The nucleus is a dynamic organelle whose positioning and movement is highly coordinated throughout plant development and differs between cell types. Upon the initiation and subsequent elongation of root hairs, the nucleus moves from a central position to the tip of the growing root hair. Nakamura et al. investigated the mechanism behind this essential nuclear movement, focusing on the role of auxin and Rho-GTPase signaling to coordinate actin changes. The authors first noted that the nucleus moved from a central position in meristem cells to the inner epidermal plasma membrane during elongation and then to the outer domain into the emerging hair bulge. This nuclear movement was disrupted when auxin concentrations were altered and also when vacuolar development was impaired. By utilizing mutants in Rho-of-Plant (ROP) signaling, ROP activation was found to be important for inner polar nuclear positioning and, in combination with mutants impaired in auxin signaling, this ROP activation shown to act synergistically with auxin signaling. Most prominently, nuclei lose polar positioning and have decreased velocity when the actin cytoskeleton is disrupted. The study places multiple ROP and auxin signaling mediators in a pathway which further elucidates nuclei movement in root hair initiation and emergence as well as indicates a role for actin in this process. (Summary by Alecia Biel) Plant Physiol. 10.1104/pp.17.00713.
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