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
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 and is AAAS Fellow (2006)
Ward, J.M., Maser, P., Schroeder, J.I. Plant Ion Channels: Gene Families, Physiology, and Functional Genomics Analyses. Annual Reviews of Physiology 71: (2009).
Vahisalu, T., Kollist, H., Wang, Y.-F., Nishimura, N., Chan, W.-Y., Valerio, G., Lamminmaki, A., Brosche, M., Moldau, H., Desikan, R., Schroeder, J.I., Kangasjarvi, J. SLAC1 is required for plant guard cell S-type anion channel function in stomatal signalling Nature 452:487-91 (2008).
Mendoza-Cozatl DG, Butko E, Springer F, Torpey JW, Komives EA, Kehr J, Schroeder JI. Identification of high levels of phytochelatins, glutathione and cadmium in the phloem sap of Brassica napus. A role for thiol-peptides in the long-distance transport of cadmium and the effect of cadmium on iron translocation. Plant Journal 54: 249-59 (2008).
Boisson-Dernier, A., Frietsch, S., Kim, T.H., Dizon, M.B. & Schroeder, J.I. The peroxin ABSTINENCE BY MUTUAL CONSENT disrupts male-female gametophyte recognition. Current Biology 18: 63-68 (2008).
Yang Y, Costa A, Leonhardt N, Siegel RS, Schroeder JI. Isolation of a strong Arabidopsis guard cell promoter and its potential as a research tool. Plant Methods. 4: 1-15 (2008).
Imaizumi, T., Kay, S., Schroeder, J.I. Daily watch on Metabolism. Science 318: 1730-1731 (2007).
Horie, T., Costa, A., Kim, TH, Han, MH, Horie, R., Leung, HY, Miyao, A., Hirochika, H., An, G. and Schroeder, J.I. Rice OsHKT2;1 transporter mediates large Na+ influx component into K+-starved roots for growth. EMBO J. 26: 3003-3014 (2007).
Suh, S.J., Wang, Y.F., Frelet, A., Leonhardt, N., Klein, M., Forestier, C., Mueller-Roeber, B., Cho, M.H., Martinoia, E., Schroeder, J.I. The ATP Binding Cassette Transporter AtMRP5 Modulates Anion and Calcium Channel Activities in Arabidopsis Guard Cells. J Biol Chem 282: 1916-1924 (2007).
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. 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 (2006).
Schroeder, J.I., Nambara, E. A quick release mechanism for abscisic acid. Cell 126: 1023-1025 (2006).
Young, J.J., Mehta, S., Israelsson, M., Godoski, J., Grill, E., Schroeder, J.I. 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 (2006).
Schroeder, J.I. Physiology: nitrate at the ion exchange. Nature 442: 877-878 (2006).
Hashimoto, M., Negi, J., Young, J., Israelsson, M., Schroeder, J.I., Iba, K. Arabidopsis HT1 kinase controls stomatal movements in response to CO2. Nature Cell Biol. 8: 391-397 (2006).
Sunarpi, Horie, T., Motoda, J., Kubo, M., Yang, H., Yoda, K., Horie, R., Chan, W.Y., Leung, H.Y., Hattori, K., Konomi, M., Osumi, M., Yamagami, M., Schroeder, J.I., Uozumi, N. Enhanced salt tolerance mediated by AtHKT1 transporter-induced Na unloading from xylem vessels to xylem parenchyma cells. Plant J. 44: 928-938 (2005).
Colcombet, J., Boisson-Dernier, A., Ros-Palau, R., Vera, C.E., Schroeder, J.I. Arabidopsis somatic embryogenesis receptor kinases 1 and 2 are essential for tapetum development and microspore maturation. Plant Cell 17: 3350-3361 (2005).
Gierth, M., Mäser, P., Schroeder, J.I. The Potassium Transporter AtHAK5 Functions in K+ Deprivation-Induced High-Affinity K+ Uptake and AKT1 K+ Channel Contribution to K+ Uptake Kinetics in Arabidopsis Roots. Plant Physiology 137: 1105-1114 (2005).
Leonhardt, N., Kwak, J. M., Robert, N., Waner, D., Leonhardt, G. & Schroeder, J. I. Microarray expression analyses of Arabidopsis guard cells and isolation of a recessive ABA hypersensitive Protein Phosphatase 2C mutant. Plant Cell 16: 596-615 (2004).
Mäser, P., Leonhardt, N. & Schroeder, J. I. The Clickable Guard Cell: Electronically Linked Model of Guard Cell Signal Transduction Pathways. The Arabidopsis Book (access: http://www.bioone.org/bioone/?request=get-document&issn=1543-8120&volume=032&issue=01&page=0001). Editors: C. Sommerville and E. Meyerowitz. Publisher: Amer. Soc. Plant Biol., 1-4 (2003).
Lahner, B, J. M. 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. Genomic scale profiling of nutrient and trace elements in Arabidopsis thaliana. Nature Biotechnology 21: 1215-1221 (2003).
Gong, J-M., D.A. Lee and J.I. Schroeder. Long-distance root-to-shoot transport of phytochelatins and cadmium in Arabidopsis. Proc. Natl. Acad. Sci. USA 100: 10118-10123 (2003).
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. NADPH oxidase AtrbohD and AtrbohF genes function in ROS-dependent ABA signaling in Arabidopsis. EMBO J. 22: 2623-2633 (2003).
Kwak, J.M., J-H. Moon, Y. Murata, K. Kuchitsu, N. Leonhardt, A. DeLong and J.I. Schroeder. Disruption of a guard cell-expressed protein phosphatase 2A regulatory subunit, RCN1, confers abscisic acid insensitivity in Arabidopsis. Plant Cell 14:2849-2861 (2002).
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. 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 (2002).
Hugouvieux, V., J.M. Kwak and J.I. Schroeder. A mRNA cap binding protein, ABH1, modulates early abscisic acid signal transductuion in Arabidopsis. Cell 106: 477-487 (2001).
Allen, G.J. and J.I. Schroeder. Combining genetics and cell biology to crack the code of plant cell calcium signaling. Science STKE (2001).
Schroeder, J.I., J.M. Kwak. and G.J. Allen. Guard cell abscisic acid signalling and engineering of drought hardiness in plants. Nature 410: 327-330 (2001).
Allen, G.J., S.P. Chu, C.L. Harrington, K. Schumacher, T. Hoffmann, Y.Y. Tang, E. Grill and J.I. Schroeder. A defined range of guard cell calcium oscillation parameters encodes stomatal movements. Nature 411: 1053-1057 (2001).
Allen, G.J., S.P. Chu, K. Schumacher, C.T. Shimazaki, D. Vafeados, A. Kemper, S.D. Hawke, G. Tallman, R.Y. Tsien, J.F. Harper, J. Chory and J.I. Schroeder. Alteration of stimulus specific guard cell calcium oscillations and stomatal closing in Arabidopsis det3 mutant. Science 289: 2338-2342 (2000).
Pei, Z-M., Y. Murata, G. Benning, S. Thomine, B. Klüsener, G. Allen, E. Grill and J.I. Schroeder. Calcium channels activated by hydrogen peroxide mediate abscisic acid signalling in guard cells. Nature 406: 731-734 (2000).
Thomine, S., Wang, R., Ward, J.M., Crawford, N.M., and Schroeder, J.I. Cadmium and iron transport by members of a plant metal transporter family in Arabidopsis with homology to Nramp genes. Proc. Natl. Acad. Sci. USA 97:4991-4996 (2000).
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.
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., 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.
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., 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.