The goal of the proposed research is to determine how higher plants signal the arrest of a critical developmental pathway in the reproductive cycle. The experimental system is that of receptor- mediated signalling in the self-incompatibility response of Brassica, a genetically controlled self recognition system that prevents self- fertilization by arresting the development of genetically related pollen grains. Our cloning and characterization in 1991 of the receptor serine/threonine kinase that mediates this self-recognition, soon after the description in 1990 of the first member of the TGF-beta class of receptors with serine/threonine specificity, represented an important advance in our understanding of self-incompatibility and of cell-cell communication in plants. Our recent identification of a gene with sequence similarity to aquaporins (water channels) as an effector of receptor-mediated signalling in this system provides the first molecular evidence relating to the mechanism by which the activation and development of pollen is arrested. We propose to characterize this water channel, its cellular and subcellular distribution in plant cells, define its biophysical and biochemical properties, and determine its role in the arrest of pollen. In addition, we plan to identify other components of signal transduction in this system and construct a biochemical pathway that links the signalling receptor to activation of its putative downstream target, the water channel. When considered in light of work on receptors and water channels in hormone-induced activation of osmotic water permeability in mammalian cells, this study should provide for an informative comparison of the mechanisms by which the regulation of transcellular water transfer is achieved in organisms as divergent as plants and mammals.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Molecular Cytology Study Section (CTY)
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Shapiro, Bert I
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Cornell University
Other Basic Sciences
Schools of Earth Sciences/Natur
United States
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Tantikanjana, Titima; Rizvi, Noreen; Nasrallah, Mikhail E et al. (2009) A dual role for the S-locus receptor kinase in self-incompatibility and pistil development revealed by an Arabidopsis rdr6 mutation. Plant Cell 21:2642-54
Boggs, Nathan A; Dwyer, Kathleen G; Nasrallah, Mikhail E et al. (2009) In vivo detection of residues required for ligand-selective activation of the S-locus receptor in Arabidopsis. Curr Biol 19:786-91
Liu, Pei; Sherman-Broyles, Susan; Nasrallah, Mikhail E et al. (2007) A cryptic modifier causing transient self-incompatibility in Arabidopsis thaliana. Curr Biol 17:734-40
Naithani, Sushma; Chookajorn, Thanat; Ripoll, Daniel R et al. (2007) Structural modules for receptor dimerization in the S-locus receptor kinase extracellular domain. Proc Natl Acad Sci U S A 104:12211-6
Nasrallah, June B (2005) Recognition and rejection of self in plant self-incompatibility: comparisons to animal histocompatibility. Trends Immunol 26:412-8
Sainudiin, Raazesh; Wong, Wendy Shuk Wan; Yogeeswaran, Krithika et al. (2005) Detecting site-specific physicochemical selective pressures: applications to the Class I HLA of the human major histocompatibility complex and the SRK of the plant sporophytic self-incompatibility system. J Mol Evol 60:315-26
Chookajorn, Thanat; Kachroo, Aardra; Ripoll, Daniel R et al. (2004) Specificity determinants and diversification of the Brassica self-incompatibility pollen ligand. Proc Natl Acad Sci U S A 101:911-7
Nasrallah, Mikhail E; Liu, Pei; Nasrallah, June B (2002) Generation of self-incompatible Arabidopsis thaliana by transfer of two S locus genes from A. lyrata. Science 297:247-9
Kachroo, A; Schopfer, C R; Nasrallah, M E et al. (2001) Allele-specific receptor-ligand interactions in Brassica self-incompatibility. Science 293:1824-6
Dixit, R; Nasrallah, M E; Nasrallah, J B (2000) Post-transcriptional maturation of the S receptor kinase of Brassica correlates with co-expression of the S-locus glycoprotein in the stigmas of two Brassica strains and in transgenic tobacco plants. Plant Physiol 124:297-311

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