Cortical Cell Layers Research Articles

An atlas of Brachypodium distachyon lateral root development.

The root system of plants is a vital part for successful development and adaptation to different soil types and environments. A major determinant of the shape of a plant root system is the formation of lateral roots, allowing for expansion of the root system. Arabidopsis thaliana, with its simple root anatomy, has been extensively studied to reveal the genetic program underlying root branching. However, to get a more general understanding of lateral root development, comparative studies in species with a more complex root anatomy are required. Here, by combining optimized clearing methods and histology, we describe an atlas of lateral root development in Brachypodium distachyon, a wild, temperate grass species. We show that lateral roots initiate from enlarged phloem pole pericycle cells and that the overlying endodermis reactivates its cell cycle and eventually forms the root cap. In addition, auxin signaling reported by the DR5 reporter was not detected in the phloem pole pericycle cells or young primordia. In contrast, auxin signaling was activated in the overlying cortical cell layers, including the exodermis. Thus, Brachypodium is a valuable model to investigate how signaling pathways and cellular responses have been repurposed to facilitate lateral root organogenesis.

Gibberellin dynamics governing nodulation revealed using GIBBERELLIN PERCEPTION SENSOR 2 in Medicago truncatula lateral organs.

During nutrient scarcity, plants can adapt their developmental strategy to maximize their chance of survival. Such plasticity in development is underpinned by hormonal regulation, which mediates the relationship between environmental cues and developmental outputs. In legumes, endosymbiosis with nitrogen-fixing bacteria (rhizobia) is a key adaptation for supplying the plant with nitrogen in the form of ammonium. Rhizobia are housed in lateral root-derived organs termed nodules that maintain an environment conducive to Nitrogenase in these bacteria. Several phytohormones are important for regulating the formation of nodules, with both positive and negative roles proposed for gibberellin (GA). In this study, we determine the cellular location and function of bioactive GA during nodule organogenesis using a genetically encoded second-generation GA biosensor, GIBBERELLIN PERCEPTION SENSOR 2 in Medicago truncatula. We find endogenous bioactive GA accumulates locally at the site of nodule primordia, increasing dramatically in the cortical cell layers, persisting through cell divisions, and maintaining accumulation in the mature nodule meristem. We show, through misexpression of GA-catabolic enzymes that suppress GA accumulation, that GA acts as a positive regulator of nodule growth and development. Furthermore, increasing or decreasing GA through perturbation of biosynthesis gene expression can increase or decrease the size of nodules, respectively. This is unique from lateral root formation, a developmental program that shares common organogenesis regulators. We link GA to a wider gene regulatory program by showing that nodule-identity genes induce and sustain GA accumulation necessary for proper nodule formation.

Golgi-localized APYRASE 1 is critical for Arabidopsis growth by affecting cell wall integrity under boron deficiency.

Many nucleoside triphosphate-diphosphohydrolases (NTPDases/APYRASEs, APYs) play a key role in modulating extracellular nucleotide levels. However, the Golgi-localized APYs, which help control glycosylation, have rarely been studied. Here, we identified AtAPY1, a gene encoding an NTPDase in the Golgi apparatus, which is required for cell wall integrity and plant growth under boron (B) limited availability. Loss of function in AtAPY1 hindered cell elongation and division in root tips while increasing the number of cortical cell layers, leading to swelling of the root tip and abundant root hairs under low B stress. Further, expression pattern analysis revealed that B deficiency significantly induced AtAPY1, especially in the root meristem and stele. Fluorescent-labeled AtAPY1-GFP localized to the Golgi stack. Biochemical analysis showed that AtAPY1 exhibited a preference of UDP and GDP hydrolysis activities. Consequently, the loss of function in AtAPY1 might disturb the homoeostasis of NMP-driven NDP-sugar transport, which was closely related to the synthesis of cell wall polysaccharides. Further, cell wall-composition analysis showed that pectin content increased and borate-dimerized RG-II decreased in apy1 mutants, along with a decrease in cellulose content. Eventually, altered polysaccharide characteristics presumably cause growth defects in apy1 mutants under B deficiency. Altogether, these data strongly support a novel role for AtAPY1 in mediating responses to low B availability by regulating cell wall integrity.

