Sphingolipids mediate polar sorting of PIN2 through phosphoinositide consumption at the trans-Golgi network.

The lipid composition of organelles acts as a landmark to define membrane identity and specify subcellular function. Phosphoinositides are anionic lipids acting in protein sorting and trafficking at the trans-Golgi network (TGN). In animal cells, sphingolipids control the turnover of phosphoinositides through lipid exchange mechanisms at endoplasmic reticulum/TGN contact sites.

A PAMP-triggered MAPK cascade inhibits phosphatidylinositol 4,5-bisphosphate production by PIP5K6 in Arabidopsis thaliana.

The phosphoinositide kinase PIP5K6 has recently been identified as a target for the mitogen-activated protein kinase (MAPK) MPK6. Phosphorylation of PIP5K6 inhibited the production of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P ), impacting membrane trafficking and cell expansion in pollen tubes. Here, we analyzed whether MPK6 regulated PIP5K6 in vegetative Arabidopsis cells in response to the pathogen-associated molecular pattern (PAMP) flg22.

MAPKs Influence Pollen Tube Growth by Controlling the Formation of Phosphatidylinositol 4,5-Bisphosphate in an Apical Plasma Membrane Domain.

An apical plasma membrane domain enriched in the regulatory phospholipid phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P] is critical for polar tip growth of pollen tubes. How the biosynthesis of PtdIns(4,5)P by phosphatidylinositol 4-phosphate 5-kinases (PI4P 5-kinases) is controlled by upstream signaling is currently unknown. The pollen-expressed PI4P 5-kinase PIP5K6 is required for clathrin-mediated endocytosis and polar tip growth in pollen tubes.

Arabidopsis phosphatidylinositol 4-phosphate 5-kinase 2 contains a functional nuclear localization sequence and interacts with alpha-importins.

The Arabidopsis phosphoinositide kinase PIP5K2 has been implicated in the control of membrane trafficking and is important for development and growth. In addition to cytosolic functions of phosphoinositides, a nuclear phosphoinositide system has been proposed, but evidence for nuclear phosphoinositides in plants is limited. Fluorescence-tagged variants of PIP5K2 reside in the nucleus of Arabidopsis root meristem cells, in addition to reported plasma membrane localization.

Guilt by Association: A Phenotype-Based View of the Plant Phosphoinositide Network.

Eukaryotic membranes contain small amounts of phospholipids that have regulatory effects on the physiological functions of cells, tissues, and organs. Phosphoinositides (PIs)-the phosphorylated derivatives of phosphatidylinositol-are one example of such regulatory lipids. Although PIs were described in plants decades ago, their contribution to the regulation of physiological processes in plants is not well understood.