Progress 10/01/99 to 09/30/04
Outputs
The goal of this project was to understand the role of Rop GTPases in plant signal transduction in the regulation of plant growth, development and defense/stress responses. We completed all the major objectives as summarized below: 1) We have identified a ROP-mediated molecular network that controls pollen tube growth, a process critical for pollination. 2) Using transgenic Arabidopsis plants expressing constitutively active (CA) and dominant negative (DN) mutant of ROP2, we have demonstrated that Rop signaling controls many aspects of plant growth and development. 3) We have shown that ROPs control different stages of root hair development including hair initiation and elongation. 4) W have demonstrated that ROPs have a general role in the regulation of cell shape formation in various cell types and does so by regulating the localized accumulation of cortical F-actin. 5) We have shown that ROPs regulate the sensing of imbalanced carbon:nitrogen ratios 6) ROPs are
negative regulators of ABA signaling. 7) We identified a family of Rop-interacting proteins, termed RICs (Rop-interactive CRIB motif containing proteins). Arabidopsis contains 11 RICs. Functional analysis using transient expression in pollen tubes suggests that different RICs may act as Rop targets to control specific signaling pathways.
Impacts
The results obtained from this project will provide a better understanding at the level how plant growth, development and responses to the environment is controlled. This knowledge may be useful for genetically engineering plants (especially crop plants) that have improved productivity and tolerance to environmental stresses. For example, transgenic expression of ROP mutants may be used to promote root hair formation for improving the capacity of plants to uptake nutrients and water from the soil, to enhance ABA responses for improving tolerance to drought stress, and to increase the capacity of plants to handle imbalanced high ratio of C:N in order to minimize the use of nitrogen fertilizers thereby reducing soil pollution.
Publications
- Bao, F., J. Shen, S. R. Brady, G. K. Muday, T. Asami, Z. Yang. 2004. Brassinosteroids interact with auxin to promote lateral root development in Arabidopsis. Plant Physiol. 134: 1624-1631.
- Park, J., Y. Gu, Y. Lee, Z. Yang, and Y. Lee. 2004. Phosphatidic acid induces leaf cell death in Arabidopsis by activating the Rho-related small G protein GTPase-mediated pathway of reactive oxygen species generation. Plant Physiol. 134: 129-136.
- Yang, Z. 2003. GABA, a new player in the plant mating game. Developmental Cell 5:185-186.
- Li, S., L. Blanchoin, Z. Yang, and E. M. Lord. 2003. The putative Arabidopsis Arp2/3 complex controls leaf cell morphogenesis. Plant Physiol. 132: 2034-2044.
- Vernoud, V., A.C. Horton, Z. Yang, and E. Nielson. 2003. Analysis of the small GTPase gene family of Arabidopsis thaliana. Plant Physiol. 131: 1191-1208.
- Gu, Y., V. Vernoud, Y. Fu, and Z. Yang. 2003. ROP GTPase regulation of pollen tube growth through the dynamics of tip-localized F-actin. J. Exp. Bot. 54: 93-101.
- Zheng, Z.-L., M. Nafisi, H. Li, A. Tam, D.N. Crowell, S.N. Chary, J. Shen, J. I. Schroeder, and Z.Yang. 2002. The Arabidopsis small GTPase ROP10 is a specific negative regulator of phytohormone abscisic acid ABA responses. Plant Cell. 14: 2787-2797
- Baxter-Burrel, A., Z. Yang, P. Springer, and J. Bailey-Serres. 2002. RopGAP4-dependent Rop GTPase rheostat controls Arabidopsis oxygen deprivation tolerance. Science. 296:2026-2028.
- Yang, Z. 2002. Small GTPases: Versatile Signaling Switches in Plants. Plant Cell 14: S375-S388.
- Fu, Y., H. Li, and Z. Yang. 2002. The Rop2 GTPase controls the formation of cortical fine F-actin and the early phase of directional cell expansion during Arabidopsis organogenesis. Plant Cell. 14:763-776.
- Jones, M.A. J. Shen , H. Li, Y. Fu, Z. Yang* and C. S. Grierson*. 2002. The Arabidopsis Rop2 GTPase is a positive regulator of both root hair initiation and tip growth. Plant Cell. 14:777-794. *Co-corresponding authors.
- Wu, G., Y. Gu, S. Li, and Z. Yang. 2001. A Genome-wide analysis of Arabidopsis Rop-interactive CRIB motif-containing proteins that act as Rop GTPase targets. Plant Cell. 13:2841-2856.
- Li, H., J. Shen, Z. Zheng, Y. Lin, and Z. Yang. 2001. The Rop GTPase switch controls multiple distinct developmental processes in Arabidopsis. Plant Physiol. 126:670-684.
- Fu, Y. and Z. Yang. 2001. The Rop GTPase: A master switch of cell polarity development in plants. Trends in Plant Science 6:545-547.