Spatiotemporal expression of thyroid hormone transporter MCT8 and THRA mRNA in human cerebral organoids recapitulating first trimester cortex development

Thyroid hormones (TH) play critical roles during nervous system development and patients carrying coding variants of MCT8 (monocarboxylate transporter 8) or THRA (thyroid hormone receptor alpha) present a spectrum of neurological phenotypes resulting from perturbed local TH action during early brain development. Recently, human cerebral organoids (hCOs) emerged as powerful in vitro tools for disease modelling recapitulating key aspects of early human cortex development. To begin exploring prospects of this model for thyroid research, we performed a detailed characterization of the spatiotemporal expression of MCT8 and THRA in developing hCOs. Immunostaining showed MCT8 membrane expression in neuronal progenitor cell types including early neuroepithelial cells, radial glia cells (RGCs), intermediate progenitors and outer RGCs. In addition, we detected robust MCT8 protein expression in deep layer and upper layer neurons. Spatiotemporal SLC16A2 mRNA expression, detected by fluorescent in situ hybridization (FISH), was highly concordant with MCT8 protein expression across cortical cell layers. FISH detected THRA mRNA expression already in neuroepithelium before the onset of neurogenesis. THRA mRNA expression remained low in the ventricular zone, increased in the subventricular zone whereas strong THRA expression was observed in excitatory neurons. In combination with a robust up-regulation of known T3 response genes following T3 treatment, these observations show that hCOs provide a promising and experimentally tractable model to probe local TH action during human cortical neurogenesis and eventually to model the consequences of impaired TH function for early cortex development.

The peptide GOLVEN10 alters root development and noduletaxis in Medicago truncatula.

The conservation of GOLVEN (GLV)/ROOT MERISTEM GROWTH FACTOR (RGF) peptide encoding genes across plant genomes capable of forming roots or root-like structures underscores their potential significance in the terrestrial adaptation of plants. This study investigates the function and role of GOLVEN peptide-coding genes in Medicago truncatula. Five out of fifteen GLV/RGF genes were notably upregulated during nodule organogenesis and were differentially responsive to nitrogen deficiency and auxin treatment. Specifically, the expression of MtGLV9 and MtGLV10 at nodule initiation sites was contingent upon the NODULE INCEPTION transcription factor. Overexpression of these five nodule-induced GLV genes in hairy roots of M. truncatula and application of their synthetic peptide analogues led to a decrease in nodule count by 25-50%. Uniquely, the GOLVEN10 peptide altered the positioning of the first formed lateral root and nodule on the primary root axis, an observation we term 'noduletaxis'; this decreased the length of the lateral organ formation zone on roots. Histological section of roots treated with synthetic GOLVEN10 peptide revealed an increased cell number within the root cortical cell layers without a corresponding increase in cell length, leading to an elongation of the root likely introducing a spatiotemporal delay in organ formation. At the transcription level, the GOLVEN10 peptide suppressed expression of microtubule-related genes and exerted its effects by changing expression of a large subset of Auxin responsive genes. These findings advance our understanding of the molecular mechanisms by which GOLVEN peptides modulate root morphology, nodule ontogeny, and interactions with key transcriptional pathways.

Molecular phylogeny and genetic diversity of the economic seaweed Meristotheca (Gigartinales, Rhodophyta) in the northwest Pacific, with a description of M. pilulaora sp. nov

