Pod development of groundnut (Arachis hypogaea L.) in solution culture

Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight.     

Circulating immune complexes in patients with breast cancer.

In a retrospective study in women with breast cancer circulating immune complex levels were measured by radioimmunoprecipitation with 125I-Clq. Before operation all the patients showed plasma immune complex levels significantly higher than those in controls. Twelve months after mastectomy patients identified clinicopathologically as having a good prognosis had almost normal levels of immune complexes. By contrast, patients with detectable dissemination on diagnosis or those who died within 22 months after mastectomy had significantly raised plasma levels. The tumour-specific nature of the immune complexes detected remains to be shown and suggestions about the applicability of this test not only for prognosis but also for monitoring the course of malignant diseases need to be confirmed by further investigations.     

Interspecific differences in aluminium tolerance in relation to root cation-exchange capacity

Genotypic differences in aluminium (Al) tolerance hold considerable promise in overcoming an important limitation to plant growth in acid soils. Little is known, however, about the biochemical basis of such differences. Extracellular properties, particularly low root cation-exchange capacity (CEC), have been associated with Al tolerance, since roots of low CEC adsorb less Al than do those of high CEC. A solution culture study was conducted in which 12 plant species (monocots and dicots) were grown in solution culture of low ionic strength (ca 2 mM) for 8 d at four Al concentrations (0, 16, 28 and 55 M). The species differed significantly in Al tolerance as shown by differences in root length. Root length relative to that of the same species grown in the absence of Al varied from 6 to 117% at 16 M Al, and from 6 to 75% at 28 M Al. Species tolerance of Al was not closely associated with differences in root CEC. Although in some species Al sensitivity was associated with high adsorption of Al during a 10- or 40-min exposure to Al (expressed on a fresh mass or root length basis), this was not a good predictor of Al tolerance across all species studied.     

Distribution and speciation of Mn in hydrated roots of cowpea at levels inhibiting root growth

The phytotoxicity of Mn is important globally due to its increased solubility in acid or waterlogged soils. Short‐term (≤24 h) solution culture studies with 150 µM Mn were conducted to investigate the in situ distribution and speciation of Mn in apical tissues of hydrated roots of cowpea [Vigna unguiculata (L.) Walp. cv. Red Caloona] using synchrotron‐based techniques. Accumulation of Mn was rapid; exposure to 150 µM Mn for only 5 min resulting in substantial Mn accumulation in the root cap and associated mucigel. The highest tissue concentrations of Mn were in the root cap, with linear combination fitting of the data suggesting that ≥80% of this Mn(II) was associated with citrate. Interestingly, although the primary site of Mn toxicity is typically the shoots, concentrations of Mn in the stele of the root were not noticeably higher than in the surrounding cortical tissues in the short‐term (≤24 h). The data provided here from the in situ analyses of hydrated roots exposed to excess Mn are, to our knowledge, the first of this type to be reported for Mn and provide important information regarding plant responses to high Mn in the rooting environment.     

Synchrotron-Based Techniques Shed Light on Mechanisms of Plant Sensitivity and Tolerance to High Manganese in the Root Environment