- Li, H., J. Shen, Z. Zheng, Y. Lin, and Z. Yang. 2001. The Rop GTPase switch controls multiple distinct developmental processes in Arabidopsis. Plant Physiol. 126:670-684.
- Fu, Y, G. Wu, and Z. Yang. 2001. Rop GTPase-Dependent dynamics of tip-localized F-actin controls tip growth in pollen tubes. J Cell Biol. 152:1019-1032.
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Progress 01/01/01 to 12/31/01
Outputs
The goal of this project is to understand the role of Rop GTPases in plant signal transduction in the regulation of plant growth, development and defense/stress responses. We had made significant progress toward the goal in the following areas in the past year: 1) Using transgenic Arabidopsis plants expressing constitutively active (CA) and dominant negative (DN) mutant of ROP2, we have demonstrated that Rop signaling controls many aspects of plant growth and development. 2) Using CA-rop2 and DN-rop2 mutants, we have shown that Rop2 controls different stages of root hair development including hair initiation and elongation. 3) Using CA-rop2 and DN-rop2 mutants, we have demonstrated that Rop2 has a general role in the regulation of cell shape formation in various cell types and does so by regulating the localized accumulation of cortical F-actin. 4) To understand how Rop signaling modulates different plant processes, we identified a family of Rop-interacting proteins,
termed RICs (Rop-interactive CRIB motif containing proteins). Arabidopsis contains 11 RICs. Functional analysis using transient expression in pollen tubes suggests that different RICs may act as Rop targets to control specific signaling pathways.
Impacts
The results obtained from this project will provide a better understanding at the level how plant growth, development and responses to the environment is controlled. This knowledge may be useful for genetically engineering plants (especially crop plants) that have improved productivity and tolerance to environmental stresses. For example, Rop2 mutants may be used to promote root hair formation to improve the capacity of plants to uptake nutrients and water from the soil.
Publications
- Fu, Y., H. Li, and Z. Yang. 2002. The Rop2 GTPase controls the formation of cortical fine F-actin and the early phase of directional cell expansion during Arabidopsis organogenesis. Plant Cell. In press.
- Jones, M.A. J. Shen , H. Li, Y. Fu, Z. Yang* and C. S. Grierson*. 2002. The Arabidopsis Rop2 GTPase is a positive regulator of both root hair initiation and tip growth. Plant Cell. In press. *Co-corresponding authors.
- Wu, G., Y. Gu, S. Li, and Z. Yang. 2001. A Genome-wide analysis of Arabidopsis Rop-interactive CRIB motif-containing proteins that act as Rop GTPase targets. Plant Cell. 13:2841-2856.
- Li, H., J. Shen, Z. Zheng, Y. Lin, and Z. Yang. 2001. The Rop GTPase switch controls multiple distinct developmental processes in Arabidopsis. Plant Physiol. 126:670-684.
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Progress 01/02/00 to 12/31/00
Outputs
We have achieved three major accomplishments and findings: 1) Identified and characterized a family of Rop GTPase negative regulators, termed Rop GTPase-activating proteins (RopGAPs). This study demonstrates that the plant-specific RopGAPs employs a novel mechanism for the regulation of its activity toward Rop GTPases. 2) Demonstrated that the Rop GTPase acts as a versatile switch to control many distinct processes during plant growth, development, and responses to the environment using a combination of transgenic plants and rop knockout mutants. This work provides evidence that the Rop GTPase participates many distinct signaling pathways and that the genetic manipulation of Rop GTPase genes may prove to be useful for improving plant productivity and tolerance to environmental stresses including water deficiency, nutrient deficiency, and pathogen attacks. 3) Identified and characterized a novel proteins that act as direct Rop targets. This work represents the first
identification of G protein targets in plants.
Impacts
We have identified a series of regulatory genes that are important for modulating plant growth, development, and responses to the environment. Evidence suggests that modification of these genes will prove to be useful for improving plant productivity and tolerance to environmental stresses including water deficiency, nutrient deficiency, and pathogen attacks. The potential long-term impact of this work includes improved agricultural productivity and environments by reducing the utilization of chemicals as pesticides and fertilizers.
Publications
- Fu, Y., Wu, G., and Yang, Z. 2001. Rop GTPase-Dependent dynamics of tip-localized F-actin controls tip growth in pollen tubes. J. Cell Biol. In press.
- Lin, Y., Seals, D.F., Randall, S.K., and Yang, Z. 2001. Dynamic localization of Rop GTPase to the tonoplast during vacuole development. Plant Physiol. In press.
- Wu, G., Li, H., and Yang, Z. 2000. Arabidopsis RopGAPs are a novel family of Rho GTPase-activating proteins that require the Cdc42/Rac-interactive binding motif for Ro-specific GTPase stimulation. Plant Physiol. 124:1625-1636.
- Park, J., Choi, H.-J., Lee, S., Lee, T., Yang, Z., and Lee, Y. 2000. Involvement of a Rac-related GTP-binding protein in elicitor-induced reactive oxygen generation by suspension-cultured soybeans cells. Plant Physiol. 124:725-732
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