Outermost Cell Research Articles

The Polygonal Cell Shape and Surface Protein Layer of Anaerobic Methane-Oxidizing Methylomirabilis lanthanidiphila Bacteria.

Methylomirabilis bacteria perform anaerobic methane oxidation coupled to nitrite reduction via an intra-aerobic pathway, producing carbon dioxide and dinitrogen gas. These diderm bacteria possess an unusual polygonal cell shape with sharp ridges that run along the cell body. Previously, a putative surface protein layer (S-layer) was observed as the outermost cell layer of these bacteria. We hypothesized that this S-layer is the determining factor for their polygonal cell shape. Therefore, we enriched the S-layer from M. lanthanidiphila cells and through LC-MS/MS identified a 31 kDa candidate S-layer protein, mela_00855, which had no homology to any other known protein. Antibodies were generated against a synthesized peptide derived from the mela_00855 protein sequence and used in immunogold localization to verify its identity and location. Both on thin sections of M. lanthanidiphila cells and in negative-stained enriched S-layer patches, the immunogold localization identified mela_00855 as the S-layer protein. Using electron cryo-tomography and sub-tomogram averaging of S-layer patches, we observed that the S-layer has a hexagonal symmetry. Cryo-tomography of whole cells showed that the S-layer and the outer membrane, but not the peptidoglycan layer and the cytoplasmic membrane, exhibited the polygonal shape. Moreover, the S-layer consisted of multiple rigid sheets that partially overlapped, most likely giving rise to the unique polygonal cell shape. These characteristics make the S-layer of M. lanthanidiphila a distinctive and intriguing case to study.

The lipid-binding START domain regulates the dimerization of ATML1 via modulating the ZIP motif activity in Arabidopsis thaliana.

In Arabidopsis thaliana, the epidermis is the outermost cell layer composed of many specialized types of epidermal cells, such as pavement cells, trichomes, and guard cells. The homeodomain-leucine zipper (HD-ZIP) class Ⅳ transcription factors (TFs), which are unique to the plant kingdom, have been recognized as key regulators of epidermis development. Unlike animal HD proteins, which can bind to DNA as monomers, plant HD-ZIP class Ⅳ TFs bind to DNA as dimers, although little is known about the regulation of their dimerization process. Here, we show that the homodimerization of ARABIDOPSIS THALIANA MERISTEM LAYER 1 (ATML1) - HD-ZIP class Ⅳ TF that is required for protoderm development - is regulated by the lipid-binding steroidogenic acute regulatory protein-related lipid transfer (START) domain. We found that ATML1 forms homodimer through interaction via its ZIP motif in yeast and plant cells, although the interaction is abolished by generating a mutation into the lipid-binding START domain to disrupt the lipid-binding ability. These results suggest that lipidic ligands function as key regulators of protoderm development via modulating the dimerization of ATML1.

Crystalline S-Layer Protein Monolayers Induce Water Turbulences on the Nanometer Scale

Bacterial surface layers (S-layers) have been observed as the outermost cell envelope component in a wide range of bacteria and most archaea. They are one of the most common prokaryotic cell surface structures and cover the cells completely. It is assumed that S-layers provide selection advantages to prokaryotic cells in their natural habitats since they act as protective envelopes, as structures involved in cell adhesion and surface recognition, as molecular or ion traps, and as molecular sieves in the ultrafiltration range. In order to contribute to the question of the function of S-layers for the cell, we merged high-resolution cryo-EM and small-angle X-ray scattering datasets to build a coarse-grained functional model of the S-layer protein SbpA from Lysinibacillus sphaericus ATCC 4525. We applied the Navier–Stokes and the Poisson equations for a 2D section through the pore region in the self-assembled SbpA lattice. We calculated the flow field of water, the vorticity, the electrostatic potential, and the electric field of the coarse-grained model. From calculated local changes in the flow profile, evidence is provided that both the characteristic rigidity of the S-layer and the charge distribution determine its rheological properties. The strength of turbulence and pressure near the S-layer surface in the range of 10 to 50 nm thus support our hypothesis that the S-layer, due to its highly ordered repetitive crystalline structure, not only increases the exchange rate of metabolites but is also responsible for the remarkable antifouling properties of the cell surface. In this context, studies on the structure, assembly and function of S-layer proteins are promising for various applications in nanobiotechnology, biomimetics, biomedicine, and molecular nanotechnology.

