Review: Outer, inner and planar polarity in the Arabidopsis root

Despite vast differences across all living organisms, most eukaryotes display some form of cellular polarity which enables them to carry out specialized functions. The coordination of cell polarity within a single tissue layer is known as planar polarity. Nakamura and Grebe highlight the unique execution of planar polarity in Arabidopsis root cells. Setting the stage for root hair development, Rho-of-plants (ROP) proteins accumulate near the basal ends of root cells at the outer plasma membrane. This site-specific ROP accumulation is dependent on proper sterol composition and cytoskeleton function and organization. Furthermore, outer polar domains of root epidermal cells appear enriched in proteins involved in the defense and response of biotic and abiotic stresses. This polar distribution has been found to rely on the trans-Golgi network, endocytic trafficking, and actin function for correct protein targeting. Elucidating these mechanisms will not only help further our understanding of fundamental plant development but also how plants sense and respond to environmental stress. (Summary by Alecia Biel) Curr. Opin. Plant Biol. 10.1016/j.pbi.2017.08.002

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