CAMEL in the canal: Regulation of PIN proteins during canalization (Science)

Auxin transport during development or wound regeneration is known to require auxin-induced channel or ‘canal’ formation that includes polar localization of PIN auxin transport proteins. Hajný and colleagues have characterized a receptor-like kinase (RLK) complex involved in auxin-induced pattern formation as well as PIN localization. The authors identified CAMEL, a membrane-localized RLK, and its interactor, CANAR, an auxin-responsive kinase, functioning downstream of the TIR1/AFB-WRKY23 transcriptional auxin signaling pathway. Knockout mutants of these proteins have disrupted auxin levels and abnormal leaf venation and wound regeneration responses, suggesting a direct role in auxin signaling or transport. Further biochemical and genetic investigations suggested CAMEL to be necessary for phosphorylation-dependent intracellular trafficking and localization of the PIN1 transporter. The authors propose CANAR to be a negative regulator of CAMEL. Thus, this study adds a novel component in the puzzle to solve auxin signaling and transport mechanisms. (Summary by Pavithran Narayanan @pavi_narayanan) Science 10.1126/science.aba3178