AbstractSpecies of the red algal genus Meristotheca are important natural resources that can be used directly as food for human consumption as well as raw materials for the extraction of carrageenan. Despite being harvested in Japan and Korea, a comprehensive taxonomic study of Meristotheca specimens from these two countries to elucidate their phylogenetic position is lacking. In this study, we aimed to clarify the taxonomic identities of specimens currently regarded as M. papulosa from Korea and Japan by analyzing morphological and molecular data. As the result, we recognized a new species, Meristotheca pilulaora sp. nov. from Korea and resurrected Meristotheca japonica for specimens from Japan. The two entities have long been identified as M. papulosa and exhibit similar external morphologies. They appeared independently in the concatenated phylogenetic tree of COI-5P and rbcL and could also be distinguished morphologically by the position of cystocarps (blade margins in M. pilulaora; marginal proliferations in M. japonica), spinose cystocarps (absent in M. pilulaora; present in M. japonica), and the number of cortical cell layers (two in M. pilulaora; 4–8 in M. japonica). The DNA analysis of M. pilulaora sp. nov. in local populations showed 11 COI-5P haplotypes on Jeju Island with no apparent geographical structure. High genetic diversity and occurrence of unique haplotypes in southern Jeju may provide a genetic basis for population with high thermal tolerance. These findings have strengthened our understanding of the species diversity of the genus Meristotheca and provided insights into conservation, management, and haplotype selection for the future cultivation of these economically important species.

Small peptide signaling via OsCIF1/2 mediates Casparian strip formation at the root endodermal and nonendodermal cell layers in rice.

The Casparian strip (CS) is a ring-like lignin structure deposited between endodermal cells that forms an apoplastic barrier to control the selective uptake of nutrients in vascular plants. However, the molecular mechanism of CS formation in rice (Oryza sativa), which possesses one CS each in the endodermis and exodermis, is relatively unknown. Here, we functionally characterized CS INTEGRITY FACTOR1 (OsCIF1a, OsCIF1b), OsCIF2, and SCHENGEN3 (OsSGN3a, OsSGN3b) in rice. OsCIF1s and OsCIF2 were mainly expressed in the stele, while OsSGN3s localized around the CS at the endodermis. Knockout of all three OsCIFs or both OsSGN3s resulted in a discontinuous CS and a dramatic reduction in compensatory (less localized) lignification and suberization at the endodermis. By contrast, ectopic overexpression of OsCIF1 or OsCIF2 induced CS formation as well as overlignification and oversuberization at single or double cortical cell layers adjacent to the endodermis. Ectopic co-overexpression of OsCIF1 and SHORTROOT1 (OsSHR1) induced the formation of more CS-like structures at multiple cortical cell layers. Transcriptome analysis identified 112 downstream genes modulated by the OsCIF1/2-OsSGN3 signaling pathway, which is involved in CS formation and activation of the compensatory machinery in native endodermis and nonnative endodermis-like cell layers. Our results provide important insights into the molecular mechanism of CIF-mediated CS formation at the root endodermal and nonendodermal cell layers.

Transcellular progression of infection threads in Medicago truncatula roots is associated with locally confined cell wall modifications

The root nodule symbiosis with its global impact on nitrogen fertilization of soils is characterized by an intracellular colonization of legume roots by rhizobia. Although the symbionts are initially taken up by morphologically adapted root hairs, rhizobia persistently progress within a membrane-confined infection thread through several root cortical and later nodular cell layers. Throughout this transcellular passaging, rhizobia have to repeatedly pass host plasma membranes and cell walls. Here, we investigated this essential process and describe the concerted action of one of the symbiosis-specific pectin methyl esterases (SyPME1) and the nodulation pectate lyase (NPL) at the infection thread and transcellular passage sites. Their coordinated function mediates spatially confined pectin alterations in the cell-cell interface that result in the establishment of an apoplastic compartment where bacteria are temporarily released into and taken up from the subjacent cell. This process allows successful intracellular progression of infection threads through the entire root cortical tissue.

Auxin triggers pectin modification during rootlet emergence in white lupin.

