Accumulation of phosphoinositides in distinct regions of the periarbuscular membrane

• Published in: The New phytologist 2019-03, Vol.221 (4), p.2213-2227
• Main Authors: Ivanov, Sergey, Harrison, Maria J.
• Format: Article
• Language: English
• Subjects: Anions; arbuscular mycorrhizal (AM) symbiosis; Arbuscular mycorrhizas; biotrophic interfacial complex (BIC); Cell Membrane - metabolism; Cells; Cortex; Diglycerides; Distribution; Endocytosis; Exocytosis; Fluorescence; Fluorescent Dyes - metabolism; fungus; Golgi apparatus; Lipids; Medicago truncatula - microbiology; Membranes; Microscopy, Fluorescence, Multiphoton; Morphology; Mutation - genetics; Mycorrhizae - metabolism; Phosphatidic acid; Phosphatidylinositols - metabolism; Phosphoinositides; Proteins; Regions; root; Spatial distribution; Symbiosis
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.15553

• Phosphoinositides and phosphatidic acid are small anionic lipids that comprise a minor proportion of total membrane lipids in eukaryotic cells but influence a broad range of cellular processes including endomembrane trafficking, signaling, exocytosis and endocytosis. • To investigate the spatial distribution of phosphoinositides during arbuscular mycorrhizal symbiosis, we generated fluorescent reporters of PI(4,5)P₂ and PI4P, as well as phosphatidic acid and diacylglycerol and used them to monitor lipid distribution on the cytoplasmic side of membrane bilayers in colonized cortical cells. • The PI4P reporter accumulated strongly on the periarbuscular membrane (PAM) and transiently labeled Golgi bodies, while the PA reporter showed differential labeling of endomembranes and the PAM. Surprisingly, the PI(4,5)P₂ reporter accumulated in small, discrete regions of the PAM on the arbuscule trunks, frequently in two regions on opposing sides of the hypha. A mutant reporter with reduced PI(4,5)P₂ binding capacity did not show these accumulations. • The PI(4,5)P₂-rich regions were detected at all phases of arbuscule development following branching, co-localized with membrane marker proteins potentially indicating high membrane bilayer content, and were associated with an alteration in morphology of the hypha. A possible analogy to the biotrophic interfacial membrane complex formed in rice infected with Magnaporthe orzyae is discussed.