Plant species differ in response to high available manganese (Mn), but the mechanisms of sensitivity and tolerance are poorly understood. In solution culture, greater than or equal to 30 µm Mn decreased the growth of soybean (Glycine max), but white lupin (Lupinus albus), narrow-leafed lupin (Lupin angustifolius), and sunflower (Helianthus annuus) grew well at 100 µm Mn. Differences in species’ tolerance to high Mn could not be explained simply by differences in root, stem, or leaf Mn status, being 8.6, 17.1, 6.8, and 9.5 mmol kg^–1 leaf fresh mass at 100 µm Mn. Furthermore, x-ray absorption near edge structure analyses identified the predominance of Mn(II), bound mostly to malate or citrate, in roots and stems of all four species. Rather, differences in tolerance were due to variations in Mn distribution and speciation within leaves. In Mn-sensitive soybean, in situ analysis of fresh leaves using x-ray fluorescence microscopy combined with x-ray absorption near edge structure showed high Mn in the veins, and manganite [Mn(III)] accumulated in necrotic lesions apparently through low Mn sequestration in vacuoles or other vesicles. In the two lupin species, most Mn accumulated in vacuoles as either soluble Mn(II) malate or citrate. In sunflower, Mn was sequestered as manganite at the base of nonglandular trichomes. Hence, tolerance to high Mn was ascribed to effective sinks for Mn in leaves, as Mn(II) within vacuoles or through oxidation of Mn(II) to Mn(III) in trichomes. These two mechanisms prevented Mn accumulation in the cytoplasm and apoplast, thereby ensuring tolerance to high Mn in the root environment.Manganese (Mn) is an essential element for plant growth, but its availability differs greatly in space and time, depending largely on the nature and amount of Mn minerals present and on the soil’s pH and redox potential. With an elaborate chemistry, Mn forms complexes with many organic and inorganic ligands. In soils, Mn has three common oxidation states, Mn(II), Mn(III), and Mn(IV), which form hydrated oxides of mixed valency; Mn is present also as numerous carbonates, silicates, sulfates, and phosphates (Lindsay, 1979). Cationic Mn²⁺ is the most common form readily absorbed by plant roots (Clarkson, 1988). The toxicity of Mn occurs in acid or waterlogged soils high in Mn minerals.Many plants have mechanisms to accommodate the large differences in Mn²⁺ in soils. At low available Mn, uptake is increased in some Poaceae by excretion of phytosiderophores of the mugineic acid family (Takahashi et al., 2003), with root phytase exudation also potentially important for acquisition of Mn when Mn availability is limited (George et al., 2014). Mechanisms in other plants include the ability of roots to decrease rhizosphere pH or excrete organic ligands (Neumann and Romheld, 2012; Lambers et al., 2015). However, the relative importance of the many complexes on Mn uptake remains unclear. Toxicity results from high Mn in leaf cell walls (Wissemeier et al., 1992; Wissemeier and Horst, 1992) and through adverse effects on symplastic proteins (Führs et al., 2008). Many plants have mechanisms that limit the adverse effects of high Mn²⁺ in soils, with numerous ligands involved in its translocation and that of other essential cations (Haydon and Cobbett, 2007). Edwards and Asher (1982) classified a range of crop and pasture species based on their ability to deal with high Mn as those that (1) limit Mn from entering the roots, (2) retain Mn in the roots, or (3) tolerate high Mn in the shoots. At the extreme are plants that hyperaccumulate more than 10,000 mg Mn kg^–1 on a dry mass (DM) basis in foliar tissues without metabolic damage (Fernando et al., 2013; van der Ent et al., 2013). Based on 15% DM of leaves, this equates to 12.1 mmol kg^–1 on a fresh mass (FM) basis. Celosia argentia, a species adapted to growth on Mn-contaminated mine tailings, accumulated more than 20,000 mg kg^–1 Mn in leaves (Liu et al., 2014). Tolerance of high Mn in shoots of some Mn hyperaccumulators has been found to occur through binding to ligands (such as malate or citrate) or sequestration in the vacuole (Fernando et al., 2010).Characteristic symptoms of Mn toxicity include chlorotic and distorted leaves with small necrotic lesions. These lesions have been shown in cowpea (Vigna unguiculata) to contain oxidized Mn and callose (Wissemeier et al., 1992), which forms as a reaction to high intracellular Ca (Kartusch, 2003). The necrotic lesions result mainly from oxidized phenolics (Wissemeier and Horst, 1992) and increased peroxidase activity in the apoplast (Horst et al., 1999). With a critical solution concentration for toxicity (10% growth reduction) of no more than 9 µm Mn, Edwards and Asher (1982) found that cotton (Gossypium hirsutum), bean (Phaseolus vulgaris), cowpea, and soybean (Glycine max) were the most sensitive species of 13 crop and pasture plants grown for 18 to 31 d at constant Mn in solution culture. By contrast, the critical concentration for sunflower (Helianthus annuus) was 7 times higher at 65 µm Mn. Sunflower was the first species found to tolerate high Mn through its sequestration in the trichomes on stems, petioles, and leaves (Blamey et al., 1986). The suspected accumulation of Mn was confirmed using wavelength dispersive x-ray spectroscopy with darkening inferred as due to insoluble higher oxides of Mn. Similarly, high Mn results in darkened trichomes of cucumber (Cucumis sativus) leaves due to oxidized Mn, as shown by the colorimetric benzidine test (Horiguchi, 1987). Watermelon (Citrullus lanatus; Elamin and Wilcox, 1986b), but not muskmelon (Citrullus melo; Elamin and Wilcox, 1986a), grown at high Mn also develops small dark spots around the leaf trichomes. Other species that sequester Mn in the trichomes include common nettle (Urtica dioica; Hughes and Williams, 1988) and Alyssum murale, a Ni hyperaccumulator (Broadhurst et al., 2009; McNear and Küpper, 2014). Thus, some plants in four families, Asteraceae, Cucurbitaceae, Urticaceae, and Brassicaceae, tolerate high Mn in shoots through Mn sequestration in or around the trichomes. The mechanisms may differ, however, because the high Mn present during development of common nettle stinging hairs decreases as plants mature (Hughes and Williams, 1988).Recently developed techniques, including those based on synchrotron radiation, allow investigations of the distribution and speciation of Mn in planta, with most research to date focused on Mn hyperaccumulators (Fernando et al., 2013). For example, Fernando et al. (2010) used x-ray absorption near-edge spectroscopy (XANES) to confirm the widely accepted view that Mn(II) predominates in seven Mn hyperaccumulators. Synchrotron-based x-ray fluorescence microspectroscopy (µ-XRF) was used by McNear and Küpper (2014) to show that the basal region of trichomes of A. murale plants grown at no more than 10 µm Mn contained Mn(II) complexed with phosphate. At 50 µm Mn in solution, however, the increased amount of Mn that had accumulated around the trichomes was present as Mn(III). Few studies, however, have used synchrotron-based techniques to investigate the mechanisms of Mn toxicity and tolerance in agronomic species despite their importance for food production in regions where soils are acidic or intermittently waterlogged. One study on cowpea, with a critical toxicity concentration of only 2 µm Mn (Edwards and Asher, 1982), has shown an accumulation of Mn-citrate in the root cap and associated mucigel within 5 min of exposure to 150 µm Mn (Kopittke et al., 2013).This study aimed to determine the distribution and speciation of Mn in fresh roots, stems, and leaves of four crop species, soybean, white lupin (Lupinus albus), narrow-leafed lupin (Lupinus angustifolius), and sunflower, which differ in tolerance to high Mn. It was hypothesized that Mn distribution and speciation would differ between Mn-sensitive soybean and the three other species. Furthermore, we considered it likely that the Mn tolerance mechanism of sunflower would differ from those of the two lupin species, which do not have darkened trichomes when grown at high Mn.     

