%0 Journal Article
%T Lipid kinases PIP5K7 and PIP5K9 are required for polyamine-triggered K+ efflux in Arabidopsis roots.
%A Zarza X
%A Van Wijk R
%A Shabala L
%A Hunkeler A
%A Lefebvre M
%A Rodriguez-Villalón A
%A Shabala S
%A Tiburcio AF
%A Heilmann I
%A Munnik T
%J Plant J
%V 104
%N 2
%D 10 2020
%M 32666545
%F 7.091
%R 10.1111/tpj.14932
%X Polyamines, such as putrescine, spermidine and spermine (Spm), are low-molecular-weight polycationic molecules present in all living organisms. Despite their implication in plant cellular processes, little is known about their molecular mode of action. Here, we demonstrate that polyamines trigger a rapid increase in the regulatory membrane lipid phosphatidylinositol 4,5-bisphosphate (PIP2 ), and that this increase is required for polyamine effects on K+ efflux in Arabidopsis roots. Using in vivo 32 Pi -labelling of Arabidopsis seedlings, low physiological (μm) concentrations of Spm were found to promote a rapid PIP2 increase in roots that was time- and dose-dependent. Confocal imaging of a genetically encoded PIP2 biosensor revealed that this increase was triggered at the plasma membrane. Differential 32 Pi -labelling suggested that the increase in PIP2 was generated through activation of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) activity rather than inhibition of a phospholipase C or PIP2 5-phosphatase activity. Systematic analysis of transfer DNA insertion mutants identified PIP5K7 and PIP5K9 as the main candidates involved in the Spm-induced PIP2 response. Using non-invasive microelectrode ion flux estimation, we discovered that the Spm-triggered K+ efflux response was strongly reduced in pip5k7 pip5k9 seedlings. Together, our results provide biochemical and genetic evidence for a physiological role of PIP2 in polyamine-mediated signalling controlling K+ flux in plants.