Peptide hormones are signals that determine the growth, development and defense in plants. RALF (Rapid Alkalinization Factor) is a peptide hormone ubiquitous in the plant kingdom and is involved in cell expansion. RALF peptides in Arabidopsis are organized in a 37 members multigene family, some of them are tissue-specific and others are expressed throughout the plant. Our main goal is to elucidate how RALF peptides function in plants and to determine its mechanism of action. This project is organized in two subprojects that, in common, have the same main goal. In the first, we are proposing the characterization of the AtRALF31, 33 and 34 isoforms, all of them mainly expressed in leaves. In order to do that we are going to obtain mutants, overexpressors and transgenics expressing the specific promoters fused to reporter genes. Preliminary results obtained in the first year of my master's degree showed that mutant plants for AtRALF33 have larger leaves, longer roots and longer hypocotyls, suggesting a role in cell expansion. In the second subproject we are going to use the affinity purification technique (TAP) to identify putative AtRALF1 interacting proteins a root-specific isoform. TAP technique enables the isolation of interacting proteins "in planta" and its application has been instrumental in the identification of new proteins involved in hormone response.
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