Biology subjects

Cvrckova, F.

Publications and source records attributed to Cvrckova, F..

7 recordsLinked to original sources

bioRxiv2026

Endogenous and environmentally modulated leaf shape plasticity in Boquila trifoliolata: how good is the evidence for mimicry?

Reports that the South American climbing vine Boquila trifoliolata modifies its leaf shape to mimic leaves of its host plant have raised considerable attention. Boquila leaf development was proposed to reflect visual inputs perceived in an unknown manner. However, the very existence of Boquila leaf shape mimicry remains inconclusive, since the reported observations are open to alternative explanations. We performed an initial quantitative characterization of leaf shape variability in glasshouse-cultured clonal Boquila plants grown without close host contact, and attempted to reproduce the leaf shape mimicry phenomenon under controlled culture conditions using live olive (Olea europaea) plants, artificial (decoy) olive or artificial ivy plants as supports. While we found leaves of variable shape (including those resembling ivy leaves) both in plants grown without host contact and in those climbing on live or decoy hosts, we did not observe any link between leaf shape and host presence or character. Instead, the leaf shape appears to be affected by environmental conditions including the season. Although our study was limited to a single Boquila genotype and an ecologically unrealistic host selection, our observations suggest that the alleged mimicry might originate from unintentional misinterpretation of intrinsic discontinuous leaf shape plasticity in field observations.

plant biology↗

bioRxiv2026

A plasmodesmata-specific exocyst complex regulates symplastic connectivity by affecting callose turnover

Plasmodesmata are intercellular channels that mediate symplastic communication between plant cells. Molecular transport through these channels is critically regulated by dynamic callose deposition and degradation, yet the secretory mechanisms that deliver regulatory components to plasmodesmata remain poorly understood. Here, we identify and characterize a non-canonical plasmodesmata-associated module of the exocyst, an evolutionarily conserved protein complex involved in secretory vesicle tethering and exocytosis. Exocyst subunits EXO70G1, SEC15A, EXO84C, and SEC10A specifically accumulate at plasmodesmata, whereas the canonical exocyst subunits EXO70A1 and SEC8 do not. Genetic and interaction analyses show that EXO70G1 acts as a landmark for recruiting SEC15A and EXO84C to plasmodesmata, revealing a distinct mode of exocyst targeting at these membrane domains. EXO70G1-dependent exocyst targeting to plasmodesmata depends on phosphoinositides and sphingolipids, consistent with the specialized lipid environment of plasmodesmal membranes. Loss of EXO70G1 results in increased callose accumulation and reduced symplastic transport, and strongly enhances developmental defects of a callose-overproducing mutant. In addition, exo70G1 mutants display enhanced resistance to bacterial pathogen Pseudomonas syringae, linking reduced plasmodesmal permeability to anti-bacterial defense. Cross-species analysis further indicates that plasmodesmata association is a derived feature of the EXO70G clade, present in angiosperms but absent from non-angiosperm EXO70 homologs. Together, our findings show that exocyst diversification in plants has generated a specialized trafficking module - plasmodesmata-associated exocyst - that links vesicle delivery to callose homeostasis at plasmodesmata, thereby regulating intercellular communication, development, and immunity. TeaserA specialized secretion module of the exocyst complex regulates plant cell-to-cell connectivity by controlling callose turnover at plasmodesmata

plant biology↗

bioRxiv2025

The Tonoplast Topology Index - a new metric for describing vacuole organization

BackgroundThe plant vacuole arises by orchestrated interplay of membrane trafficking, cytoskeletal rearrangements and a variety of signalling pathways. In the root, the characteristic large central vacuole develops by endomembrane reorganization occurring mainly in the transition zone. The vacuoles bounding membrane - the tonoplast - can be visualized in vivo using fluorescent protein markers, allowing for quantitative analysis of confocal microscopy images. Tonoplast organization can thus serve as a sensitive indicator of changes to any of the processes involved in vacuole biogenesis. The Vacuolar Morphology Index (VMI) is widely accepted as a quantitative measure of vacuole structure. However, this metric has two drawbacks - it only reflects the size of the largest vacuolar compartment (missing therefore possible differences in the organization of smaller compartments), and its determination is labor intensive, limiting its use on large datasets. ResultsWe developed an alternative metric for describing vacuole organization, named the Tonoplast Topology Index (TTI), which overcomes the above-mentioned shortcomings of the VMI. We compared the performance of our protocol with VMI on a simulated dataset and on real data. To validate the methods performance, we used it to confirm the previously reported differences in vacuole shape and size between Arabidopsis thaliana roots grown on the surface of an agar medium compared to those embedded inside the agar. Both VMI and TTI could efficiently detect the relatively subtle changes in vacuole organization depending on the position of the root in the agar, and provided correlated results. However, only TTI produced data with close to normal value distribution, simplifying subsequent statistical evaluation. ConclusionsWe present the protocol for TTI determination as a two-stage semi-automated procedure involving microscopic image analysis employing an ImageJ macro and subsequent processing of numeric data in the Jupyter Notebook environment, together with benchmarking image data. Since this implementation is freeware-based, platform-independent and (relatively) user-friendly, we hope it will find its use as a high throughput, added value alternative to the VMI metric.

plant biology↗

bioRxiv2024

The Arabidopsis Class I formin AtFH5 contributes to seedling resistance to salt stress.

