Biology subjects

Schwarzerova, K.

Publications and source records attributed to Schwarzerova, K..

3 recordsLinked to original sources

bioRxiv2025

Independent roles of Arp2/3 complex and RIC4 protein in the control of epidermal cell shape

The aim of this study was to determine whether RIC4, a CRIB domain-containing protein that functions as an effector of ROP GTPases, and the Arp2/3 complex, an actin nucleator, functionally cooperate in controlling the shape of Arabidopsis cotyledon epidermal cells. The combination of KO mutants demonstrated that loss of RIC4 and loss of the Arp2/3 complex result in completely opposite epidermal cell shape phenotypes. The double KO mutation is phenotypically similar to the Arp2/3 mutation, and the effect of RIC4 loss is completely eliminated. Analysis of overexpression revealed that excess RIC4 significantly suppresses the formation of pavement cell lobes. However, RIC4 does not require an active Arp2/3 complex for this effect. Our data further show that overexpression of RIC4 has a specific actin stabilization effect in cotyledon epidermal cells. However, we could not demonstrate that actin stabilization is directly related to the cell shape changes that RIC4 overexpression induces. In conclusion, RIC4 and the Arp2/3 complex do not share the same signaling pathway in their function in the control of cotyledon epidermal cell shape.

plant biology↗

bioRxiv2025

Nanodomain distribution and function of PIN-FORMED auxin efflux carriers in the plasma membrane of tobacco cells are defined by their interactions with the cell wall

Plant development is under the morphogenic control of auxin. In addition to biosynthesis and metabolism, auxin concentration gradients are maintained by directional intercellular transport via PIN-FORMED (PIN) auxin efflux carriers. Although the structure-function properties of PINs have been described, it is still unclear whether individual members of PIN family could localize differently within the plasma membrane (PM) and whether their nanodomain distribution defines their function. To address this, we used cultured tobacco cells (Nicotiana tabacum L., cv. BY-2) and revealed by RNA-seq and RT-qPCR the cell stage-specific presence of transcripts of tobacco PIN homologs. We used high-resolution light microscopy and two independent immunoelectron microscopy techniques in cell lines expressing functional GFP-tagged inducible versions of NtPIN11T, NtPIN2T and NtPIN3bT. We show that NtPINs are distributed within specific PM nanodomains and that removal of the cell wall alters their appearance. By a series of in vivo microscopic observations, we provide evidence that NtPIN11T is the most homogenously distributed and the least mobile NtPIN. Pharmacological treatments suggested that the immobilization of NtPIN11T depends on the actin and microtubular cytoskeleton and the cell wall composition. Using comparative co-immunoprecipitation (co-IP) analysis of isolated membrane fractions for all three NtPINs we finally identified several novel interaction partners indicating a preferential association of NtPIN11T with cell wall GPI-anchored arabinogalactan proteins. In conclusion, our results suggest a model in which specific immobilization of PINs through interactions with the cell wall affects their function.

plant biology↗

bioRxiv2022

ARP2/3 complex associates with peroxisomes to participate in pexophagy in plants

ARP2/3 is a heteroheptameric protein complex evolutionary conserved in all eukaryotic organisms. Its conserved role is based on the induction of actin polymerization at the interface between membranes and the cytoplasm. Plant ARP2/3 has been reported to participate in actin reorganization at the plasma membrane during polarized growth of trichomes and at the plasma membrane-endoplasmic reticulum contact sites. We demonstrate here that individual plant subunits of ARP2/3 fused to fluorescent proteins form motile dot-like structures in the cytoplasm that are associated with plant peroxisomes. ARP2/3 dot structure is found at the peroxisome periphery and contains assembled ARP2/3 complex and WAVE/SCAR complex subunit NAP1. This dot occasionally colocalizes with the autophagosome, and under conditions that affect the autophagy, colocalization between ARP2/3 and the autophagosome increases. ARP2/3 subunits co-immunoprecipitate with ATG8f marker. Since mutants lacking functional ARP2/3 complex have more peroxisomes than WT, we link the ARP2/3 complex on peroxisomes to the process of peroxisome degradation by autophagy called pexophagy. Additionally, several other peroxisomal proteins colocalize with ARP2/3 dot on plant peroxisomes. Our results suggest a specific role of ARP2/3 and actin in the peroxisome periphery, presumably in membrane remodelling. We hypothesize that this role of ARP2/3 aids processes at the peroxisome periphery such as peroxisome degradation through autophagy or regulation of peroxisomal proteins localization or function. Significance statementARP2/3 complex-positive dots associate exclusively with peroxisomes in plant cells, where it colocalizes with autophagosome marker ATG8f and several other proteins. Our experiments link ARP2/3 to pexophagy: colocalization between ARP2/3 dots and autophagosome increases when autophagy processes are induced or inhibited; ARP2/3 and ATG8f colocalize and co-immunoprecipitate, and finally, ARP2/3 mutants cells contain more peroxisomes than WT. Our results suggest a novel role of ARP2/3 in peroxisome structure and function regulation.

cell biology↗