Characterization of Permeability Barrier Dysfunction in a Murine Model of Cutaneous Field Cancerization Following Chronic UV-B Irradiation: Implications for the Pathogenesis of Skin Cancer.

Simple SummaryIn the present work, we developed an experimental preclinical model of skin with cutaneous field cancerization after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice). We observed impairments in the transepidermal water loss, stratum corneum hydration, and surface pH. We also detected a marked hyperkeratotic hyperplasia of the epidermis, induction of keratinocyte hyperproliferation, incidental actinic keratosis, and in situ squamous cell carcinomas in the UV-B light-irradiated groups. In this context, the association between the permeability barrier impairment and keratinocyte hyperproliferation might be considered a new target in the management of skin with cutaneous field cancerization. As current therapeutic approaches to actinic keratosis and cutaneous field cancerization only focus on the direct antineoplastic, immunomodulatory, or photodynamic effects of approved topical drugs, this mouse model of skin with cutaneous field cancerization might be helpful for both the identification and screening of potentially new preventive strategies or treatments (e.g., skin barrier therapies).Chronic ultraviolet B (UV-B) irradiation is known to be one of the most important hazards acting on the skin and poses a risk of developing photoaging, skin with cutaneous field cancerization (CFC), actinic keratosis (AKs), and squamous cell carcinomas (SCCs). Most of the UV-B light is absorbed in the epidermis, affecting the outermost cell layers, the stratum corneum, and the stratum granulosum, which protects against this radiation and tries to maintain the permeability barrier. In the present work, we show an impairment in the transepidermal water loss, stratum corneum hydration, and surface pH after chronic UV-B light exposure in an immunologically intact mouse model (SKH1 aged mice) of skin with CFC. Macroscopic lesions of AKs and SCCs may develop synchronically or over time on the same cutaneous surface due to both the presence of subclinical AKs and in situ SCC, but also the accumulation of different mutations in keratinocytes. Focusing on skin with CFC, yet without the pathological criteria of AKs or SCC, the presence of p53 immunopositive patches (PIPs) within the epidermis is associated with these UV-B-induced mutations. Reactive epidermis to chronic UV-B exposure correlated with a marked hyperkeratotic hyperplasia, hypergranulosis, and induction of keratinocyte hyperproliferation, while expressing an upregulation of filaggrin, loricrin, and involucrin immunostaining. However, incidental AKs and in situ SCC might show neither hypergranulosis nor upregulation of differentiation markers in the upper epidermis. Despite the overexpression of filaggrin, loricrin, involucrin, lipid enzymes, and ATP-binding cassette subfamily A member 12 (ABCA12) after chronic UV-B irradiation, the permeability barrier, stratum corneum hydration, and surface pH were severely compromised in the skin with CFC. We interpret these results as an attempt to restore the permeability barrier homeostasis by the reactive epidermis, which fails due to ultrastructural losses in stratum corneum integrity, higher pH on skin surface, abundant mast cells in the dermis, and the common presence of incidental AKs and in situ SCC. As far as we know, this is the first time that the permeability barrier has been studied in the skin with CFC in a murine model of SCC induced after chronic UV-B irradiation at high doses. The impairment in the permeability barrier and the consequent keratinocyte hyperproliferation in the skin of CFC might play a role in the physiopathology of AKs and SCCs.

Patterns in Nature—S-Layer Lattices of Bacterial and Archaeal Cells

Bacterial surface layers (S-layers) have been observed as the outermost cell envelope component in a wide range of bacteria and most archaea. S-layers are monomolecular lattices composed of a single protein or glycoprotein species and have either oblique, square or hexagonal lattice symmetry with unit cell dimensions ranging from 3 to 30 nm. They are generally 5 to 10 nm thick (up to 70 nm in archaea) and represent highly porous protein lattices (30–70% porosity) with pores of uniform size and morphology in the range of 2 to 8 nm. Since S-layers can be considered as one of the simplest protein lattices found in nature and the constituent units are probably the most abundantly expressed proteins on earth, it seems justified to briefly review the different S-layer lattice types, the need for lattice imperfections and the discussion of S-layers from the perspective of an isoporous protein network in the ultrafiltration region. Finally, basic research on S-layers laid the foundation for applications in biotechnology, synthetic biology, and biomimetics.