Emergence of secondary roots through parental tissue is a highly controlled developmental process. Although the model plant Arabidopsis has been useful to uncover the predominant role of auxin in this process, its simple root structure is not representative of how emergence takes place in most plants, which display more complex root anatomy. White lupin is a legume crop producing structures called cluster roots, where closely spaced rootlets emerge synchronously. Rootlet primordia push their way through several cortical cell layers while maintaining the parent root integrity, reflecting more generally the lateral root emergence process in most multilayered species. In this study, we showed that lupin rootlet emergence is associated with an upregulation of cell wall pectin modifying and degrading genes under the active control of auxin. Among them, we identified LaPG3, a polygalacturonase gene typically expressed in cells surrounding the rootlet primordium and we showed that its downregulation delays emergence. Immunolabeling of pectin epitopes and their quantification uncovered a gradual pectin demethylesterification in the emergence zone, which was further enhanced by auxin treatment, revealing a direct hormonal control of cell wall properties. We also report rhamnogalacturonan-I modifications affecting cortical cells that undergo separation as a consequence of primordium outgrowth. In conclusion, we describe a model of how external tissues in front of rootlet primordia display cell wall modifications to allow for the passage of newly formed rootlets.

Differential influence of cortex and stele components on root tip diameter in different types of tropical climbing plants.

Climbing plants are an abundant and taxonomically diverse plant group that competes intensely with trees and thus substantially affects forest diversity and structure. The growth and physiology of climbing plants largely depend on their root tip structure and function. However, little is known regarding the mechanisms through which anatomical traits regulate root tip diameter in climbing plants. Therefore, our study sought to explore the relationships between root tip diameter and seven anatomical traits (e.g., cortex thickness and stele diameter) in three lianas and three vine species sampled from a tropical forest in Hainan. Root tip diameter was significantly positively correlated with cortex thickness (r = 0.94–0.99) and stele diameter (r = 0.72–0.94) within species, especially with cortex thickness. Cortex thickness was significantly positively correlated with mean cortical cell diameter in six species (r = 0.72–0.93), but was only correlated with the number of cortical cell layers in three species (r = 0.42–0.66). Stele diameter displayed significant positive correlations with mean conduit diameter (r = 0.58–0.88) and the number of conduits per stele (r = 0.50–0.66, except for Cyclea hypoglauca), and was negatively correlated with conduit density in all species (r = −0.65 to –0.77). The correlations between cortical cells and conduit traits and root tip diameter were similar to that with cortex thickness and stele diameter, respectively. Compared with vines, liana root tips showed closer relationships between root diameter and cortex thickness and stele diameter, and between cortex thickness and mean diameter of cortical cells. Moreover, the root tip of lianas possesses significantly higher stele proportion and denser conduits, significantly lower cortex proportion, and smaller conduit size than those of vines. However, the specific conductivity was similar. Overall, these results suggest that the cortex is the main driver for the change in root tip diameter rather than the stele. Nevertheless, both factors were responsible for variations in diameter-related traits when compared with number-related traits, with lianas and vines exhibiting distinct regulatory mechanisms.

Altered Topographic Distribution and Enhanced Neuronal Expression of Adenosine-Metabolizing Enzymes in Rat Hippocampus and Cortex from Early to late Adulthood.

The present study demonstrates altered topographic distribution and enhanced neuronal expression of major adenosine-metabolizing enzymes, i.e. ecto-5'-nucleotidase (eN) and tissue non-specific alkaline phosphatase (TNAP), as well as adenosine receptor subtype A2A in the hippocampus and cortex of male rats from early to late adulthood (3, 6, 12 and 15 months old males). The significant effect of age was demonstrated for the increase in the activity and the protein expression of eN and TNAP. At 15-m, enzyme histochemistry demonstrated enhanced expression of eN in synapse-rich hippocampal and cortical layers, whereas the upsurge of TNAP was observed in the hippocampal and cortical neuropil, rather than in cells and layers where two enzymes mostly reside in 3-m old brain. Furthermore, a dichotomy in A1R and A2AR expression was demonstrated in the cortex and hippocampus from early to late adulthood. Specifically, a decrease in A1R and enhancement of A2AR expression were demonstrated by immunohistochemistry, the latter being almost exclusively localized in hippocampal pyramidal and cortical superficial cell layers. We did not observe any glial upregulation of A2AR, which was common for both advanced age and chronic neurodegeneration. Taken together, the results imply that the adaptative changes in adenosine signaling occurring in neuronal elements early in life may be responsible for the later prominent glial enhancement in A2AR-mediated adenosine signaling, and neuroinflammation and neurodegeneration, which are the hallmarks of both advanced age and age-associated neurodegenerative diseases.

