Brassinosteroid signal transduction and proteomics We are interested in how hormonal and environmental signals regulate plant growth and development. Our research focuses on (1) the brassinosteroid (BR) signal transduction pathway in the model plant system Arabidopsis thaliana, and (2) proteomic study of signal transduction. We use a combination of multiple approaches in our research to gain a comprehensive understanding of the biological system and to provide inter-disciplinary training to students and postdocs.
Brassinosteroid is a plant growth hormone	The brassinosteroid signal transduction pathway
BRs are plant steroid hormones that regulate a wide range of developmental and physiological processes, including cell elongation, cell division, stem elongation, vascular differentiation, senescence, and photomorphogenesis. BR deficient mutants, such as det2, show dramatic developmental alterations that include dwarfism, male sterility, delayed flowering, reduced apical dominance, and development of light-grown morphology in the dark. Studies in the last decade have established the BR pathway as one of the best-studied signal transduction pathways in plants. However, little is known about how BR signaling regulates various developmental and physiological processes. BRs are perceived by the cell-surface receptor kinase BRI1. BRs bind to the extracellular domain of BRI1 and activate BRI1’s kinase activity, initiating a signal transduction cascade that leads to nuclear gene expression and cellular responses. Another receptor kinase, BAK1, interacts with and is activated by BRI1 upon BR binding. BR response is negatively regulated by the GSK3-like kinase BIN2 and positively regulated by the nuclear proteins BZR1 and its homolog BZR2/BES1. In the absence of BRs, BIN2 phosphorylates BZR1 and BZR2 at multiple residues, and phosphorylation inhibits the transcription factors through multiple mechanisms, including degradation by the proteasome, cytoplasmic retention by the 14-3-3 proteins, and inhibiting DNA binding. BR treatment causes dephosphorylation and activation of the BZR1 and BZR2 proteins, most likely by inhibiting BIN2 or activating a phosphatase such as BSU1. BZR1 and its homologs are novel transcription factors that bind specifically to the BR response element (BRRE) and regulate BR responsive gene expression. Our Current research focuses on the following areas: (1) functional study of proteins that interact with known BR signaling proteins, such as BZR1, which have been identified by yeast two-hybrid screen and tandem affinity purification; (2) Genomic study of BZR1 target genes using chromatin immunoprecipitation-microarray and systems biology study of the BR regulatory pathway; (3) Molecular genetic studies of BR functions in specific plant developmental processes; (4) Proteomic studies of new BR signal transduction components; (5) Biochemical and cell biological studies of BR signaling mechanisms; (6) Proteomic studies of other signaling pathways that reglate plant growth and development. We have performed proteomic studies of the BR-signaling pathway using two-dimensional difference gel electrophoresis (2-D DIGE) and mass spectrometry. The improved 2-D DIGE method allows accurate comparison of thousands of protein forms between biological samples. We have identified large numbers of BR-regulated proteins, which include known and novel BR signaling proteins, as well as proteins that mediate downstream growth responses. The results of genetic, genomic, and proteomic approaches have overlapped to provide mutual confirmation. A clear picture is emerging to show how BR signal is transduced from the cell surface receptor kinase to nuclear transcription factors and how transcriptional control by BZR1 modulates other pathways and regulate specific cellular and developmental processes. The powerful proteomic methods are now used in the lab and through collaborations to dissect additional signal transduction pathways that regulate plant growth.
Identification of Brassinosteroid regulated proteins(left) and plasma membrane proteins(right) using 2-D DIGE Proteins of BR treated and untreated Arabidopsis were labeled with Cy3 and Cy5 dyes and separate by two-dimensional gel electrophoresis.

Group members:

• Zhiyong Wang (PI)
• Zhiping Deng, PDRA
• Joshua Gendron, Graduate student
• Tae-Wuk Kim, PDRA
• Yu Sun, PDRA
• Wenqiang Tang, PDRA
• Sunita Patil, M.S. student
• Ruiju Wang, visiting student
• Ulrich Kutschera, visiting professor (http://www.uni-kassel.de/fb19/plantphysiology/)
• Shengwei Zhu, visiting scientist

Alumni:

• Junxian He, Monsanto Inc
• Soo-Hwan Kim, Assistant Professor, Yonsei University, Korea
• Srinivas Gampala, Edenspace, Kansas
• Ying Sun, Professor, Hebei Normal University, China
• Rachana Ajay Kumar, Graduate student, U. Washington

Selected Publications:

1. Zhiping Deng, Xin Zhang, Wenqiang Tang, Juan A Oses-Prieto, Nagi Suzuki, Joshua M Gendron, Huanjing Chen, Shenheng Guan, Robert J. Chalkley, T. Kaye Peterman, Alma L. Burlingame, and Zhi-Yong Wang. A Proteomic Study of Brassinosteroid Response in Arabidopsis. Molecular Cellular Proteomics, in press.
2. Joshua M. Gendron and Zhi-Yong Wang (2007). Multiple mechanisms modulate Brassinosteroid signaling. Current Opinion in Plant Biology, 10, 436-441.
3. Srinivas S. Gampala, Tae-Wuk Kim, Jun-Xian He, Wenqiang Tang, Zhiping Deng, Ming-Yi Bai, Shenheng Guan, Sylvie Lalonde, Ying Sun, Joshua M. Gendron, Huanjing Chen, Nakako Shibagaki, Robert J. Ferl, David Ehrhardt, Kang Chong, Alma L. Burlingame, and Zhi-Yong Wang (2007). An Essential Role for 14-3-3 Proteins in Brassinosteroid Signal Transduction in Arabidopsis. Developmental Cell 13, 177-189
4. Ming-Yi Bai, Li-Ying Zhang, Srinivas S. Gampala, Sheng-Wei Zhu, Wen-Yuan Song, Kang Chong, and Zhi-Yong Wang (2007). Functions of OsBZR1 and 14-3-3 proteins in brassinosteroid signaling in rice. Proc Nat Acad Sci 104, 13839-44
5. Zhang X, Chen Y, Wang ZY, Chen Z, Gu H, Qu LJ. (2007) Constitutive expression of CIR1 (RVE2) affects several circadian-regulated processes and seed germination in Arabidopsis. The Plant Journal, 51(3), 512-525
6. Wang ZY, Wang Q, Chong K, Wang F, Wang L, Bai M, Jia C. (2006). The brassinosteroid signal transduction pathway. Cell Res. 16(5): 427-34.
7. Shi, Y-H., Zhu, S-W., Mao, X-Z., Feng, J-X., Zhang, L., Cheng, J., Wei, L-P., Wang, Z-Y., Zhu, Y-X. (2006) Transcriptome Profiling, Molecular Biological and Physiological Studies Reveal a Major Role for Ethylene in Cotton Fiber Cell Elongation. Plant Cell, in press.
8. He, J-X., Gendron, J. M., Sun, Y., Gampala, S. S. L., Gendron, N., Sun, C. Q. and Wang, Z-Y. (2005). BZR1 is a transcriptional repressor with dual roles in brassinosteroid homeostasis and growth responses. Science 307, 1634-1638.
9. Wang Z-Y and He, J-X. (2004). Brassinosteroid signal transduction: choices of signals and receptors. Trends in Plant Science 9 (2), 91-96.
10. He, J-X., Gendron, J. M., Yang, Y. Li, J., Wang, Z-Y. (2002). The GSK3-like kinase BIN2 phosphorylates and destabilizes BZR1, a positive regulator of the brassinosteroid signaling pathway in Arabidopsis. Proc. Nat. Acad. Sci, 99, 10185-10990.
11. Wang, Z-Y., Nakano, T., Gendron, J. M., He, J., Chen, M., Vafeados, D., Yang, Y., Fujioka, S, Yoshida, S., Asami, T., Chory, J. (2002). Nuclear-localized BZR1 mediates brassinosteroid-induced growth and feedback suppression of brassinosteroid biosynthesis. Dev. Cell, 2, 505-513.
12. Wang, Z-Y., Setu, H., Fujioka, S., Yoshida, S., and Chory, J. (2001). BRI1 is a critical component of a plasma membrane receptor for plant steroids. Nature, 410, 380-382.
13. He, Z., Wang, Z-Y., Li, J., Zhu, Q., Lamb, C., Ronald, P., and Chory, J. (2000) Perception of brassinosteroids by the extracellular domain of the receptor kinase BRI1. Science, 288, 2360-3
14. Wang, Z-Y, Tobin, E. M. (1998). Constitutive expression of the CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) gene disrupts circadian rhythms and suppresses its own expression. Cell 93, 1207-1217.
15. Wang, Z-Y., Kenigsbuch, D., Sun, L., Harel, E., Ong, M.S., Tobin, E.M. (1997). A Myb-related transcription factor is involved in the phytochrome regulation of an Arabidopsis Lhcb gene. Plant Cell 9, 491-507.