High-resolution spatiotemporal transcriptome analyses during cellularization of rice endosperm unveil the earliest gene regulation critical for aleurone and starchy endosperm cell fate specification

The major tissues of the cereal endosperm are the starchy endosperm (SE) in the inner and the aleurone layer (AL) at the outer periphery. The fates of the cells that comprise these tissues are determined according to positional information; however, our understanding of the underlying molecular mechanisms remains limited. Here, we conducted a high-resolution spatiotemporal analysis of the rice endosperm transcriptome during early cellularization. In rice, endosperm cellularization proceeds in a concentric pattern from a primary alveolus cell layer, such that developmental progression can be defined by the number of cell layers. Using laser-capture microdissection to obtain precise tissue sections, transcriptomic changes were followed through five histologically defined stages of cellularization from the syncytial to 3-cell layer (3L) stage. In addition, transcriptomes were compared between the inner and the outermost peripheral cell layers. Large differences in the transcriptomes between stages and between the inner and the peripheral cells were found. SE attributes were expressed at the alveolus-cell-layer stage but were preferentially activated in the inner cell layers that resulted from periclinal division of the alveolus cell layer. Similarly, AL attributes started to be expressed only after the 2L stage and were localized to the outermost peripheral cell layer. These results indicate that the first periclinal division of the alveolus cell layer is asymmetric at the transcriptome level, and that the cell-fate-specifying positional cues and their perception system are already operating before the first periclinal division. Several genes related to epidermal identity (i.e., type IV homeodomain-leucine zipper genes and wax biosynthetic genes) were also found to be expressed at the syncytial stage, but their expression was localized to the outermost peripheral cell layer from the 2L stage onward. We believe that our findings significantly enhance our knowledge of the mechanisms underlying cell fate specification in rice endosperm.

Investigations by AFM of Ageing Mechanisms in PLA-Flax Fibre Composites during Garden Composting.

PLA-flax non-woven composites are promising materials, coupling high performance and possible degradation at their end of life. To explore their ageing mechanisms during garden composting, microstructural investigations were carried out through scanning electron microscopy (SEM) and atomic force microscopy (AFM). We observe that flax fibres preferentially degrade ‘inwards’ from the edge to the core of the composite. In addition, progressive erosion of the cell walls occurs within the fibres themselves, ‘outwards’ from the central lumen to the periphery primary wall. This preferential degradation is reflected in the decrease in indentation modulus from around 23 GPa for fibres located in the preserved core of the composite to 3–4 GPa for the remaining outer-most cell wall crowns located at the edge of the sample that is in contact with the compost. Ageing of the PLA matrix is less drastic with a relatively stable indentation modulus. Nevertheless, a change in the PLA morphology, a significant decrease in its roughness and increase of porosity, can be observed towards the edge of the sample, in comparison to the core. This work highlights the important role of intrinsic fibre porosity, called lumen, which is suspected to be a major variable of the compost ageing process, providing pathways of entry for moisture and microorganisms that are involved in cell wall degradation.

The Plant Cuticle: An Ancient Guardian Barrier Set Against Long-Standing Rivals.

