Plant cell morphogenesis involves concerted rearrangements of microtubules and actin microfilaments. We previously reported that FH1, the main Arabidopsis thaliana housekeeping Class I membrane-anchored formin, contributes to actin dynamics and microtubule stability in rhizodermis cells. Here we examine the effects of mutations affecting FH1 (At3g25500) on cell morphogenesis and above-ground organ development in seedlings, as well as on cytoskeletal organization and dynamics, using a combination of confocal and variable angle epifluorescence microscopy with a pharmacological approach. Homozygous fh1 mutants exhibited cotyledon epinasty and had larger cotyledon pavement cells with more pronounced lobes than the wild type. The pavement cell shape alterations were enhanced by expression of the fluorescent microtubule marker GFP-microtubule-associated protein 4 (MAP4). Mutant cotyledon pavement cells exhibited reduced density and increased stability of microfilament bundles, as well as enhanced dynamics of microtubules. Analogous results were also obtained upon treatments with the formin inhibitor SMIFH2 (small molecule inhibitor of formin homology 2 domains). Pavement cell shape in wild-type (wt) and fh1 plants in some situations exhibited a differential response towards anti-cytoskeletal drugs, especially the microtubule disruptor oryzalin. Our observations indicate that FH1 participates in the control of microtubule dynamics, possibly via its effects on actin, subsequently influencing cell morphogenesis and macroscopic organ development.
- MeSH
- Actins metabolism MeSH
- Arabidopsis cytology drug effects metabolism MeSH
- Biomarkers metabolism MeSH
- Models, Biological MeSH
- Cytoskeleton drug effects metabolism MeSH
- Fluorescence MeSH
- Clathrin metabolism MeSH
- Cotyledon drug effects metabolism MeSH
- Membrane Proteins metabolism MeSH
- Actin Cytoskeleton drug effects metabolism MeSH
- Microtubules drug effects metabolism MeSH
- Mutation genetics MeSH
- Arabidopsis Proteins metabolism MeSH
- Seedlings drug effects growth & development metabolism MeSH
- Thiones pharmacology MeSH
- Cell Shape * drug effects MeSH
- Uracil analogs & derivatives pharmacology MeSH
- Green Fluorescent Proteins metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
BACKGROUND AND AIMS: Stomatal density (SD) generally decreases with rising atmospheric CO2 concentration, Ca. However, SD is also affected by light, air humidity and drought, all under systemic signalling from older leaves. This makes our understanding of how Ca controls SD incomplete. This study tested the hypotheses that SD is affected by the internal CO2 concentration of the leaf, Ci, rather than Ca, and that cotyledons, as the first plant assimilation organs, lack the systemic signal. METHODS: Sunflower (Helianthus annuus), beech (Fagus sylvatica), arabidopsis (Arabidopsis thaliana) and garden cress (Lepidium sativum) were grown under contrasting environmental conditions that affected Ci while Ca was kept constant. The SD, pavement cell density (PCD) and stomatal index (SI) responses to Ci in cotyledons and the first leaves of garden cress were compared. (13)C abundance (δ(13)C) in leaf dry matter was used to estimate the effective Ci during leaf development. The SD was estimated from leaf imprints. KEY RESULTS: SD correlated negatively with Ci in leaves of all four species and under three different treatments (irradiance, abscisic acid and osmotic stress). PCD in arabidopsis and garden cress responded similarly, so that SI was largely unaffected. However, SD and PCD of cotyledons were insensitive to Ci, indicating an essential role for systemic signalling. CONCLUSIONS: It is proposed that Ci or a Ci-linked factor plays an important role in modulating SD and PCD during epidermis development and leaf expansion. The absence of a Ci-SD relationship in the cotyledons of garden cress indicates the key role of lower-insertion CO2 assimilation organs in signal perception and its long-distance transport.
- MeSH
- Arabidopsis cytology drug effects MeSH
- Fagus cytology drug effects MeSH
- Dehydration MeSH
- Helianthus cytology drug effects MeSH
- Cotyledon drug effects physiology MeSH
- Lepidium cytology drug effects MeSH
- Carbon Dioxide pharmacology MeSH
- Cell Count MeSH
- Plant Stomata cytology drug effects MeSH
- Environment MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Background and Aim: The cytoskeleton plays an important role in the synthesis of plant cell walls. Both microtubules and actin cytoskeleton are known to be involved in the morphogenesis of plant cells through their role in cell wall building. The role of ARP2/3-nucleated actin cytoskeleton in the morphogenesis of cotyledon pavement cells has been described before. Seedlings of Arabidopsis mutants lacking a functional ARP2/3 complex display specific cell wall-associated defects. Methods: In three independent Arabidopsis mutant lines lacking subunits of the ARP2/3 complex, phenotypes associated with the loss of the complex were analysed throughout plant development. Organ size and anatomy, cell wall composition, and auxin distribution were investigated. Key Results: ARP2/3-related phenotype is associated with changes in cell wall composition, and the phenotype is manifested especially in mature tissues. Cell walls of mature plants contain less cellulose and a higher amount of homogalacturonan, and display changes in cell wall lignification. Vascular bundles of mutant inflorescence stems show a changed pattern of AUX1-YFP expression. Plants lacking a functional ARP2/3 complex have decreased basipetal auxin transport. Conclusions: The results suggest that the ARP2/3 complex has a morphogenetic function related to cell wall synthesis and auxin transport.