Bioenergy sorghum’s deep roots: A key to sustainable biomass production on annual cropland

AbstractBioenergy sorghum has high biomass yield potential, drought resilience, good nitrogen use efficiency, and a root system that contributes to the accumulation of soil organic carbon. In this study, field grown bioenergy sorghum root systems were analyzed during the growing season to characterize their depth, biomass, morphology, anatomy, and gene expression profiles. Bioenergy sorghum roots grew continuously during a 155‐day growing season producing ~175 nodal roots, accumulating ~7 Mg of dry biomass per hectare, and reaching >2 m deep in the soil profile. Nodal roots within 20 cm of the stem were 1–5 mm in diameter, whereas roots deeper in soil profiles were enriched in lateral roots with small diameters (~30–500 µm) enabling growth through soil macropores. In older field‐grown plants, roots with intact endodermal, vascular and inner root tissues were surrounded by degraded or aerenchyma‐filled epidermal and cortical cell layers. Transcriptome analysis of nodal, surface, and deep roots identified >2,500 differentially expressed genes involved in root growth, transport, adaptation, defense, and AMF–root interaction. Deep roots (180–240 cm) differentially expressed genes that regulate lateral root growth. Surface roots (0–20 cm) located mid‐row differentially expressed genes involved in nitrate transport, whereas ammonium transport genes were expressed in surface and deep roots and genes involved in phosphate transport were expressed in nodal, surface, and deep roots. Overall, bioenergy sorghum's long growing season enables root systems to grow deeper and accumulate more biomass than annual grain crops such as maize, attributes that could help restore annual cropland soil organic carbon levels and improve soil productivity. Deep roots active in nutrient transport are positioned to take‐up fertilizer leached deep into soil profiles mitigating potential nutrient run‐off. Bioenergy sorghum's large and deep root system is a key to sustainable production of biofuels, biopower, and bioproducts on annual cropland.

Tissue-specific signatures of metabolites and proteins in asparagus roots and exudates

Comprehensive untargeted and targeted analysis of root exudate composition has advanced our understanding of rhizosphere processes. However, little is known about exudate spatial distribution and regulation. We studied the specific metabolite signatures of asparagus root exudates, root outer (epidermis and exodermis), and root inner tissues (cortex and vasculature). The greatest differences were found between exudates and root tissues. In total, 263 non-redundant metabolites were identified as significantly differentially abundant between the three root fractions, with the majority being enriched in the root exudate and/or outer tissue and annotated as ‘lipids and lipid-like molecules’ or ‘phenylpropanoids and polyketides’. Spatial distribution was verified for three selected compounds using MALDI-TOF mass spectrometry imaging. Tissue-specific proteome analysis related root tissue-specific metabolite distributions and rhizodeposition with underlying biosynthetic pathways and transport mechanisms. The proteomes of root outer and inner tissues were spatially very distinct, in agreement with the fundamental differences between their functions and structures. According to KEGG pathway analysis, the outer tissue proteome was characterized by a high abundance of proteins related to ‘lipid metabolism’, ‘biosynthesis of other secondary metabolites’ and ‘transport and catabolism’, reflecting its main functions of providing a hydrophobic barrier, secreting secondary metabolites, and mediating water and nutrient uptake. Proteins more abundant in the inner tissue related to ‘transcription’, ‘translation’ and ‘folding, sorting and degradation’, in accord with the high activity of cortical and vasculature cell layers in growth- and development-related processes. In summary, asparagus root fractions accumulate specific metabolites. This expands our knowledge of tissue-specific plant cell function.

