The goal of the proposed research is to understand how cell-cell recognition signals the arrest of a critical developmental pathway in the reproductive phase of the plant's life cycle. Our experimental system is the self-incompatibility response of crucifers, which is an ultra-specific mating barrier that prevents self-fertilization by arresting the development of genetically related """"""""self"""""""" pollen grains. The recognition of self in this system is based on the activity of highly diverged alleles of a transmembrane receptor protein kinase and its defensin-like peptide ligand, which are the female and male determinants of specificity, respectively. We plan to extend research during the current funding period, which identified and described several characteristics of the ligand, and demonstrated that specificity in the self-incompatibility response is based on allele-specific receptor-ligand interactions. We propose to perform structure-activity relationship studies of receptor and ligand with the goal of mapping domains that determine specificity in their interaction and in activation of the pollen-inhibitory signal transduction pathway. We also plan to investigate the self-incompatibility signal transduction pathway using molecular genetic and proteomics approaches. The intra-specific divergence of these receptor-ligand pairs exceeds the inter-specific divergence typical of many reproductive proteins, such as mammalian proteins that function in species-specific sperm-egg interaction. Also like other self/nonself recognition molecules, the SI proteins are subject to diversifying selection and must co-evolve to maintain their specific interaction. Because the two interacting partners in SI recognition are known, and a large number of natural receptor-ligand variants are available for study, the SI system of crucifers is ideally suited for exploring the structural basis of specific receptor-ligand interactions and for gaining insight into the co-evolution of gene functions that typically underlies recognition phenomena.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Cell Development and Function Integrated Review Group (CDF)
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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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