- MeSH
- Arabidopsis genetics metabolism MeSH
- Cell Wall metabolism MeSH
- Actin-Related Protein 2-3 Complex genetics metabolism MeSH
- Indoleacetic Acids metabolism MeSH
- Arabidopsis Proteins genetics metabolism MeSH
- Plant Growth Regulators metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
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 behavior 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 a shared (ancestral or convergent) role at cell-cell junctions.
Development of the plant aerial organs epidermis involves a complex interplay of cytoskeletal rearrangements, membrane trafficking-dependent cell surface expansion, and intra- and intercellular signaling, resulting in a pattern of perfectly interlocking pavement cells. While recent detailed in vivo observations convincingly identify microtubules rather than actin as key players at the early stages of development of pavement cell lobes in Arabidopsis, mutations affecting the actin-nucleating ARP2/3 complex are long known to reduce pavement cell lobing, suggesting a central role for actin. We have now shown that functional impairment of the Arabidopsis formin FH1 enhances both microtubule dynamics and pavement cell lobing. While formins are best known for their ability to nucleate actin, many members of this old gene family now emerge as direct or indirect regulators of the microtubule cytoskeleton, and our findings suggest that they might co-ordinate action of the two cytoskeletal systems during pavement cell morphogenesis.
- MeSH
- Arabidopsis growth & development metabolism ultrastructure MeSH
- Models, Biological MeSH
- Cytoskeleton metabolism physiology ultrastructure MeSH
- Membrane Proteins genetics metabolism physiology MeSH
- Microtubules metabolism physiology ultrastructure MeSH
- Multigene Family MeSH
- Arabidopsis Proteins genetics metabolism physiology MeSH
- Plant Cells metabolism ultrastructure MeSH
- Signal Transduction MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
V práci je prezentována krátká kazuistika vlastního bioptického případu pacienta s chronickou urocystitidou způsobenou infekcící motolicí Schistosoma haematobium. Dále následuje přehled nejčastějších morfologických forem urogenitální schistosomózy, jejích komplikací a možností patologické diferenciální diagnostiky, sestavený na podkladě literárních údajů (vč. údajů z dostupných elektronických databází), zabývajících se patomorfologií a zvláště histopatologií urogenitální schistosomózy. V rámci obecných histopatologických změn se objevují leze odpovídající aktivní chronické infekci s převažující granulomatózní reakcí. Později dochází ke kalcifikaci, tvorbě pseudotumorózních polypózních formací, ulcerací, fibroobliterativních lézí, transformací epitělu typu hyperplíizii, metaplazií i dysplazií. Na tyto změny navazují v jednotlivých topikách různorodé klinické i morfologické komplikace, od posthemoragických anémií přes adheze, závažné obstrukce vývodných cest urogenitálu a jejich následky, až po zvýšené riziko vzniku dlaždicobuněčného karcinomu močového měchýře. Z výše uvedených důvodů je nutné zařadit možnost urogenitální schistosomózy do širší skupiny klinických i patologických diferenciálně diagnostických rozvah při určování etiologie a terapie zánětlivých i tumorózních lézí v této lokalizaci.
The authors submit the case history of their patient presenting with chronic cystitis, consequence of an infestatiom with the fluke Schistosoma haematobium. They also present the most frequent morphological forms of urogenital schistosomiasis, its complications and the possibilities of pathological differential diagnosis, based on literary data (including information from elecronic data bases) on the pathomorphology and, more particularly, the histopathology of urogenital schistosomiasis. Among the general histopathological changes we see lesions that correspond to an active chronic infection with a chiefly granulomatous reaction. Calcification, pseudotumorous polypoid formations, ulcerations, obliterating fibrous lesions, epithelial transformations such as hyperplasia, metaplasia and dysplasia follow later. These changes are followed at the various sites by diverse clinical and morphological complications - posthaemorrhagic anaemia, adhesions, serious obstructions of urogenital openings and its consequences and, finally, an increased risk of pavement-cell carcinoma of the bladder. Eor all the above-mentioned reasons we should include the possibility of urogenital schistosomiasis into the large group of clinical and pathological aspects of differential diagnosis, when considering the etiology and treatment of inflammatory and tumorous lesions of the urogenital tract.
- MeSH
- Urinary Tract Infections complications parasitology pathology MeSH
- Humans MeSH
- Schistosomiasis diagnosis complications parasitology MeSH
- Animals MeSH
- Check Tag
- Humans MeSH
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Case Reports MeSH
