PIN polarity control by Arabidopsis WAV3-type proteins

Wider research context: Polarity acquisition in cellular and organismal context defines differentiation processes in organisms. Higher plants are no exception, with numerous processes driving polar protein deposition to adjust intercellular communication and adaptation to the plants' environment. Canonical PIN-FORMED (PIN) transport proteins are among the most intensely studied polarly localized proteins in plants, exhibiting variable accumulation at different plasma membrane domains, thereby shaping directional cellular efflux of the plant growth regulator auxin. Control of polar PIN localization is central to polarity acquisition and differentiation processes, and our recent work identified the small WAV3 Arabidopsis family of E3 ubiquitin ligases as determinants of apical-basal cellular PIN deposition. Specifically, combinatorial loss of WAV3/WAVH genes causes basal localization of otherwise apically localized PINs. However, mechanisms of WAV3/WAVH-PIN crosstalk are unknown. Objectives: We intend to characterize molecular principles by which WAV3 and closely related proteins control PIN polarity acquisition. Based on our preliminary work, we aim to position WAV3 proteins in regulatory networks of protein sorting and auxin signaling and will test a hypothetical function of WAV3 as positional determinant in polarity establishment.