The crystal structure of calcium- and integrin-binding protein 1: insights into redox regulated functions

Calcium- and integrin-binding protein 1 (CIB1) is involved in the process of platelet aggregation by binding the cytoplasmic tail of the alpha(IIb) subunit of the platelet-specific integrin alpha(Iib)beta(3). Although poorly understood, it is widely believed that CIB1 acts as a global signaling regulator because it is expressed in many tissues that do not express integrin alpha(Iib)beta(3). We report the structure of human CIB1 to a resolution of 2.3 A, crystallized as a dimer. The dimer interface includes an extensive hydrophobic patch in a crystal form with 80% solvent content. Although the dimer form of CIB1 may not be physiologically relevant, this intersub-unit surface is likely to be linked to alpha(IIb) binding and to the binding of other signaling partner proteins. The C-terminal domain of CIB1 is structurally similar to other EF-hand proteins such as calmodulin and calcineurin B. Despite structural homology to the C-terminal domain, the N-terminal domain of CIB1 lacks calcium-binding sites. The structure of CIB1 revealed a complex with a molecule of glutathione in the reduced state bond to the N-terminal domain of one of the two subunits poised to interact with the free thiol of C35. Glutathione bound in this fashion suggests CIB1 may be redox regulated. Next to the bound GSH, the orientation of residues C35, H31, and S48 is suggestive of a cysteine-type protein phosphatase active site. The potential enzymatic activity of CIB1 is discussed and suggests a mechanism by which it regulates a wide variety of proteins in cells in addition to platelets.     