AP2/ERF transcription factors orchestrate very long chain fatty acid biosynthesis during Arabidopsis lateral root development

AP2/ERF transcription factors orchestrate very long chain fatty acid biosynthesis during Arabidopsis lateral root development

Three-photon imaging of synthetic dyes in deep layers of the neocortex

Multiphoton microscopy has emerged as the primary imaging tool for studying the structural and functional dynamics of neural circuits in brain tissue, which is highly scattering to light. Recently, three-photon microscopy has enabled high-resolution fluorescence imaging of neurons in deeper brain areas that lie beyond the reach of conventional two-photon microscopy, which is typically limited to ~ 450 µm. Three-photon imaging of neuronal calcium signals, through the genetically-encoded calcium indicator GCaMP6, has been used to successfully record neuronal activity in deeper neocortical layers and parts of the hippocampus in rodents. Bulk-loading cells in deeper cortical layers with synthetic calcium indicators could provide an alternative strategy for labelling that obviates dependence on viral tropism and promoter penetration, particularly in non-rodent species. Here we report a strategy for visualized injection of a calcium dye, Oregon Green BAPTA-1 AM (OGB-1 AM), at 500–600 µm below the surface of the mouse visual cortex in vivo. We demonstrate successful OGB-1 AM loading of cells in cortical layers 5–6 and subsequent three-photon imaging of orientation- and direction- selective visual responses from these cells.

Concise review of the genus Dictyota J.V. Lamouroux

The genus Dictyota (Dictyotales, Phaeophyceae) comprises parenchymatous algae occurring predominantly in tropical to warm-temperate waters and has gathered attention due to its diverse secondary metabolites with antibiofouling and pharmaceutical potential, its oil content, and its potential as animal feed. This has resulted in an increase in economic potential during the last decade. In this review, we summarise the recent knowledge on the genus and concentrate on the applications and the economic potential of Dictyota. In addition, the review summarises the taxonomy, anatomy, cytology, genetic data, life history, chemical composition, nutritional value and ecological and economic importance of Dictyota species. Currently, around 100 species are recognised together with the morphologically similar and closely related genera Dilophus, Canistrocarpus and Rugulopteryx (tribus Dictyoteae). The thallus is characterised by one or more lens-shaped apical cells that divide into cortical and medullary cell layers. Species typically grow in rocky intertidal pools and subtidal areas. Dictyota is consumed locally in the Caribbean, Malayan-Indonesian and Hawaiian regions. Extracts of Dictyota which contain active compounds, such as diterpenes and phlorotannins, have been attributed antimicrobial, health and wellness promoting effects which render them promising candidates for the design of functional foods, phytomedicinal products, and cosmetics. The high fraction of lipids and fatty acids has propelled emerging applications in the biofuel industry and as a feedstock species.

The unique expression profile of FAM19A1 in the mouse brain and its association with hyperactivity, long-term memory and fear acquisition

Neurodevelopment and mature brain function are spatiotemporally regulated by various cytokines and chemokines. The chemokine-like neuropeptide FAM19A1 is a member of family with sequence similarity 19 (FAM19), which is predominantly expressed in the brain. Its highly conserved amino acid sequence among vertebrates suggests that FAM19A1 may play important physiological roles in neurodevelopment and brain function. Here we used a LacZ reporter gene system to map the expression pattern of the FAM19A1 gene in the mouse brain. The FAM19A1 expression was observed in several brain regions starting during embryonic brain development. As the brain matured, the FAM19A1 expression was detected in the pyramidal cells of cortical layers 2/3 and 5 and in several limbic areas, including the hippocampus and the amygdala. FAM19A1-deficient mice were used to evaluate the physiological contribution of FAM19A1 to various brain functions. In behavior analysis, FAM19A1-deficient mice exhibited several abnormal behaviors, including hyperactive locomotor behavior, long-term memory deficits and fear acquisition failure. These findings provide insight into the potential contributions of FAM19A1 to neurodevelopment and mature brain function.

