title: Myrosin cell development is regulated by endocytosis machinery and PIN1 polarity in leaf primordia of Arabidopsis thaliana.
abstract: Myrosin cells, which accumulate myrosinase to produce toxic compounds when they are ruptured by herbivores, form specifically along leaf veins in Arabidopsis thaliana. However, the mechanism underlying this pattern formation is unknown. Here, we show that myrosin cell development requires the endocytosis-mediated polar localization of the auxin-efflux carrier PIN1 in leaf primordia. Defects in the endocytic/vacuolar SNAREs (syp22 and syp22 vti11) enhanced myrosin cell development. The syp22 phenotype was rescued by expressing SYP22 under the control of the PIN1 promoter. Additionally, myrosin cell development was enhanced either by lacking the activator of endocytic/vacuolar RAB5 GTPase (VPS9A) or by PIN1 promoter-driven expression of a dominant-negative form of RAB5 GTPase (ARA7). By contrast, myrosin cell development was not affected by deficiencies of vacuolar trafficking factors, including the vacuolar sorting receptor VSR1 and the retromer components VPS29 and VPS35, suggesting that endocytic pathway rather than vacuolar trafficking pathway is important for myrosin cell development. The phosphomimic PIN1 variant (PIN1-Asp), which is unable to be polarized, caused myrosin cells to form not only along leaf vein but also in the intervein leaf area. We propose that Brassicales plants might arrange myrosin cells near vascular cells in order to protect the flux of nutrients and water via polar PIN1 localization.
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirakawa
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Haruko
authors.initials: H
authors.lastname: Ueda
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Graduate School of Biostudies, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kohchi
authors.affiliation: Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan ihnishi@gr.bot.kyoto-u.ac.jp.
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D016764:Cell Polarity; D004705:Endocytosis; D018506:Gene Expression Regulation, Plant; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D018515:Plant Leaves / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D058526:Plant Vascular Bundle / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D021381:Protein Transport
chemical_list: D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; C116363:PIN1 protein, Arabidopsis