The aerial surfaces of plants are covered by a protective barrier formed by the cutin polyester and waxes, collectively referred to as the cuticle. Plant cuticles prevent the loss of water, regulate transpiration, and facilitate the transport of gases and solutes. As the cuticle covers the outermost epidermal cell layer, it also acts as the first line of defense against environmental cues and biotic stresses triggered by a large array of pathogens and pests, such as fungi, bacteria, and insects. Numerous studies highlight the cuticle interface as the site of complex molecular interactions between plants and pathogens. Here, we outline the multidimensional roles of cuticle-derived components, namely, epicuticular waxes and cutin monomers, during plant interactions with pathogenic fungi. We describe how certain wax components affect various pre-penetration and infection processes of fungi with different lifestyles, and then shift our focus to the roles played by the cutin monomers that are released from the cuticle owing to the activity of fungal cutinases during the early stages of infection. We discuss how cutin monomers can activate fungal cutinases and initiate the formation of infection organs, the significant impacts of cuticle defects on the nature of plant–fungal interactions, along with the possible mechanisms raised thus far in the debate on how host plants perceive cutin monomers and/or cuticle defects to elicit defense responses.

S-Layer Ultrafiltration Membranes.

Monomolecular arrays of protein subunits forming surface layers (S-layers) are the most common outermost cell envelope components of prokaryotic organisms (bacteria and archaea). Since S-layers are periodic structures, they exhibit identical physicochemical properties for each constituent molecular unit down to the sub-nanometer level. Pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes. The functional groups on the surface and in the pores of the S-layer protein lattice are accessible for chemical modifications and for binding functional molecules in very precise fashion. S-layer ultrafiltration membranes (SUMs) can be produced by depositing S-layer fragments as a coherent (multi)layer on microfiltration membranes. After inter- and intramolecular crosslinking of the composite structure, the chemical and thermal resistance of these membranes was shown to be comparable to polyamide membranes. Chemical modification and/or specific binding of differently sized molecules allow the tuning of the surface properties and molecular sieving characteristics of SUMs. SUMs can be utilized as matrices for the controlled immobilization of functional biomolecules (e.g., ligands, enzymes, antibodies, and antigens) as required for many applications (e.g., biosensors, diagnostics, enzyme- and affinity-membranes). Finally, SUM represent unique supporting structures for stabilizing functional lipid membranes at meso- and macroscopic scale.

A Quarter Century History of ATML1 Gene Research.

The cloning of the ATML1 gene, encoding an HD-ZIP class IV transcription factor, was first reported in 1996. Because ATML1 mRNA was preferentially detected in the shoot epidermis, cis-regulatory sequences of ATML1 have been used to drive gene expression in the outermost cells of the shoot apical meristem and leaves, even before the function of ATML1 was understood. Later studies revealed that ATML1 is required for developmental processes related to shoot epidermal specification and differentiation. Consistent with its central role in epidermal development, ATML1 activity has been revealed to be restricted to the outermost cells via several regulatory mechanisms. In this review, we look back on the history of ATML1 research and provide a perspective for future studies.

Ceramides mediate positional signals in Arabidopsis thaliana protoderm differentiation.

The differentiation of distinct cell types in appropriate patterns is a fundamental process in the development of multicellular organisms. In Arabidopsis thaliana, protoderm/epidermis differentiates as a single cell layer at the outermost position. However, little is known about the molecular nature of the positional signals that achieve correct epidermal cell differentiation. Here, we propose that very-long-chain fatty acid-containing ceramides (VLCFA-Cers) mediate positional signals by stimulating the function of ARABIDOPSIS THALIANA MERISTEM LAYER1 (ATML1), a master regulator of protoderm/epidermis differentiation, during lateral root development. We show that VLCFA-Cers, which are synthesized predominantly in the outermost cells, bind to the lipid-binding domain of ATML1. Importantly, this cell type-specific protein-lipid association alters the activity of ATML1 protein and consequently restricts its expression to the protoderm/epidermis through a transcriptional feedback loop. Furthermore, establishment of a compartment, enriched with VLCFA-containing sphingolipids, at the outer lateral membrane facing the external environment may function as a determinant of protodermal cell fate. Taken together, our results indicate that VLCFA-Cers play a pivotal role in directing protoderm/epidermis differentiation by mediating positional signals to ATML1.This article has an associated 'The people behind the papers' interview.

Glycan-to-Glycan Binding: Molecular Recognition through Polyvalent Interactions Mediates Specific Cell Adhesion.

