Directional intercellular transport of the phytohormone auxin mediated by PIN-FORMED (PIN) efflux carriers has essential roles in both coordinating patterning processes and integrating multiple external cues by rapidly redirecting auxin fluxes. PIN activity is therefore regulated by multiple internal and external cues, for which the underlying molecular mechanisms are not fully elucidated. Here, we demonstrate that 3'-PHOSPHOINOSITIDE-DEPENDENT PROTEIN KINASE1 (PDK1), which is conserved in plants and mammals, functions as a molecular hub that perceives upstream lipid signalling and modulates downstream substrate activity through phosphorylation. Using genetic analysis, we show that the loss-of-function Arabidopsis pdk1.1 pdk1.2 mutant exhibits a plethora of abnormalities in organogenesis and growth due to defective polar auxin transport. Further cellular and biochemical analyses reveal that PDK1 phosphorylates D6 protein kinase, a well-known upstream activator of PIN proteins. We uncover a lipid-dependent phosphorylation cascade that connects membrane-composition-based cellular signalling with plant growth and patterning by regulating morphogenetic auxin fluxes.

Department of Applied Genetics and Cell Biology University of Natural Resources and Life Sciences Vienna Austria

Institute of Experimental Botany The Czech Academy of Sciences Prague Czech Republic

Institute of Science and Technology Austria Klosterneuburg Austria

Joint Center for Single Cell Biology School of Agriculture and Biology Shanghai Jiao Tong University Shanghai China

National Key Laboratory of Plant Molecular Genetics CAS Centre for Excellence in Molecular Plant Sciences Shanghai Institute of Plant Physiology and Ecology Chinese Academy of Sciences Shanghai China

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Nat Plants. 2020 Jul;6(7):897. doi: 10.1038/s41477-020-0719-y. PubMed

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