RT Journal Article SR Electronic T1 A lipid code-dependent phosphoswitch directs PIN-mediated auxin efflux in Arabidopsis development JF bioRxiv FD Cold Spring Harbor Laboratory SP 755504 DO 10.1101/755504 A1 Shutang Tan A1 Xixi Zhang A1 Wei Kong A1 Xiao-Li Yang A1 Gergely Molnár A1 Jiří Friml A1 Hong-Wei Xue YR 2019 UL http://biorxiv.org/content/early/2019/09/03/755504.abstract AB Directional intercellular transport of the phytohormone auxin mediated by PIN FORMED (PIN) efflux carriers plays essential roles in both coordinating patterning processes and integrating multiple external cues by rapidly redirecting auxin fluxes. Multilevel regulations of PIN activity under internal and external cues are complicated; however, the underlying molecular mechanism remains elusive. Here we demonstrate that 3’-Phosphoinositide-Dependent Protein Kinase1 (PDK1), which is conserved in plants and mammals, functions as a molecular hub integrating the upstream lipid signalling and the downstream substrate activity through phosphorylation. Genetic analysis uncovers that loss-of-function Arabidopsis mutant pdk1.1 pdk1.2 exhibits a plethora of abnormalities in organogenesis and growth, due to the defective PIN-dependent auxin transport. Further cellular and biochemical analyses reveal that PDK1 phosphorylates D6 Protein Kinase to facilitate its activity towards PIN proteins. Our studies establish a lipid-dependent phosphorylation cascade connecting membrane composition-based cellular signalling with plant growth and patterning by regulating morphogenetic auxin fluxes.