The family of formins, evolutionarily conserved multidomain proteins engaged in the control of actin and microtubule cytoskeleton organization, exhibits considerable diversity in plants. Angiosperms have two formin clades consisting of multiple paralogs, Class I and Class II, the former being often transmembrane proteins located at the plasmalemma or endomembranes. According to available transcriptome data, the Arabidopsis thaliana Class I transmembrane formin AtFH5 (At5g54650) exhibits a distinct pattern of transcript abundance in various seedling root tissues with massive increase of transcript level upon salinity stress. To examine a possible role of AtFH5 in NaCl stress response, we generated transgenic plants expressing green fluorescent protein (GFP)-tagged AtFH5 under its native promoter and characterized its tissue and intracellular localization under standard culture conditions and under NaCl stress. While we confirmed the induction of AtFH5 expression by salt treatment, the distribution of tagged protein, with maxima in the border-like cells of the root cap, in the phloem and at lateral root emergence sites, did not reflect previously reported transcript abundance, suggesting posttranscriptional regulation of gene expression. Subcellular localization studies employing also membrane trafficking inhibitors suggested that AtFH5 protein level may be modulated by endocytosis and autophagy. Notably, loss-of-function atfh5 mutants exhibited increased sensitivity to NaCl stress, indicating that AtFH5 contributes to the development of seedling salt tolerance. These findings highlight the functional importance of AtFH5 in abiotic stress responses.

plant biology↗

bioRxiv2024

A genome-wide association screen for genes affecting leaf trichome development and epidermal metal accumulation in Arabidopsis

To identify novel genes engaged in plant epidermal development, we characterized the phenotypic variability of rosette leaf epidermis of 310 sequenced Arabidopsis thaliana accessions, focusing on trichome shape and distribution, compositional characteristics of the trichome cell wall, and histologically detectable metal ion distribution. Some of these traits correlated with climate parameters of ourq accessions locations of origin, suggesting environmental selection. A novel metal deposition pattern in stomatal guard cells was observed in some accessions. Subsequent GWAS analysis identified 1546 loci with protein sequence-altering SNPs associated with one or more traits, including 5 genes with previously reported relevant mutant phenotypes and 80 additional genes with known or predicted roles in relevant developmental and cellular processes. Some candidates, including GFS9/TT9, exhibited environmentally correlated allele distribution. Several large gene families, namely DUF674, DUF784, DUF1262, DUF1985, DUF3741, cytochrome P450, receptor-like kinases, Cys/His-rich C1 domain proteins and formins were overrepresented among the candidates for various traits, suggesting epidermal development-related functions. A possible participation of formins in guard cell metal deposition was supported by observations in available loss of function mutants. Screening of candidate gene lists against the STRING interactome database uncovered several predominantly nuclear protein interaction networks with possible novel roles in epidermal development.

plant biology↗

bioRxiv2019

EXO70A2 is critical for the exocyst complex function in Arabidopsis pollen

Pollen development, pollen grain germination and pollen tube elongation are crucial biological processes in angiosperm plants that need precise regulation to deliver sperm cells to fertilize ovules. Pollen grains undergo two major developmental switches: dehydration characterized by metabolic quiescent state, and rehydration upon pollination that leads to extraordinary metabolic and membrane trafficking activity, resulting in germination and rapid tip growth of pollen tubes. To sustain these processes, many plant housekeeping genes evolved their pollen-specific paralogs. Highly polarized secretion at a growing pollen tube tip requires the exocyst tethering complex responsible for specific targeting of secretory vesicles to the plasma membrane. Here, we describe that EXO70A2 (At5g52340) is the main exocyst EXO70 isoform in Arabidopsis pollen, which governs the conventional secretory function of the exocyst, analogically to EXO70A1 (At5g03540) in the sporophyte. Our analysis of a CRISPR-generated exo70a2 mutant revealed that EXO70A2 is essential for efficient pollen maturation, pollen grain germination and pollen tube growth. GFP:EXO70A2 was localized similarly to other exocyst subunits to the apical domain in growing pollen tube tips characterized by intensive exocytosis. Moreover, EXO70A2 could substitute for the EXO70A1 function in the sporophyte, indicating functional redundancy of these two closely related isoforms. Phylogenetic analysis revealed that the ancient duplication of EXO70A to two (or more) paralogs, one of which is highly expressed in pollen, occurred independently in monocots and dicots. In summary, EXO70A2 is a crucial component of the exocyst complex in the Arabidopsis pollen required for efficient plant sexual reproduction.

plant biology↗

bioRxiv2018

Arabidopsis class I formin FH1 relocates between membrane compartments during root cell ontogeny and associates with plasmodesmata

Formins are evolutionarily conserved eukaryotic proteins engaged in actin nucleation and other aspects of cytoskeletal organization. Angiosperms have two formin clades with multiple paralogs; typical plant Class I formins are integral membrane proteins that can anchor cytoskeletal structures to membranes. For the main Arabidopsis housekeeping Class I formin, FH1 (At3g25500), plasmalemma localization was documented in heterologous expression and overexpression studies. We previously showed that loss of FH1 function increases cotyledon epidermal pavement cell shape complexity via modification of actin and microtubule organization and dynamics. Here we employ transgenic Arabidopsis expressing green fluorescent protein-tagged FH1 (FH1-GFP) from its native promoter to investigate in vivo behaviour of this formin using advanced microscopy techniques. The fusion protein is functional, since its expression complements the fh1 loss-of-function mutant phenotype. Accidental overexpression of FH1-GFP results in a decrease in trichome branch number, while fh1 mutation has the opposite effect, indicating a general role of this formin in controlling cell shape complexity. Consistent with previous reports, FH1-GFP associates with membranes. However, the protein exhibits surprising actin- and secretory pathway-dependent dynamic localization and relocates between cellular endomembranes and the plasmalemma during cell division and differentiation in root tissues, with transient tonoplast localization at the transition/elongation zones border. FH1-GFP also accumulates in actin-rich regions of cortical cytoplasm and associates with plasmodesmata in both the cotyledon epidermis and root tissues. Together with previous reports from metazoan systems, this suggests that formins might have an ancestral role at cell-cell junctions.

plant biology↗