Outer Layers Of Cortex Research Articles

Comparative Phenotypic, Genomic, and Transcriptomic Analyses of Two Contrasting Strains of the Plant Beneficial Fungus Trichoderma virens.

Trichoderma virens is a beneficial fungus that helps plants fight pathogens and abiotic stresses and thereby enhances crop yields. Unlike other Trichoderma spp., there are two well-defined strains (P and Q) of T. virens, classified by secondary metabolites profiling, primarily the biosynthesis of the nonribosomal, strong antimicrobial agents gliotoxin (Q) and gliovirin (P). We have studied the phenotypic and biocontrol properties of two well-studied representative isolates (T. virens Gv29-8 and T. virens GvW/IMI304061) that represent a Q strain and a P strain of T. virens, respectively. We refined the genome assembly of the P strain using nanopore technology, and we compared it with the Q strain. The differences between the genomes include gene expansion in the Q strain. T. virens Gv29-8 is weaker than GvW as a mycoparasite on the broad host-range plant pathogen Sclerotium rolfsii, and it is ineffective as a biocontrol agent when applied to pathogen-infested soil. T. virens Gv29-8 proved to be phytotoxic to Arabidopsis seedlings, whereas the effect of T. virens GvW was not major. Both strains colonized the surface and outer cortex layer of tomato roots, with about 40% higher colonization by T. virens Gv29-8. T. virens Gv29-8 induced the expression of a larger set of tomato genes than did T. virens GvW, although some tomato genes were uniquely induced in response to T. virens GvW. We studied the comparative transcriptome response of T. virens Gv29-8 and T. virens GvW to S. rolfsii. A larger set of genes was regulated in T. virens GvW than in T. virens Gv29-8 in the presence of the plant pathogen. IMPORTANCE Trichoderma virens populations that were earlier classified into two strains (P and Q) based on secondary metabolites profiling are also phenotypically and genetically distinct, with the latter being ineffective in controlling the devastating, broad host range plant pathogen Sclerotium rolfsii. The two strains also provoke distinct as well as overlapping transcriptional responses to the presence of the plant and the pathogen. This study enriches our knowledge of Trichoderma-plant-pathogen interactions and identifies novel candidate genes for further research and deployment in agriculture.

Possible Mechanism of Sex Determination in Mammals

It is known that undifferentiated embryonic gonads (UEG) in embryos of mammals have a dual nature. They consist of an outer layer of cortex, from which in the process of differentiation develop female sex cells, and from the inner layer – medulla – develop male gametes. During the determination of sex, one of the layers of the gonad develops and the other is suppressed. Therefore, the sex of the future fetus depends on which of the tissue cells - medulla or cortex - survives in the UEG. However, almost nothing is known about the causes for the survival of the medulla or cortex.We believe that, perhaps, the main cause for the development of one of the layers of the gonad and the suppression of the other is cell thermoregulation. The survival of the tissue cells of medulla depends on whether they can avoid heat death, which is determined by their ability to effectively remove excess metabolic heat from the cell nucleus. Since excess thermal energy is released into the cytoplasm through a dense layer of condensed chromatin around the nucleus, consisting predominantly of chromosomal constitutive heterochromatin regions (cHR), the fate of the medulla directly depends on the cHR in its cells.Seemingly, the sex in mammals and human is determined by the cHR on Y chromosomes. It is important not so much the amount of cHR on Y chromosome as its localization in the interphase cell around the nucleoli. Thanks to this localization, excess heat is more effectively removed from the "hottest" point of the nucleus, where ribosomes are formed, which is also necessary for the production of proteins that inhibit the development of cortex cells. Otherwise medulla doomed to degeneration and a cortex tissue will remain in the UEG.

OsHAC1;1 and OsHAC1;2 Function as Arsenate Reductases and Regulate Arsenic Accumulation.

