Identification and Dynamics of Arabidopsis Adaptor Protein-2 Complex and Its Involvement in Floral Organ Development

Abstract

ORCID ID: 0000-0003-4154-9967 (S.Y.).The adaptor protein-2 (AP-2) complex is a heterotetramer involved in clathrin-mediated endocytosis of cargo proteins from the plasma membrane in animal cells. The homologous genes of AP-2 subunits are present in the genomes of plants; however, their identities and roles in endocytic pathways are not clearly defined in plants. Here, we reveal the molecular composition of the AP-2 complex of Arabidopsis thaliana and its dynamics on the plasma membrane. We identified all of the a-, b-, s-, and m-subunits of the AP-2 complex and detected a weak interaction of the AP-2 complex with clathrin heavy chain. The m-subunit protein fused to green fluorescent protein (AP2M-GFP) was localized to the plasma membrane and to the cytoplasm. Live-cell imaging using a variable-angle epifluorescence microscope revealed that AP2M-GFP transiently forms punctate structures on the plasma membrane. Homozygous ap2m mutant plants exhibited abnormal floral structures, including reduced stamen elongation and delayed anther dehiscence, which led to a failure of pollination and a subsequent reduction of fertility. Our study provides a molecular basis for understanding AP-2-dependent endocytic pathways in plants and their roles in floral organ development and plant reproduction.

Helping Hands for Budding Prospects: ENTH/ANTH/VHS Accessory Proteins in Endocytosis, Vacuolar Transport, and Secretion

“…Various mutants in AP-2 subunits show impaired CME and developmental aberrations that presumably are the consequence of these cellular defects. These results, plus the dynamic spatiotemporal localization of AP-2 components at the PM, support the notion that AP-2 is an early adaptor complex for clathrin recruitment/assembly (Di Rubbo et al, 2013;Fan et al, 2013;Kim et al, 2013;Yamaoka et al, 2013) in plant endocytosis.…”

Involvement of Adapter Protein Complex 4 in Hypersensitive Cell Death Induced by Avirulent Bacteria

“…This is consistent with our previous report that the AP-2 subunit AP2M is required for both RPM1-mediated ETI and RPS2-mediated ETI, but not for RPS4-mediated ETI (Hatsugai et al, 2016). AP2M plays a central role in clathrin-mediated endocytotic pathway from the plasma membrane to the vacuole (Di Rubbo et al, 2013;Fan et al, 2013;Kim et al, 2013;Yamaoka et al, 2013). These results suggest that the ETI-related immunesignaling components undergo endocytic internalization.…”

Cellulose Synthesis and Its Regulation

“…In CME, the adaptor protein complex 2 (AP2) acts in recruiting plasma membrane protein cargo and clathrin triskelia of the clathrin coat to the sites of endocytic vesicle formation (Chen et al, 2011). μ2 (At5g46630), also referred to as AP2M, is a subunit of the AP2 complex in Arabidopsis (L. Segal, 1959;Li et al, 2012a;Bashline et al, 2013;Yamaoka et al, 2013). Live cell imaging analysis confirmed that the dynamics of μ2 is associated with CME in Arabidopsis (Bashline et al, 2013).…”