Glycan-to-glycan binding was shown by biochemical and biophysical measurements to mediate xenogeneic self-recognition and adhesion in sponges, stage-specific cell compaction in mice embryos, and in vitro tumor cell adhesion in mammals. This intermolecular recognition process is accepted as the new paradigm accompanying high-affinity and low valent protein-to-protein and protein-to-glycan binding in cellular interactions. Glycan structures in sponges have novel species-specific sequences. Their common features are the large size >100 kD, polyvalency >100 repeats of the specific self-binding oligosaccharide, the presence of fucose, and sulfated and/or pyruvylated hexoses. These structural and functional properties, different from glycosaminoglycans, inspired their classification under the glyconectin name. The molecular mechanism underlying homophilic glyconectin-to-glyconectin binding relies on highly polyvalent, strong, and structure-specific interactions of small oligosaccharide motifs, possessing ultra-weak self-binding strength and affinity. Glyconectin localization at the glycocalyx outermost cell surface layer suggests their role in the initial recognition and adhesion event during the complex and multistep process. In mammals, Lex-to-Lex homophilic binding is structure-specific and has ultra-weak affinity. Cell adhesion is achieved through highly polyvalent interactions, enabled by clustering of small low valent structure in plasma membranes.

A new morphological marker of the effects of acid rain in the tropics on the stem of

Some of the largest remaining fragments of the Atlantic rainforest are affected by acid rain. Knowing the responses of its native plant species to acidity may be crucial to use them as bioindicators in affected areas. We tested the effects of pH 3.0 simulated acid rain on the stem of Libidibia ferrea (Mart. ex Tul.) L.P. Queiroz var. leiostachya (Benth.) L.P. Queiroz (ironwood, “pau-ferro”). Visual symptomatology consisted in dark spots on the stem that initiated on and irradiated from lenticels. As they grew larger, adjacent spots coalesced, conferring a blackened aspect to a large extension of the organ. Anatomically, the damage started with hypertrophy and increased accumulation of phenolic compounds in the outermost cell layers of the young, still subepidermal cork, which is what conferred the blackened aspect to the stem. In addition, epidermal cells showed turgor loss and ultimately collapsed, resulting in alteration of cell shape and a consequent alteration of epidermal relief. The stem of L. ferrea var. leiostachya was shown to be a more sensitive organ to the impacts of acid rain than the leaf. The dark spots visualised on the stem may be a promising macroscopic marker to be used in the biomonitoring of acid rain.

К. Schaffer: Zur feineren Struktur der Hirnrinde und über funktionelle Bedeutung der Nervenzellenfortsätze. Arch. f. Mikrosk. Anatomie. XLVIIL 4 Heft. 1897. S. S. 550—572

The author's research refers to the anterior cerebral cortex of a newborn dog. The author studies in detail the so-called tiny pyramidal cells, lying between the pluripolar cells of the molecular layer and the small (true) pyramidal cells. Already R. y Cajal drew attention to polygonal or core-shaped cells, the cells that lie behind the layer of the outermost cells (pluripolare Nervenzellen von R. y Cajal), but did not separate them into a special group, believing that these cells were gradually changing vid, go into the small pyramids, to which he numbered them. Schaffer separates these cells into a special group, calling it the layer of surface polymorphic cells. These cells have a dark variety of shapes (fusiform, oval, roundish, pear-shaped, polygonal) and lie in approximately four (4) rows. Dendrites go then, mainly, in two opposite directions (for fusiform cells), then they move radially in all directions (for round and polygonal cells). The number of dendrites is sometimes strikingly abundant. Dendrites going to the surface of the brain reach it, while dendrites of the opposite direction sometimes go down to the ammonium formations of the cerebral cortex. Special attention should be paid to the axial cylinder of the disassembled cells; on the basis of the features of this appendix, the author distinguishes 3 types of disassembled cells.

Polysaccharide length affects mycobacterial cell shape and antibiotic susceptibility.

