Unique cell wall abnormalities in the putative phosphoinositide phosphatase mutant AtSAC9

• Published in: Planta Vol. 234; no. 5; pp. 993 - 1005
• Main Authors: Vollmer, Almut H., Youssef, Nabil N., DeWald, Daryll B.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer 01.11.2011; Springer-Verlag; Springer Nature B.V
• Subjects: Agriculture; Alleles; Arabidopsis - cytology; Arabidopsis - growth & development; Arabidopsis Proteins - genetics; Biological and medical sciences; Biomedical and Life Sciences; Cell lines; Cell Membrane - metabolism; Cell membranes; Cell Wall - metabolism; Cell walls; Cytokinesis; Cytoskeleton - metabolism; Ecology; Epidermal cells; Forestry; Fundamental and applied biological sciences. Psychology; Life Sciences; Microscopy, Electron, Transmission; Original Article; Phenotype; Phosphatidylinositol Phosphates - genetics; Phosphatidylinositols; Phosphoric Monoester Hydrolases - genetics; Plant cells; Plant Cells - metabolism; Plant Cells - ultrastructure; Plant roots; Plant Roots - growth & development; Plant Roots - metabolism; Plant Roots - ultrastructure; Plant Sciences; Plants; Roots; Seedlings; SAC9; PtdIns(4,5)P; Localized cell wall formation; Root morphology; Ultrastructure; Phosphatidylinositol 4,5-bisphosphate; TEM; Cell wall; Phosphoinositide; Plant biology; Phosphoric monoester hydrolases; Esterases; Arabidopsis thaliana; Phosphatidylinositol; Cruciferae; Dicotyledones; Angiospermae; Root; Enzyme; Arabidopsis; Morphology; Hydrolases; Spermatophyta; Mutation; Experimental plant; Formation
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/s00425-011-1454-4

SAC9 is a putative phosphoinositide phosphatase in Arabidopsis thaliana involved in phosphoinositide signaling. sac9-1 plants have a constitutively stressed phenotype with shorter roots which notably accumulate phosphatidylinositol 4,5-bisphosphate and its hydrolysis product inositol trisphosphate. We investigated the primary roots of sac9-1 seedlings at the cytological and ultrastructural level to determine the structural basis for this altered growth. Despite the normal appearance of organelles and cytoplasmic elements, our studies reveal extreme abnormalities of cell wall and membrane structures in sac9-1 primary root cells, regardless of cell type, position within the meristematic area, and plane of section. Cell wall material was deposited locally and in a range of abnormal shapes, sometimes completely fragmenting the cell. Simple protuberances, broad flanges, diffuse patches, elaborate folds, irregular loops and other complex three-dimensional structures were found to extend randomly from the pre-existing cell wall. Abundant vesicles and excessive membrane material were associated with these irregular wall structures. We argue that a perturbed phosphoinositide metabolism most likely induces these observed abnormalities and hypothesize that a disorganized cytoskeleton and excessive membrane trafficking mediate the cell wall defects.