Rice is a major dietary source of the toxic metalloid arsenic (As). Reducing its accumulation in rice (Oryza sativa) grain is of critical importance to food safety. Rice roots take up arsenate and arsenite depending on the prevailing soil conditions. The first step of arsenate detoxification is its reduction to arsenite, but the enzyme(s) catalyzing this reaction in rice remains unknown. Here, we identify OsHAC1;1 and OsHAC1;2 as arsenate reductases in rice. OsHAC1;1 and OsHAC1;2 are able to complement an Escherichia coli mutant lacking the endogenous arsenate reductase and to reduce arsenate to arsenite. OsHAC1:1 and OsHAC1;2 are predominantly expressed in roots, with OsHAC1;1 being abundant in the epidermis, root hairs, and pericycle cells while OsHAC1;2 is abundant in the epidermis, outer layers of cortex, and endodermis cells. Expression of the two genes was induced by arsenate exposure. Knocking out OsHAC1;1 or OsHAC1;2 decreased the reduction of arsenate to arsenite in roots, reducing arsenite efflux to the external medium. Loss of arsenite efflux was also associated with increased As accumulation in shoots. Greater effects were observed in a double mutant of the two genes. In contrast, overexpression of either OsHAC1;1 or OsHAC1;2 increased arsenite efflux, reduced As accumulation, and enhanced arsenate tolerance. When grown under aerobic soil conditions, overexpression of either OsHAC1;1 or OsHAC1;2 also decreased As accumulation in rice grain, whereas grain As increased in the knockout mutants. We conclude that OsHAC1;1 and OsHAC1;2 are arsenate reductases that play an important role in restricting As accumulation in rice shoots and grain.

Speciation and localization of Zn in the hyperaccumulator Sedum alfredii by extended X-ray absorption fine structure and micro-X-ray fluorescence

Differences in metal homeostasis among related plant species can give important information of metal hyperaccumulation mechanisms. Speciation and distribution of Zn were investigated in a hyperaccumulating population of Sedum alfredii by using extended X-ray absorption fine structure and micro-synchrotron X-ray fluorescence (μ-XRF), respectively. The hyperaccumulator uses complexation with oxygen donor ligands for Zn storage in leaves and stems, and variations in the Zn speciation was noted in different tissues. The dominant chemical form of Zn in leaves was most probably a complex with malate, the most prevalent organic acid in S. alfredii leaves. In stems, Zn was mainly associated with malate and cell walls, while Zn–citrate and Zn–cell wall complexes dominated in the roots. Two-dimensional μ-XRF images revealed age-dependent differences in Zn localization in S. alfredii stems and leaves. In old leaves of S. alfredii, Zn was high in the midrib, margin regions and the petiole, whereas distribution of Zn was essentially uniform in young leaves. Zinc was preferentially sequestered by cells near vascular bundles in young stems, but was highly localized to vascular bundles and the outer cortex layer of old stems. The results suggest that tissue- and age-dependent variations of Zn speciation and distribution occurred in the hyperaccumulator S. alfredii, with most of the Zn complexed with malate in the leaves, but a shift to cell wall– and citric acid–Zn complexes during transportation and storage in stems and roots. This implies that biotransformation in Zn complexation occurred during transportation and storage processes in the plants of S. alfredii.

백더덕, 홍더덕, 청더덕의 외부형태적 특성 및 유전적 차이 분석

In general, the root color of Codonopsis lanceolata is white, but red or blue-colored root is found at a low frequency in nature. Red or blue-colored roots have scarcity value, thus farmers wish to produce colored roots. The factors for determining the color of roots are unclear whether the color is controlled by genetically or simply by environmentally such as soil environment. Using in vitro culture system which is advantageous for setting of the same culture condition, we analyzed the physiological and morphological characteristics and genetic differences among red-, blue- and white lines of C. lanceolata. In the red colored roots, stems of in vitro cultured plantlet were colored in dark red pigment. Histological analysis revealed that the red pigment was accumulated in the outer cortex layer of the stem and determined as anthocyanin. Chlorophyll contents in red root lines were higher than those in white- and blue root lines. Plantlets from red roots were smaller in both shoot length and total leaf area than those from white- and blue roots. Genetic differences among the three different colored C. lanceolata were determined by RAPD (Randomly Amplified Polymorphic DNA) analysis. Each line of colored roots had clear DNA polymorphism. These results indicate that the occurrence of red- and blue colored roots in nature was determined by genetic factors rather than soil enviromental conditions.

Ultrastructure of cyst shell and underlying membranes of three strains of the brine shrimp Artemia (Branchiopoda: Anostraca) from South India

The cyst of Artemia has shell and membranous coverings over the embryo. The membranous coverings have special adaptive features to allow the physical changes accompanying repeated hydration and dehydration cycles that might occur and adversely influence postembryonic development. Whole and slices of cryptobiotic cysts were processed for electron microscopy to study the internal details and to compare the morphological architecture of three Artemia strains of South India. Surface topography of scanning electron microscopic (SEM) studies revealed distinct button shaped structures on the cyst of Puthalam strain. Transmission electron microscopic (TEM) studies of the cysts displayed the conventional pattern of anostracan crustaceans with outer cortex and alveolar layer, cuticular membranes, and the cytoplasmic inclusions namely nucleus, yolk droplets, lipoid bodies, and mitochondria. The prominent wavy outer cortex layer of Puthalam cysts corroborates the results of SEM studies.

