Biology subjects

Malinska, K.

Publications and source records attributed to Malinska, K..

5 recordsLinked to original sources

bioRxiv2026

A Cajal body assembly factor regulates cell fate transitions in Arabidopsis

Ribonucleoprotein (RNP) condensates are emerging as key regulators of cell fate transitions, yet their functions have been largely linked to mRNA storage and translational control. Here, we uncover a role for Cajal body (CB)-mediated pre-mRNA splicing in coordinating the transition from stem cell divisions to differentiation in plants. We identify THREE-DIVISION MUTANT 3 (TDM3) as a cell cycle-regulated factor required for post-mitotic CB assembly. Loss of TDM3 or the CB scaffold protein COILIN delays differentiation and prolongs formative cell divisions. Transcriptome analysis revealed that TDM3 and COILIN jointly regulate pre-mRNA splicing, including transcripts controlling cell cycle and fate transitions. These findings establish CB-mediated splicing as a mechanism linking cell cycle progression to cellular differentiation.

cell 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↗

bioRxiv2020

A role of DAO1 in oxidation of IAA amino acid conjugates revealed through metabolite, high throughput transcript and protein level analysis.

Auxin metabolism is, together with auxin transport, a key determinant of auxin signalling output in plant cells, yet details on the underlying mechanisms and factors involved are still largely unknown. Processes involved in the auxin metabolism are subject to regulation based on numerous signals, including auxin concentration itself. Altered auxin availability and the subsequent changes of auxin metabolite profiles can therefore elucidate the function and regulatory role of individual elements in the auxin metabolic machinery. After analysing auxin metabolism in auxin dependent tobacco BY-2 cell line grown in presence or absence of synthetic auxin 2,4-D we found that both conditions were similarly characterized by very low levels of endogenous indole-3-acetic acid (IAA) and its metabolites. However, metabolic profiling after exogenous application of IAA uncovered that the concentration of N-(2-oxindole-3-acetyl)-L-aspartic acid (oxIAA-Asp), the most abundantly formed auxin metabolite in the control culture, dramatically decreased in auxin-starved conditions. To describe the molecular mechanism behind this regulation, we analysed transcriptome and proteome changes caused by auxin starvation. While no changes in the expression of auxin biosynthetic machinery were observed, many genes related to auxin conjugation and degradation showed differential expression. Selected putative auxin glycosylating enzymes as well as members of the Gretchen Hagen 3 gene family involved in auxin amino acid conjugation showed both up- and down-regulation. Contrarily to that, all tobacco homologs of Arabidopsis thaliana DIOXYGENASE FOR AUXIN OXIDATION 1 (DAO1), known to be responsible for the formation of oxIAA from IAA, showed significant downregulation at both transcript and protein levels. To validate the role of DAO1 in auxin metabolism, we performed auxin metabolite profiling in BY-2 mutants carrying either siRNA-silenced or CRISPR-Cas9-mutated NtDAO1, as well as in dao1-1 Arabidopsis thaliana plants. Both mutants showed not only expectedly lower levels of oxIAA, but also significantly lower abundance of oxidated amino acid conjugates of IAA (oxIAA-Asp). Our results thus represent the first direct evidence on DAO1 activity on IAA amino acid conjugates. Statement of significanceHere we present an analysis of auxin metabolism on metabolite, transcript and protein levels in tobacco BY-2 cell line, collectively identifying oxidation of IAA amino acid conjugates as a new role of DIOXYGENASE FOR AUXIN OXIDATION 1 within an auxin-level-responsive metabolic system.

plant biology↗

bioRxiv2018

Can Actin Depolymerization Actually Result In Increased Plant Resistance To Pathogens?

Introductory paragraphThe integrity of the actin cytoskeleton is essential for plant immune signalling1. Consequently, it is generally assumed that actin disruption reduces plant resistance to pathogen attack2-4. However, in a previous study, it was shown that actin depolymerisation triggers the salicylic acid (SA) signalling pathway5, which is interesting because increased SA is associated with enhanced plant resistance to pathogen attack6,7. Here, we attempt to resolve this seeming inconsistency by showing that the relationship between actin depolymerization and plant resistance is more complex than currently thought. We investigate the precise nature of this relationship using two completely different plant pathosystems: i) a model plant (Arabidopsis thaliana) and a bacterial pathogen (Pseudomonas syringae), and ii) an important crop (Brassica napus) and a fungal pathogen (Leptosphaeria maculans). We demonstrate that actin depolymerization induces a dramatic increase in SA levels and that the increased SA is biosynthesized by the isochorismate synthase pathway. In both pathosystems, this phenomenon leads to increased plant resistance.

plant biology↗