Joanne Chory
e-mail: chory@salk.edu |
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Light signals are required for the induction and regulation of many developmental processes in plants. Light signals initiate cotyledon expansion and leaf development, and cause the inhibition of stem growth. At the molecular level, light induces gene expression regulating chloroplast development. At later stages in the life cycle, light quality can influence the plant's growth habit and allow it to grow above a shade source, possibly an adaptation to avoid competition for light. In addition to these developmental responses to light, plants also utilize information from their light environment to determine the length of day, the time of day, and their geographical location. Several regulatory photoreceptors are involved in the perception of light signals; however, the exact mechanisms by which photons are perceived by plant cells and used to regulate physiological responses are not understood.
We are dissecting this process using molecular genetics and genomics in the small cruciferous plant, Arabidopsis. The genetic analysis indicates that light responses are not simply endpoints of linear signal transduction pathways, but are the result of the integration of information from a variety of photoreceptors acting through a complex network of interacting signaling components. Using either forward genetic screens or biochemical analysis coupled with reverse genetics approaches, our lab and others have identified approximately 50 Arabidopsis genes that play a role in this signal transduction network. We have shown that signaling by the red/far-red photoreceptor, phytochrome, involves phosphorylation/dephosphorylation, and we have begun to characterize proteins that are involved in the regulation of phytochrome's subcellular location in response to light. Our studies have also revealed that steroid hormones and auxin are involved in light-regulated development. We have identified the plant steroid receptor, a plasma membrane localized receptor kinase with serine/threonine specificity, as well as characterized several components in the signaling pathway that link recognition of the steroid at the cell surface to changes in gene expression in the nucleus. More recently, we have begun to investigate the interactions of auxin with both the light and brassinosteroid pathways. Our current studies are focused on understanding the mechanistic links of the photoreceptor signaling pathways with endogenous developmental pathways that involve the action of plant hormones.
Fankhauser, C., K.-C. Yeh, J.C. Lagarias, H. Zhang, T.D. Elich, and J. Chory. (1999). PKS1, a substrate phosphorylated by phytochrome that modulates light signaling in Arabidopsis. Science. 284: 1539-1541.
S. Christensen, N. Dagenais, J. Chory, and D. Weigel. (2000). Regulation of auxin response by the protein kinase PINOID. Cell 100: 469-478.
He, Z., Z. Wang, J. Li, Q. Zhu, C. Lamb, P. Ronald, and J. Chory. (2000). Perception of brassinosteroids by the extracellular domain of the receptor kinase, BRI1. Science. 288: 2360-2363.
Zhao, Y., S. Christensen, C. Fankhauser, J. Cashman, J. Cohen, D. Weigel, and J. Chory. (2001). A role for flavin monooxygenase-like enzymes in auxin biosynthesis. Science. 291: 306-309.
Wang, Z.-Y., H. Seto, S. Fujioka, S. Yoshida, and J. Chory. (2001). BRI1 is a critical component of a plasma membrane receptor for plant steroids. Nature. 410: 380-383.
Maloof, J.N., J.O. Borevitz, T. Dabi, J. Lutes, R. Nehring, J. Redfern, G. Trainer, J. Wilson, T. Asami, C. C. Berry, D. Weigel, and J. Chory. (2001). Natural variation in light sensitivity in Arabidopsis. Nature Genetics. 29: 441-446.
Borevitz, J.O., J. N. Maloof, J. Lutes, T. Dabi, J.L. Redfern, G.T. Trainer, J.D. Werner, T. Asami, C. C. Berry, D. Weigel, and J. Chory. (2002). Quantitative trait loci controlling light and hormone response in two accessions of Arabidopsis thaliana. Genetics. 160: 683-696.
Yin, Y., Z.-Y. Wang, S. Mora-Garcia, J. Li, S. Yoshida, T. Asami, and J. Chory. (2002). BES1 accumulates in the nucleus in response to brassinosteroids to regulate gene expression and promote stem elongation. Cell. 109: 181-191.
Hu, J., M. Aguirre, C. Peto, J. Alonso, J. Ecker, and J. Chory. (2002). A role for peroxisomes in photomorphogenesis and development of Arabidopsis. Science. 297: 405-409.
Schroeder, D., M. Gahrtz, B. Maxwell, R.K. Cook, J. Kan, J. Alonso, J. Ecker, and J. Chory. (2002). De-etiolated 1 (DET1) and damaged DNA binding protein 1 (DDB1) interact to regulate Arabidopsis photomorphogenesis. Curr. Biol. 12: 1462-1472.
Strand, Å, T. Asami, J. Alonso, J. Ecker, and J. Chory. (2002). Chloroplast to nucleus communication triggered by Mg-protoporphyrin IX accumulation. Nature. In press.
Joanne Chory received her Ph.D from the U. of Illinois and was a postdoctoral fellow at Harvard Medical School. She is an investigator with the Howard Hughes Medical Institute, a member of the U.S. National Academy of Sciences, and a fellow of the American Academy of Arts and Sciences.
