Molecular determinants specifying cellular polarity of ENHANCER OF PINOID

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Mutation of the Arabidopsis thaliana gene ENHANCER OF PINOID (ENP) in pinoid mutant background leads to complete reversal of the polarity of the auxin transporter PINI in the epidermis. The disturbed auxin transport leads to embryos lacking cotyledons. In adult stages, plants with blind-ending stems lacking flowers develop. Our work has revealed that ENP, a homolog of the phototropic factor NPH3, is precisely co-localized with PINI. However, ENP, a protein with characteristics of soluble proteins, reaches its destination on a different way than PINI, a transmembrane protein. Our preliminary work shows, that the BTB/POZ domain of ENP is required for its polar localization whereas the C-terminal regions likely harbour functionality for PINI polarity and/or auxin transport. ENP is obviously a crucial factor required for epidermal cell polarity. However, the molecular mechanisms, which mediate its own polarity remain elusive. A major key to understand ENP polarity and function lies in its interactions with other cellular elements. Therefore, this application proposes a series of experiments, which investigate the cellular dynamics of ENP, the significance of its domains as well as the analysis of interactors by advanced means.