Bacteria control the length of their polysaccharides, which can control cell viability, physiology, virulence, and immune evasion. Polysaccharide chain length affects immunomodulation, but its impact on bacterial physiology and antibiotic susceptibility was unclear. We probed the consequences of truncating the mycobacterial galactan, an essential linear polysaccharide of about 30 residues. Galactan covalently bridges cell envelope layers, with the outermost cell wall linkage point occurring at residue 12. Reducing galactan chain length by approximately half compromises fitness, alters cell morphology, and increases the potency of hydrophobic antibiotics. Systematic variation of the galactan chain length revealed that it determines periplasm size. Thus, glycan chain length can directly affect cellular physiology and antibiotic activity, and mycobacterial glycans, not proteins, regulate periplasm size.

Lactobacillus strains vary in their ability to interact with human endometrial stromal cells.

The placental membranes that surround the fetus during pregnancy were suggested to contain a low abundance microbiota. Specifically, abundance of Lactobacillus, a probiotic and dominant member of the microbiome of the lower reproductive tract, has been shown to correlate with healthy, term pregnancies. We therefore sought to assess the interactions between four different Lactobacillus strains with immortalized decidualized endometrial cells (dT-HESCs), which were used as a model to represent the outermost layer of the placental membranes. Notably, we demonstrated that all four Lactobacillus strains could associate with dT-HESCs in vitro. L. crispatus was significantly more successful (p < 0.00005), with 10.6% of bacteria attaching to the host cells compared to an average of 0.8% for the remaining three strains. The four strains also varied in their ability to form biofilms. Dependent on media type, L. reuteri 6475 formed the strongest biofilms in vitro. To examine the impact on immune responses, levels of total and phosphorylated protein p38, a member of the Mitogen Activated Protein Kinase (MAPK) pathway, were examined following Lactobacillus association with dT-HESCs. Total levels of p38 were reduced to an average of 44% that of the cells without Lactobacillus (p < 0.05). While a trend towards a reduction in phosphorylated p38 was observed, this difference was not significant (p > 0.05). In addition, association with Lactobacillus did not result in increased host cell death. Collectively, these data suggest that varying types of Lactobacillus can attach to the outermost cells of the placental membranes and that these interactions do not contribute to inflammatory responses or host cell death. To our knowledge this is the first in vitro study to support the ability of Lactobacillus to interact with placental cells, which is important when considering its use as a potential probiotic within the reproductive tract.

Pestalotiopsis desseminata PADA JAMBU MENTE BIOLOGI DAN INTERAKSINYA DENGAN Helopeltis antonii

&lt;p&gt;&lt;strong&gt;Pestalotiopsis desseminata on cashew: its biology and interaction with Helopeltis antonii&lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Pestalotiopsis desseminata is one of pathogens causing leaf spots. die-back of shoots and inflorescence of cashew plant. It is assumed there is an interaction between the attack of Helopeltis antonii and the fungus in Ihe ield so that the damage becomes more devastating. The objectives of (his research were to investigate several aspects of fungal biology (pathogenicity, mycelial growth, acervuli production, sensitivity to fungicides) and its interaction with //. antonii. The esearch was carried out from April 1999 to March 2000 at the laboratory and green house of Pest and Disease Department Research Institute for Spice and Medicinal Crops, Bogor. /' desseminata was diectly isolated from cashew leaves. Pathogenicity test of P. desseminata isolate was conducted on cashew seedlings. The fungal growth and fungicide effects were carried out in vitro on agar medium. The interaction between P. desseminata and H. antonii was examined by inoculating the fungus and insect, either individually or in combination, on cashew seedlings. The results showed that P. desseminata isolate fomis black spherical acervuli containing oblongs conidia with 5 cells, and the outermost cell has 3 flagellate. Acervuli could only be produced on the cultue illuminated continuously by 600 lux translucent lamp. Pathogenicity test of several isolates of /' desseminata on cashew seedlings caused spherical leaf spot symptom, individually or coalesced as bigger leaf spots. In vitro fungal mycelia growth could be suppressed by several fungicides, including bcnomyl 50% (I ppm) and Uiiopanate-mcthyl 70% (10 ppm) Combining inoculation between P. desseminata and //. antonii resulted in moe severe (devastating) die-back compared with individually inoculated.&lt;/p&gt;

Nesting and foraging behavior of Xylocopa valga in the Ejina Oasis, China.

