Structure-function analysis of the auxin transport regulatory D6 PROTEIN KINASE in Arabidopsis thaliana

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The hormone auxin controls many decisions in plant development as well as all tropic responses. The correct distribution of auxin within the plant is achieved by a system of import and export carriers. D6 PROTEIN KINASE (D6PK) is important for the activation of PIN-FORMED (PIN) auxin exporters and mutants of D6PK have defects in lateral root formation, shoot differentiation, and various tropic growth responses. D6PK as PINs are polarly distributed in plant cells and thereby direct auxin transport streams in the plant. Understanding the trafficking mechanisms underlying D6PK and PIN transport is therefore pivotal to understand plant development and tropisms. Here, we aim at understanding the molecular mechanisms that target D6PK to the plasma membrane and that regulate D6PK plasma membrane association and kinase activity. We showed that D6PK associates with phospholipids in the plasma membrane through a positively charged lysine-motif and now will address the role of repeats containing cysteines for membrane binding and kinase activity. To place these structure-function analysis in a broader context, we also aim at determining the crystal structure of D6PK and to examine the behaviour of D6PK in planta in selected genetic backgrounds.