title: Loss-of-function and gain-of-function mutations in FAB1A/B impair endomembrane homeostasis, conferring pleiotropic developmental abnormalities in Arabidopsis.
abstract: In eukaryotic cells, PtdIns 3,5-kinase, Fab1/PIKfyve produces PtdIns (3,5) P(2) from PtdIns 3-P, and functions in vacuole/lysosome homeostasis. Herein, we show that expression of Arabidopsis (Arabidopsis thaliana) FAB1A/B in fission yeast (Schizosaccharomyces pombe) fab1 knockout cells fully complements the vacuole morphology phenotype. Subcellular localizations of FAB1A and FAB1B fused with green fluorescent protein revealed that FAB1A/B-green fluorescent proteins localize to the endosomes in root epidermal cells of Arabidopsis. Furthermore, reduction in the expression levels of FAB1A/B by RNA interference impairs vacuolar acidification and endocytosis. These results indicate that Arabidopsis FAB1A/B functions as PtdIns 3,5-kinase in plants and in fission yeast. Conditional knockdown mutant shows various phenotypes including root growth inhibition, hyposensitivity to exogenous auxin, and disturbance of root gravitropism. These phenotypes are observed also in the overproducing mutants of FAB1A and FAB1B. The overproducing mutants reveal additional morphological phenotypes including dwarfism, male-gametophyte sterility, and abnormal floral organs. Taken together, this evidence indicates that imbalanced expression of FAB1A/B impairs endomembrane homeostasis including endocytosis, vacuole formation, and vacuolar acidification, which causes pleiotropic developmental phenotypes mostly related to the auxin signaling in Arabidopsis.
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto 606-8501, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Hirano
authors.forename: Tomohiko
authors.initials: T
authors.lastname: Matsuzawa
authors.forename: Kaoru
authors.initials: K
authors.lastname: Takegawa
authors.forename: Masa H
authors.initials: MH
authors.lastname: Sato
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000201:enzymology / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics*; D002462:Cell Membrane / Q000502:physiology*; D011992:Endosomes / Q000502:physiology*; D055785:Gene Knockdown Techniques; D005816:Genetic Complementation Test; D018522:Gravitropism; D006706:Homeostasis; D007210:Indoleacetic Acids / Q000494:pharmacology; D009154:Mutation; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics*; D051479:Plant Infertility; D018517:Plant Roots / Q000254:growth & development; D030821:Plants, Genetically Modified / Q000166:cytology / Q000201:enzymology / Q000235:genetics; D018749:RNA, Plant / Q000235:genetics; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D018749:RNA, Plant; C547216:FAB1A protein, Arabidopsis; C547217:FAB1B protein, Arabidopsis; D017853:Phosphotransferases (Alcohol Group Acceptor)