Xylocopa valga is extinct in Latvia and Lithuania and is critically endangered in Poland, and its distribution in the Ejina Oasis, China, is currently unknown. Studies on the biology of X. valga are scarce, and thus, conservation efforts for this species are currently limited. Here, we investigated the morphological characteristics, nest architecture, nest structure and food type of offspring in the nest cells of X. valga. This research was conducted in the Populus euphratica forest reserve in the Ejina Oasis, China, between July 2014 and June 2019. The primary investigation methods included visual inspection, photography, observation and measurements of nest anatomy, and examination of pollen stores by microscopy. We found that in the Ejina Oasis, China, X. valga builds its nests in the dead wood of P. euphratica. X. valga is univoltine. Its lifestyle varies from solitude to symbiosis. When many females nest near each other, several females may share a single nest entrance, based on which they build their own cells. The nests are branched. According to our results, there is a significant difference between the thickness of the inner cell partition and that of the outermost cell partition in the branched tunnel. In the P. euphratica forest area, the food for the progeny of X. valga is mainly composed of the pollen and nectar of Sophora alopecuroide and Populus euphratica. Therefore, X. valga and S. alopecuroides exhibit close ecological interactions in the P. euphratica forest ecosystem.

&lt;p&gt;&lt;strong&gt;&lt;em&gt;Aphanta asiatica&lt;/em&gt;&lt;/strong&gt;&lt;strong&gt; sp. nov. (Orthogonacladiaceae, Rhodophyta), a new species from the Asia-Pacific region with the first description of reproductive structures in this genus&lt;/strong&gt;&lt;/p&gt;

We analyzed mitochondrial COI-5P and plastid rbcL sequences from specimens of Aphanta collected from China and Japan and accessed morpho-anatomical data in detail. The results revealed the presence of a novel species of this genus, Aphanta asiatica, described here. Aphanta asiatica was characterized by a turf-forming habit of thalli with anastomosing branches, and a thick, wide, and flattened axis with subpinnate to pinnate branches, and characterized by its robust and branched prostrate system bearing complex peg-like haptera which were either typical or non-typical. Rhizoidal filaments were abundant in the inner cortex and distal ends of the axis, and interspersed in the medulla. Tetrasporangial and spermatangial sori were produced on the terminal ends of the branchlets and axes. Tetrasporangia were irregularly arranged and cruciately divided, and spermatangia were cut off from the outermost cortical cells. In phylogenies of the COI-5P and rbcL sequences, A. asiatica was closely related to Aphanta pachyrrizha. In conclusion, the present study is the first to document reproductive structures in, and contribute further to our understanding of, the genus Aphanta.

Overexpression of three related root-cap outermost-cell-specific C2H2-type zinc-finger protein genes suppresses the growth of Arabidopsis in an EAR-motif-dependent manner

The root meristem of Arabidopsis thaliana is protected by the root cap, the size of which is tightly regulated by the balance between the formative cell divisions and the dispersal of the outermost cells. We isolated an enhancer-tagged dominant mutant displaying the short and twisted root by the overexpression of ZINC-FINGER OF ARABIDOPSIS THALIANA1 (ZAT1) encoding an EAR motif-containing zinc-finger protein. The growth inhibition by ZAT1 was shared by ZAT4 and ZAT9, the ZAT1 homologues. The ZAT1 promoter was specifically active in the outermost cells of the root cap, in which ZAT1-GFP was localized when expressed by the ZAT1 promoter. The outermost cell-specific expression pattern of ZAT1 was not altered in the sombrero (smb) or smb bearskin1 (brn1) brn2 accumulating additional root-cap layers. In contrast, ZAT4-GFP and ZAT9- GFP fusion proteins were distributed to the inner root-cap cells in addition to the outermost cells where ZAT4 and ZAT9 promoters were active. Overexpression of ZAT1 induced the ectopic expression of PUTATIVE ASPARTIC PROTEASE3 involved in the programmed cell death. The EAR motif was essential for the growth inhibition by ZAT1. These results suggest that the three related ZATs might regulate the maturation of the outermost cells of the root cap.