title: Arabidopsis Qa-SNARE SYP2 proteins localized to different subcellular regions function redundantly in vacuolar protein sorting and plant development.
abstract: SYP2 proteins are a sub-family of Qa-SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors) that may be responsible for protein trafficking between pre-vacuolar compartments (PVC) and vacuoles. Arabidopsis thaliana SYP22/VAM3/SGR3 and SYP21/PEP12 proteins function independently, but are both reported to be essential for male gametophytic viability. Here, we systematically examined the redundancy of three SYP2 paralogs (i.e. SYP21, 22 and 23) using a Col-0 ecotype harboring a SYP2 paralog (SYP23/PLP) that lacked a transmembrane domain. Surprisingly, no visible phenotypes were observed, even in the double knockout syp21/pep12 syp23/plp. Deficiency of either SYP21/PEP12 or SYP23/PLP in the syp22 background resulted in a defect in vacuolar protein sorting, characterized by abnormal accumulation of protein precursors in seeds. SYP21/PEP12 knockdown enhanced the syp22 phenotype (i.e. semi-dwarfism, poor leaf vein development and abnormal development of myrosin cells), and additional knockout of SYP23/PLP further aggravated the phenotype. A GFP-SYP23/PLP fusion localized to the cytosol, but not to the PVC or vacuolar membrane, where SYP21/PEP12 or SYP22/VAM3, respectively, were localized. Immunoprecipitation analysis showed that SYP23/PLP interacted with the vacuolar Qb- and Qc-SNAREs, VTI11 and SYP5, respectively, suggesting that SYP23/PLP is able to form a SNARE complex anchoring the membrane. Unexpectedly, we found that expression of multiple copies of a genomic fragment of SYP23/PLP suppressed the abnormal syp22-3 phenotype. Thus, SYP2 proteins, including cytosolic SYP23/PLP, appear to function redundantly in vacuolar trafficking and plant development.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirakawa
authors.forename: Haruko
authors.initials: H
authors.lastname: Ueda
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Koumoto
authors.forename: Takashi L
authors.initials: TL
authors.lastname: Shimada
authors.forename: Maki
authors.initials: M
authors.lastname: Kondo
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
authors.forename: Yudai
authors.initials: Y
authors.lastname: Okuyama
authors.forename: Mikio
authors.initials: M
authors.lastname: Nishimura
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation; D055786:Gene Knockout Techniques; D009154:Mutation; D010641:Phenotype; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: C489890:ATPEP12 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050765:Qa-SNARE Proteins; C108430:Vam3 protein, Arabidopsis