title: HAPLESS13, the Arabidopsis μ1 adaptin, is essential for protein sorting at the trans-Golgi network/early endosome.
abstract: In plant cells, secretory and endocytic routes intersect at the trans-Golgi network (TGN)/early endosome (EE), where cargos are further sorted correctly and in a timely manner. Cargo sorting is essential for plant survival and therefore necessitates complex molecular machinery. Adaptor proteins (APs) play key roles in this process by recruiting coat proteins and selecting cargos for different vesicle carriers. The µ1 subunit of AP-1 in Arabidopsis (Arabidopsis thaliana) was recently identified at the TGN/EE and shown to be essential for cytokinesis. However, little was known about other cellular activities affected by mutations in AP-1 or the developmental consequences of such mutations. We report here that HAPLESS13 (HAP13), the Arabidopsis µ1 adaptin, is essential for protein sorting at the TGN/EE. Functional loss of HAP13 displayed pleiotropic developmental defects, some of which were suggestive of disrupted auxin signaling. Consistent with this, the asymmetric localization of PIN-FORMED2 (PIN2), an auxin transporter, was compromised in the mutant. In addition, cell morphogenesis was disrupted. We further demonstrate that HAP13 is critical for brefeldin A-sensitive but wortmannin-insensitive post-Golgi trafficking. Our results show that HAP13 is a key link in the sophisticated trafficking network in plant cells.
authors.affiliation: State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
authors.forename: Jia-Gang
authors.initials: JG
authors.lastname: Wang
authors.forename: Sha
authors.initials: S
authors.lastname: Li
authors.forename: Xin-Ying
authors.initials: XY
authors.lastname: Zhao
authors.forename: Liang-Zi
authors.initials: LZ
authors.lastname: Zhou
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Huang
authors.forename: Chong
authors.initials: C
authors.lastname: Feng
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D033961:Adaptor Protein Complex 1 / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020126:Brefeldin A / Q000494:pharmacology; D011992:Endosomes / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D007210:Indoleacetic Acids / Q000378:metabolism; D009154:Mutation; D030821:Plants, Genetically Modified; D021381:Protein Transport; D015398:Signal Transduction / Q000235:genetics; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: C583122:AP1M2 protein, Arabidopsis; D033961:Adaptor Protein Complex 1; D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D020126:Brefeldin A