Differential phosphorylation at Ser473 and Thr308 of Akt-1 in rat brain following hypoglycemic coma

We analyzed both total Akt-1 and phosphorylation of Akt-1 at residues Ser473 and Thr308 (phospho-Akt-1 Ser474 and phospho-Akt-1 Thr308, respectively) in the outer and inner layers of cortex following 30 min of hypoglycemic coma by Western blot analyses and confocal microscopy. The total amount of Akt-1 was not altered in any area examined. Phospho-Akt-1 Ser474, however, increased significantly in both layers of cortex at 0 and 30 min of recovery, but returned to control level at 3 h of recovery. In the vulnerable area (outer layer of cortex), no upregulation of phospho-Akt-1 Thr308 was observed at any time points examined. In the resistant area like inner layer of cortex, however, phospho-Akt-1 Thr308 was significantly over the control level at 3 h of recovery. Confocal microscopy result indicates that most of phospho-Akt-1 Thr308 had already moved into nucleus at 3 h of recovery. Our results suggest that Akt-1, when phosphorlyted at Thr308, may play a protective role for neurons in the resistant regions of the brain.

Aluminum induces changes in the orientation of microtubules and the division plane in root meristem of Zea mays

Aluminum (Al) induces agricultural problems limiting crop productivity in acid soils. Since Al causes morphological changes in roots, and because microtubules (MTs) play important roles in determination of tissue morphology, we investigated whether Al affects the arrangement of MTs in maize root meristem using immunolocalization techniques. When seedling roots were treated with 50 μM Al, the orientations of MTs were dramatically altered in a population of cells located in the protoderm and the two outer layers of cortex: interphase cortical MT arrays lost their normal transverse organization and became random or longitudinal; the preprophase band of MTs, mitotic spindle, and phragmoplast developed at planes 90° rotated compared to their counterparts in controls. These changes in MT orientation resulted in the change of the division plane from transverse to longitudinal, producing daughter cells positioned side by side instead of above and below. The rotation of the otherwise normal MT arrays and the division plane in Al-treated roots indicates that Al interferes with the normal polarity sensing mechanism, which may contribute to the reduced axial growth of the Al-treated roots.

Subterranean structures and mycotrophy of the achlorophyllous Triuris hyalina (Triuridaceae)

Triuris hyalina Miers, an unusual achlorophyllous plant, was investigated for subterranean morphology, root anatomy, and mycotrophy. Stems with scale leaves extend subterraneously to a depth of 15 cm. Pairs of adventitious roots develop at the scale leaves and clumps of apparently radiating roots, formed by accumulations of side shoot and scale leaf developments, occur. Roots consist of epidermis, short cell exodermis, three distinct layers of cortex parenchyma, endodermis, and an extremely reduced central cylinder with one or two central tracheidal xylem elements. The fungus associated with T. hyalina roots exhibits thick-walled, 6-9 µm thick, aseptate external hyphae. It penetrates the epidermis by developing appressoria and enters the cortex solely through the short cells of the exodermis. In the cortex cells, the aseptate hyphae start to coil. In the outer cortex layer, hyphae are thin, frequently branched, and most densely coiled. In the middle cortex layer they are thicker and less densely coiled, and mostly appear degenerated to clumps of amorphous fungal material. The inner cortex layer rarely becomes colonized. Vesicles occur in the outer and the middle cortex layers. This mycorrhizal pattern is interpreted as an adaption to attain a sustainable use from the endophyte. It is suggested that the mycorrhiza in Triuris hyalina be interpreted as a type of arbuscular mycorrhiza (AM). Implications for systematics and ecology are discussed.Key words: Triuris, Triuridaceae, root structure, anatomy, arbuscular mycorrhiza, myco-heterotrophy.

