Lipid kinases PIP5K7 and PIP5K9 are required for polyamine‐triggered K⁺ efflux in Arabidopsis roots

Abstract

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 (PIP 2), and that this increase is required for polyamine effects on K + efflux in Arabidopsis roots. Using in vivo 32 P i-labelling of Arabidopsis seedlings, low physiological (lM) concentrations of Spm were found to promote a rapid PIP 2 increase in roots that was time-and dose-dependent. Confocal imaging of a genetically encoded PIP 2 biosensor revealed that this increase was triggered at the plasma membrane. Differential 32 P i-labelling suggested that the increase in PIP 2 was generated through activation of phosphatidylinositol 4-phosphate 5-kinase (PIP5K) activity rather than inhibition of a phospholipase C or PIP 2 5-phosphatase activity. Systematic analysis of transfer DNA insertion mutants identified PIP5K7 and PIP5K9 as the main candidates involved in the Spm-induced PIP 2 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 PIP 2 in polyamine-mediated signalling controlling K + flux in plants.

Arabidopsis phosphatidylinositol 4‐phosphate 5‐kinase genes PIP5K7, PIP5K8, and PIP5K9 are redundantly involved in root growth adaptation to osmotic stress

“…In our GUS reporter analysis, upstream intergenic regions of PIP5K7 and PIP5K9 exhibited promoter activity preferentially in meristematic and vascular tissues of shoots, roots, and inflorescences. This pattern is basically consistent with those reported previously (Bauby et al , 2007; Lou et al , 2007; Zarza et al , 2020). Although an upstream region of PIP5K9 did not show promoter activity in the root meristem in a former study (Lou et al , 2007), this discrepancy may stem from variations in the 1.1‐ and 3.5‐kb upstream regions from the PIP5K9 initiation codon examined in the former and our study, respectively.…”

“…As for the PIP5K7–9 subgroup genes, PIP5K9 overexpression lines have been shown to exhibit a short root phenotype due to repression of the cytosolic invertase CINV1 through the physical interaction between PIP5K9 and CINV1 (Lou et al , 2007). Recently, it was reported that PIP5K7 and PIP5K9 are responsible for the polyamine‐triggered increase in root PtdIns(4,5) P 2 levels and subsequent K + ‐efflux activation, and that main root growth of the pip5k7pip5k9 double mutant was hypersensitive to polyamine and KCl treatments (Zarza et al , 2020). These findings suggest involvement of the PIP5K7–9 subgroup genes in controlling root growth under stress conditions.…”

Spermine and Spermidine Priming against Botrytis cinerea Modulates ROS Dynamics and Metabolism in Arabidopsis

“…The hunt is open to uncover possible PA sensors in plants, encouraged by their existence in bacteria and by the observations in this work. Perhaps extracellular PA sensing is intrinsically linked to lipid signalling now recognized as a crucial component of PA signalling events [ 84 ].…”

Modulation of Ion Transport Across Plant Membranes by Polyamines: Understanding Specific Modes of Action Under Stress

“…PAs block animal inward rectifier Kir2.1 but also activate it by strengthening the interaction with PIP 2 ( Xie et al, 2005 ). PAs induced a rapid increase in PIP 2 in Arabidopsis seedling, triggering a massive K + efflux mediated by outward-rectifying GORK channels ( Zarza et al, 2020 ). This mechanism appears to be specific for Arabidopsis.…”