Abstract
How plant cells determine the direction of polar auxin transport is a central question in plant development. PIN auxin efflux transporters often show polar localization, and are considered to play a central role in determining auxin distribution patterns. However, signaling factors governing polar localization of PINs remain to be elucidated. We have previously shown that auxin promotes cell interdigitation in leaf epidermal pavement cells by activating Rho-like GTPase family from plants (ROP). The activation of the interdigitation by ROP requires PIN1-dependent polarized auxin export at the tip of lobes. We found that the polar localization of the auxin efflux carrier PIN1 protein is altered in rop mutants. Our results suggest that ROPs regulate endocytosis as well as recycling of PIN1, which participates in the establishment of PIN1 polarity. We propose that a positive feedback regulation of auxin activation of ROP, which involves polar PIN1 distribution, is critical for the interdigitation of pavement cells in Arabidopsis leaves.