A comparative study on physiological responses to drought in walnut genotypes (RX1, Vlach, VX211) commercially available as rootstocks

Walnut production in California depends on the performance of three clonal hybrid rootstocks, and this study provides evidence that roots of genotype RX1 exhibit unique properties to cope with water stress induced by drought. Three hybrid genotypes RX1 (Juglans microcarpa × J. regia), Vlach and VX211 (both J. hindsii × J. regia) are the most commonly used rootstocks for walnut production in California. These rootstocks provide various levels of disease resistance, but their performance under drought is unknown. Based on our findings on xylem stress physiology of native walnut species, we hypothesize that hybrid genotypes originating from wild species native to drier habitats will exhibit superior root performance under drought stress. Using a whole-plant experimental approach, we evaluated root and canopy physiological characteristics of 2-year-old tree saplings of RX1, Vlach and VX211 under two soil moisture treatments (‘control’ 70–90% and ‘drought’ 20–40% w/w soil moisture). In control saplings, root biomass was twofold smaller in RX1 as compared to VX211, but root system hydraulic conductance (Kro, predominantly cell-to-cell pathway) was more than 50% greater in RX1 and Vlach as compared to VX211. The relatively low Kro of VX211 was related to a larger number of root cortical cell layers and endodermis development. In drought-stressed saplings, root biomass was reduced by 27% (P < 0.05) in VX211 but no significant reduction in root biomass was detected in RX1 and Vlach. Maintenance of root biomass under drought in RX1 and Vlach was associated with an 80% decrease in Kro, a threefold increase in leaf intrinsic water-use efficiency, and maintenance of leaf turgor as compared to control conditions. Drought-induced reductions in Kro were linked to the formation of a multiseriate root endodermis in all three genotypes.

Effect of Aluminum Stress on Onion (Allium cepa L.)

This study analyzed the effect of Aluminium (Al) on onion (Allium cepa) root growth and its defense response. The experiment was carried out by exposing onion to 10, 100, 500 and 1000 µM AlCl3 for 24, 48 and 72 hour. Parameters observed were root length and diameter, root tip mitotic index, cortical parenchyma cell length and cortical cell layer thickness. Onion defense response observed by measuring mallic, citric and oxalic acid quantitatively, and the accumulation of Al and callose in root qualitatively. Results showed that an increase in the concentration of Al caused a decrease in root length. At concentrations up to 100 µM, Al increased root diameter cell length whilst at higher concentrations, Al decreased both parameters. Compared to control, all Al-treated root had lower index mitosis with 10 uM Al-treated root displayed highest IM. Since root treated with Al higher than 10 µM showed none or very low mitotic activity, chromosome aberration can only be observed in 10 uM Al–treated roots. Root defense response via Al and callose accumulation was increased with the increasing of Al concentrations. Organic acids were present in higher amounts in root than in medium with a ratio of 5000:1. Oxalic acid appeared to be the major organic acid that played a role in defense mechanisms against Al stress. Based on the results, it can be concluded that (1) Al3+ were toxic to Allium cepa because it caused root growth inhibition and chromosomal aberrations; (2) defense response for Al3+ stress were via the increase of callose as well as Al accumulation and organic acids content in root cells.

P16-T Early signs of transformation of neocortical activity to epileptiform patterns in experimental model of epilepsy

This study was aimed at receiving information concerning organization of the cortical cellular activity in relation to the epileptiform EEG patterns, using ionic model of experimental formation of epileptic focus. This investigation was supported by the KBN grant, Nr4-T11E-006-22. Evaluation of the relationship between EEG patterns and cellular activity was attempted in the region of parietal association cortex (middle suprasylvian gyrus) in the group of five adult cats. Multiunit cellular activity was recorded with sampling frequency 4 kHz, using permanently implanted multicontact concentric electrode: 16 contacts, each about 40 micrometers of diameter and the distance between contacts of 200 micrometers. The electrode was implanted in the vicinity of cannula enabling subdural transfer of artificial cerebrospinal fluid with increased concentration of potassium ions. The recording and perfusion was performed in quiet, awake animal without necessity of using any pharmacological treatment. Early signs of transformation of neocortical activity to epileptiform patterns show considerable degree of independence of the patterns of cellular activity with respect to EEG. The incident of increased intensity and generalization of cellular activity creates the development of variable, irregular superficial electric fields within wide frequency range. This early stage of transformation of cortical activity to epileptiform patterns ends with the appearance of definite patterns of cellular activity, predominantly in internal cortical cell layers with corresponding EEG slow waves and/or spikes. The results suggest the possibility of existence of transient “paroxysmal” cellular activities without coexistence of standard epileptiform patterns in EEG records.