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Descrição
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The current proposal deals with the functional characterization of glutamate receptors (GLRs) in cellular polarity, morphogenesis and development of pollen tubes (PTs). GLRs probably evolved from aminoacid sensing peribacterial proteins and are found in almost all clades of the tree of life (1). In humans their role in neuronal transmission is well established, but their role in other cells or organisms is rather scant. They became the subject of much interest in plants upon their description on Arabidopsis(At)(2) and other plants. In rice and grapevine, for e.g., there are about 60 annotated GLRs (3), close to the number found in humans. Yet plants have no nervous system, and most species have no excitable cells. A decade of systematic screening later, their role continued to be elusive (4). We recently proved a role for 2 GLR genes in PT growth and signaling (Michard…Feijó, 2011, Science, 332:434, res.article+cover) establishing GLRs as the first class of genes to code for plasma membrane Ca2+ channels in plants(5). The success behind using PTs may lie in the fact that these cells are so dependent on Ca2+ for growth and signaling. PTs are also an excellent model for cell polarity (6). Here we propose to further investigate the role of GLR’s in PTs, along 4 lines that will focus on a variety of genetic, physiology and evolutionary aspects of GLR function in pollen tubes of Arabidopsis and other species. Such experimental approach will be complemented with the development of mathematical modeling of aspects concerning Ca2+ choreography and the emergence of the pollen as a macroscopic manifestation of signaling mechanisms downstream of Ca2+. Focus is on the pollen tube system, as a paradigm of cell polarity. But multiple KO’s are on target to affect other organs in the plant, that we will screen as well(specially roots). This should enlarge the scope of this proposal to a broader plant context. Increasing our knowledge about plant GLRs will also feed back on other disciplines such as neuro, developmental or evolutionary biology. Most of what we know of GLR’s is focused on the brain and synaptic transmission, but recent studies enlarged that to unforeseen roles of ionotropic GLRs (for e.g. their possible role as receptors in odour perception in insects, (8)). Thus, the present proposal might have impact on fundamental cell biology mechanisms of polarity and development, or the discovery of novel substances improving plant development and health.
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