CP-101,606, a potent neuroprotectant selective for forebrain neurons

The neuroprotective activity of (1 S,2 S)-1-(4-hydroxyphenyl)-2-(4-hydroxy-4-phenylpiperidino)-1-propanol (CP-101,606), an N-methyl- d-aspartate (NMDA) receptor antagonist structurally similar to ((±)-( R *, S *)-α-(4-hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidineethanol (ifenprodil), was investigated in neurons in primary culture. CP-101,606 potently and efficaciously protected hippocampal neurons from glutamate toxicity but was >900-fold less effective for cerebellar granule neurons. The neuroprotective activity in the hippocampal neurons is mediated through a high affinity binding site distinct from the agonist and thienylcyclohexylpiperidine (TCP) binding sites of the NMDA receptor. Autoradiography indicates the CP-101,606 binding site is localized in forebrain, most notably in hippocampus and the outer layers of cortex. The functional selectivity for hippocampal neurons, forebrain localization of binding sites, and structural relation to ifenprodil suggest that CP-101,606 is an NMDA antagonist highly selective for NR2B subunit containing receptors.

Development of callosal connections in the sensorimotor cortex of the hamster.

To investigate the development of corpus callosal connectivity in the hamster sensorimotor cortex, we have used the sensitive axonal tracer 1,1 dioctadecyl-3,3,3',3', tetramethylindocarbocyanine perchlorate (DiI), which was injected either in vivo or in fixed brains of animals 3-6 days postnatal. First, to study changes in the overall distribution of developing callosal afferents we made large injections of DiI into the corpus callosal tract. We found that the anterogradely labeled callosal axons formed a patchy distribution in the contralateral sensorimotor cortex, which was similar to the pattern of adult connectivity described in earlier studies of the rodent corpus callosum. This result stands in contrast to previous retrograde studies of developing callosal connectivity which showed that the distribution of callosal neurons early in development is homogeneous and that the mature, patchy distribution arises later, primarily as a result of the retraction of exuberant axons. The initial patchy distribution of callosal axon growth into the sensorimotor cortex described in the present study suggests that exuberant axons destined to be eliminated do not enter the cortex. In addition, small injections of DiI into developing cortex resulted in homotopic patterns of callosal topography in which reciprocal regions of sensorimotor cortex are connected, as has been shown in the adult. Second, to study the radial growth of callosal afferents we followed the extension of individual callosal axons into the developing cortex. We found that callosal axons began to invade the contralateral cortex on about postnatal day 3, with little or no waiting period in the callosal tract. Callosal afferents then advanced steadily through the cortex, never actually invading the cortical plate but extending into layers on the first day that they could be distinguished from the cortical plate. The majority of callosal axons grew radially through the cortex and did not exhibit substantial branching until postnatal day 8, the age when the cortical plate disappears and callosal afferents reach the outer layer of cortex. This mode of radial growth through cortex prior to axon branching could serve to align callosal afferents with their radial or columnar targets before arborizing laterally.

Ultrasonic absorption in mammalian ovaries

The human ovary, as well as that of other mammalian species, has the opportunity to receive ultrasonic exposure during diagnostic and therapeutic procedures. However, the ultrasonic absorption behavior seems never to have been investigated. Such information is considered essential for both safety and treatment planning. The ovary is a dynamic organ exhibiting interspecies variation as well as variation among the intraovarian structures, viz., the follicles, corpora lutea, etc. The in vitro ultrasonic absorption coefficient was determined, by the transient thermoelectric method, for ovaries of bovine, canine, feline, ovine, and murine species at 1 MHz. Similarities in values exist for intraovarian structures among the species measured. For example, of the stromal tissues, the outer cortex layer exhibits absorption coefficients approximately 50% greater than that of the inner medulla. The follicle absorption is the lowest and the corpora lutea values vary with the stage of development. These results are consistent with the macromolecular composition of these structures. [Work supported by the NIH.]

APICAL ORGANIZATION IN ROOTS OF THE CONVOLVULACEAE

A sampling of radicles and germinated primary roots was obtained for several species of the Convolvulaceae in order to study ontogenetically the organization of the protomeristem. The findings differ from earlier studies in that only a few radicles and primary roots exhibited proto‐meristems with layered initials. Most radicles exhibited a pattern of layered initials in which the outer cell layers of cortex were not aligned with a layer of cortical initials but with cells at the base of the columella. In long primary roots the protomeristem, consisting of central cylinder initials, lateral rootcap‐epidermal initials, and common initials for the cortex and columella, was the general pattern for the members of the family. The reorganization of the protomeristem from a layered condition to common initials generally occurred upon germination. Different expressions of intermediate patterns indicated that periclinal divisions in the outer layers of cortex near the initials or in the immediate derivatives of the cortical initials were responsible for cellular displacements and new cell alignments. After reorganization, periclinal divisions in the peripheral portions of the common initials maintained the cellular continuity from the cortex into the columella. In addition, a few primary roots with a degenerated columella and a transversal meristem were observed.