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This project aims at understanding the mechanisms allowing plant cells to orient themselves within a tissue to acquire their identity and functionality. Cell polarity is essential for cell differentiation, plant development and nutrition. Proteins polarly localized are typically involved in nutrients or hormones transport, allowing a directional flux of molecules necessary for their uptake or their gradual distribution within a tissue or organ. Plant cells maintain such an asymmetric localization of proteins by means of targeted secretion and endocytosis and by locally reducing lateral diffusion in the membrane. Molecular mechanisms regulating cell polarity, either intrinsic in the protein sequence (and its post-translational modifications) or extrinsic in the lipidic environment, are still poorly understood. The objectives of this project will be to identify new regulators of cell polarity in the root epidermis and endodermis through a high-throughput genetic screen on novel polarity sensors. These sensors are based on a split-luciferase system fused to proteins being able to interact but with a developmentally regulated polarity. One sensor has already been developed to detect sensitive changes in apico-basal polarity in the root epidermal cells and will serve as a starting point for a forward genetic screen aimed at isolating mutants affected in apical-basal polarity in epidermal root cells. A similar sensor will be adapted during the course of this project to endodermal cells that display a proximo-distal polarity with a specific role of the diffusion barrier formed by the casparian strips. The identification of mutants affecting the polarity of those two sensors will improve our understanding of the mechanisms required for establishment and maintenance of cell polarity in root epidermal and endodermal cells, two tissues playing a crucial role for plant development and nutrition.
I graduated from Paris-Sud University in December 2006 with a PhD in Plant Biology. My thesis, supervised by Herman Höfte (INRA Versailles), focused on the characterization of a putative cell-wall integrity sensor in Arabidopsis. I further studied cell wall biosynthesis and response to pathogens during a postdoctoral training in the laboratories of Chris and Shauna Somerville in Stanford and Berkeley (2007-2009). After a short postdoctoral return at INRA, I obtained in 2010 a permanent position as INRA research scientist in the team of Jean-Denis Faure in Versailles. In the past five years I studied the role of lipid biosynthesis and cell polarity during cell differentiation. During my AgreenSkills fellowship in Geldner laboratory at the University of Lausanne, I studied mutants impaired in polar localization of various proteins of the root epidermis or endodermis.
Kalmbach L, Hématy K, De Bellis D, Barberon M, Fujita S, Ursache R, Daraspe J, Geldner N, 2017. Transient cell-specific EXO70A1 activity in the CASP domain and Casparian strip localization. Nature Plants. 24;3:17058. Doi:10.1038/nplants.
Hématy, K, Bellec, Y., Podicheti, R., et al., 2016. The zinc-finger protein SOP1 is required for a subset of the nuclear exosome functions in Arabidopsis. PLoS Genetics 12(2):e1005817. Doi: 10.1371/journal.pgen.1005817.
Anne, P., Azzopardi, M., Gissot, L., Beaubiat, S., Hématy, K, Palauqui J.C., 2015. OCTOPUS negatively regulates BIN2 to control phloem differentiation in Arabidopsis. Current Biology 25(19), 2584-90.
Wolf, S., Hématy, K, Höfte, H., 2012. Growth Control and Cell Wall Signaling in Plants. Annual Review of Plant Biology, 63, 381-407.
Markham, J. E., Molino, D., Gissot, L., Bellec, Y., Hématy, K., Marion, J., Belcram, K., Palauqui, J.-C., Satiat-JeuneMaitre, B., Faure, J. D., 2011. Sphingolipids containing very-longchain fatty acids define a secretory pathway for specific polar plasma membrane protein targeting in Arabidopsis. Plant Cell, 23 (6), 2362-2378.