Toxicities of soluble Al, Cu, and La include ruptures to rhizodermal and root cortical cells of cowpea

Elevated levels of many metals are toxic to plant roots, but their modes of action are not well understood. We investigated the toxicities of aluminium (Al), copper (Cu), and lanthanum (La) in solution on the growth and external morphology of 3-d-old cowpea (Vigna unguiculata L.) roots for periods of up to 48 h. Root elongation rate decreased by 50% at ca. 30 μM Al, 0.3 μM Cu, or 2.0 μM La, accompanied by a decrease in the distance from the root tip to the proximal lateral root. Kinks developed in some roots 2.0 ± 0.4 mm from the root apex on exposure to Al or La (but not Cu). Light and scanning electron microscopy showed that soluble Al, Cu, or La caused similar transverse ruptures to develop > 1 mm from the root apex through the breaking and separation of the rhizodermis and outer cortex from inner-layers. The metals differed, however, in the range in concentration at which they had this effect; developing in solutions containing 54 to‑600 μM Al, but only from 0.85 to 1.8 μM Cu or 2.0 to 5.5 μM La. These findings suggest that Al, Cu, and La bind to the walls of cells, causing increased cell wall rigidity and eventual cell rupturing of the rhizodermis and outer cortex in the elongating zone. We propose that this is a major toxic effect of Al, and that Cu and La also have additional toxic effects.     

The Effect of Visual Cues on Auditory Stream Segregation in Musicians and Non-Musicians

Background

The ability to separate two interleaved melodies is an important factor in music appreciation. This ability is greatly reduced in people with hearing impairment, contributing to difficulties in music appreciation. The aim of this study was to assess whether visual cues, musical training or musical context could have an effect on this ability, and potentially improve music appreciation for the hearing impaired.

Methods

Musicians (N = 18) and non-musicians (N = 19) were asked to rate the difficulty of segregating a four-note repeating melody from interleaved random distracter notes. Visual cues were provided on half the blocks, and two musical contexts were tested, with the overlap between melody and distracter notes either gradually increasing or decreasing.

Conclusions

Visual cues, musical training, and musical context all affected the difficulty of extracting the melody from a background of interleaved random distracter notes. Visual cues were effective in reducing the difficulty of segregating the melody from distracter notes, even in individuals with no musical training. These results are consistent with theories that indicate an important role for central (top-down) processes in auditory streaming mechanisms, and suggest that visual cues may help the hearing-impaired enjoy music.     

Recovery of cowpea seedling roots from exposure to toxic concentrations of trace metals

Rhizotoxic effects of many trace metals are known, but there is little information on recovery after exposure. Roots of 3-d-old cowpea (Vigna unguiculata (L.) Walp. cv. Caloona) seedlings were grown for 4 or 12 h in solutions of 960 μM Ca and 5 μM B at two concentrations (which reduce growth by 50 or 85%) of nine trace metals that rupture the outer layers of roots. Measured concentrations were 34 or 160 μM Al, 0.6 or 1.6 μM Cu, 2.2 or 8.5 μM ?Ga, 2.3 or 12 μM Gd, 0.8 or 1.9 μM Hg, 1.0 or 26 μM In, 2.4 or 7.3 μM La, 1.8 or 3.8 μM Ru, and 1.3 or 8.6 μM Sc. Roots were rinsed, transferred to solutions free of trace metals, and regrowth monitored for up to 48 h. Recovery from exposure to Hg occurred within 4 h, but regrowth was delayed for ≥?12 h with Al, Ga, or Ru. There was poor regrowth after 4 or 12 h exposure to Cu, Gd, In, La, or Sc. Roots recovered after being grown for 12 to 48 h in 170 μM Al, 5.1 μM? Ga, 2.0 μM Hg, or 1.4 μM Ru, but the extent of recovery was reduced with longer exposure time. Microscopy showed marked differences in symptoms on roots recovering from exposure to the various trace metals. Differences in (i) concentrations that are toxic, (ii) ability of roots to recover, (iii) time for recovery to occur, and (iv) symptoms that develop, suggest that each trace metal has a unique combination of rhizotoxic effects.