtrbohD and AtrbohF genes function in ROS-dependent ABA signaling in Arabidopsis. EMBO J. 22: 2623-2633.
Gong, J-M., D.A. Lee and J.I. Schroeder. (2003). Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis. Proc. Natl. Acad. Sci. USA 100: 10118-10123.
Lahner, B, J. Gong, M. Mahmoudian, E.L. Smith, K.B. Abid, E.E. Rogers, M.L. Guerinot, J.F. Harper, J.M. Ward, L. McIntyre, J.I. Schroeder and D.E. Salt. (2003). Genomic scale profiling of nutrient and trace elements in Arabidopsis thaliana. Nature Biotechnology 21: 1215-1221.
Kwak, J.M., J-H. Moon, Y. Murata, K. Kuchitsu, N. Leonhardt, A. DeLong and J.I. Schroeder. (2002). Disruption of a guard cell-expressed protein phosphatase 2A regulatory subunit, RCN1, confers abscisic acid insensitivity in Arabidopsis. Plant Cell 14:2849-2861.
Mäser, P., Y. Hosoo, S. Goshima, T. Horie, B. Eckelman, K. Yamada, K. Yoshida, E.P. Bakker, A. Shinmyo, Soiki, J.I. Schroeder, and N. Uozumi (2002). Glycine residues in potassium channel-like selectivity filters determine potassium selectivity in four-loop-per-subunit HKT transporters from plants. Proc. Nat. Acad. Sci. USA, 99:6428-6433.
Hugouvieux, V., J.M. Kwak and J.I. Schroeder. (2001). A mRNA cap binding protein, ABH1, modulates early abscisic acid signal transduction in Arabidopsis. Cell 106: 477-487.
Allen, G.J., S.P. Chu, C.L. Harrington, K. Schumacher, T. Hoffmann, Y.Y. Tang, E. Grill and J.I. Schroeder. (2001). A defined range of guard cell calcium oscillation parameters encodes stomatal movements. Nature. 411: 1053-1057.
Schroeder, J.I., J.M. Kwak. and G.J. Allen. (2001). Guard cell abscisic acid signalling and engineering of drought hardiness in plants. Nature 410: 327-330.
Allen, G.J., Chu, S.P., Schumacher, K., Shimazaki, C.T., Vafeados, D., Kemper, A., Hawke, S.D., Tallman, G., Tsien, R.Y., Harper, J.F., Chory, J. and Schroeder, J.I. (2000). Alteration of Stimulus Specific Guard Cell Calcium Oscillations and Stomatal Closing in Arabidopsis det3 Mutant. Science 289: 2338-2342.
Pei, Z-M., Murata, Y., Benning, G., Thomine, S., Klüsener, B., Allen, G., Grill, E., and Schroeder, J.I. (2000). Calcium channels activated by hydrogen peroxide mediate abscisic acid signalling in guard cells. Nature. 406: 731-734.
Clemens, S., E.J. Kim, D. Neumann and J.I. Schroeder. (1999). Tolerance to toxic metals by a gene family of phytochelatin synthases from plants and yeast. EMBO J. 18:3325-3333.
Clemens, S., Antosiewicz, D.M., Ward, J.M., Schachtman, D.P. and Schroeder, J.I. (1998) The plant cDNA LCT1 mediates the uptake of calcium and cadmium in yeast. Proc. Natl. Acad. Sci. (USA) 95:12043-12048.
Pei, Z-M., Ghassemian, M., Kwak, C.M., McCourt, P. and Schroeder, J.I. (1998) Role of farnesyltransferase in ABA regulation of guard cell anion channels and plant water loss. Science 282: 287-290.
Hildebrand, M., Volcani, B.E., Gassmann, W. and Schroeder, J.I. (1997) A gene family of silicon transporters. Nature 385:688-689.
Pei, Z.M., Kuchitsu, K., Ward, J.M., Schwarz, M. and Schroeder, J.I. (1997) Differential abscisic acid regulation of guard cell slow anion channels in Arabidopsis wild-type and abi1 and abi2 mutants. Plant Cell 9:409-423.
Pei, Z.M., Ward, J.M., Harper, J.F. and Schroeder, J.I. (1996) A novel chloride channel in Vicia faba guard cell vacuoles activated by the serine threonine kinase CDPK. EMBO J. 15:6564-6574.
Rubio, F., Gassmann, W. and Schroeder, J.I. (1995). Sodium-driven potassium uptake by the plant potassium transporter HKT1 and mutations conferring salt tolerance. Science 270:1660-1663.
Schachtman, D.P. and Schroeder, J.I. (1994). Structure and transport mechanism of a high-affinity K+ uptake transporter from higher plants. Nature 370:655-658.
Julian Schroeder received his Ph.D. from the Max-Planck-Institut for Biophysical Chemistry and the University of Göttingen. He is the holder of the Novartis Chair in Plant Sciences at UCSD. He was a postdoctoral fellow of the von Humboldt Foundation at UCLA School of Medicine and is the recipient of an NSF Presidential Young Investigator Award, the Charles Albert Shull Award from the American Society of Plant Physiologists and the 2001 Blasker Award in Environmental Science and Engineering from the S.D. Foundation.
