The concept of plant defense using toxic mineral elements originated as an explanation for extremely elevated concentrations of some elements (termed hyperaccumulation) in some plant tissues. The ...Defensive Enhancement Hypothesis suggests that hyperaccumulation evolved because, after an initial defensive benefit accrued from a relatively low initial concentration, increased concentration of an element provided increased plant fitness and drove evolution of higher element concentrations until hyperaccumulation was achieved. The Joint Effects Hypothesis postulates that additive or synergistic effects between element-based defenses, or between toxic element and organic chemical defenses, may have contributed to the evolution of hyperaccumulation. By lessening the concentration of an element necessary to provide an initial defensive benefit to a plant, joint effects could decrease the level of an element that provides an initial defensive benefit, allowing additive or synergistic defensive enhancement to take effect. Recent experimental tests have demonstrated defense at relatively low element concentrations, and tests of metal/metal and metal/organic compound combinations have shown joint effects. These hypotheses suggest how hyperaccumulator plants may have evolved in response to plant–herbivore interactions, and suggest that toxic element levels below those used to define hyperaccumulation may be ecologically effective.
Heavy metals are an important class of pollutants with both lethal and sublethal effects on organisms. The latter are receiving increased attention, as these may have harmful ecological outcomes. For ...example, recent explorations of heavy metals in freshwater habitats reveal that they can modify chemical communication between individuals, resulting in “info-disruption” that can impact ecological relationships within and between species. Info-disruption can affect animal behavior and social structure, which in turn can modify both intraspecies and interspecies interactions. In terrestrial habitats, info-disruption by metals is not well studied, but recent demonstrations of chemical signaling between plants via both roots and volatile organic molecules provide potential opportunities for info-disruption. Metals in terrestrial habitats also can form elemental plant defenses, in which they can defend a plant against natural enemies. For example, hyperaccumulation of metals by terrestrial plants has been shown to provide defensive benefits, although in almost all known cases the metals are not anthropogenic pollutants but are naturally present in soils inhabited by these plants. Info-disruption among microbes is another arena in which metal pollutants may have ecological effects, as recent discoveries regarding quorum sensing in bacteria provide an avenue for metals to affect interactions among bacteria or between bacteria and other organisms. Metal pollutants also may influence immune responses of organisms, and thus affect pathogen/host relationships. Immunomodulation (modification of immune system function) has been tied to some metal pollutants, although specific metals may boost or reduce immune system function depending on dose. Finally, the study of metal pollutants is complicated by their frequent occurrence as mixtures, either with other metals or with organic pollutants. Most studies of metal pollutants focus on single metals and therefore oversimplify complex field conditions. Study of pollutant impacts on chemical ecology also are difficult due to the necessity of studying effects at varying ecological scales: “dynamic scaling” of chemical ecology studies is rarely done completely. It is clear that much remains to be learned about how heavy metal pollution impacts organisms, and that exciting new research frontiers are available for experimental exploration.
Heavy metals are released into the environment by both anthropogenic and natural sources. Highly reactive and often toxic at low concentrations, they may enter soils and groundwater, bioaccumulate in ...food webs, and adversely affect biota. Heavy metals also may remain in the environment for years, posing long-term risks to life well after point sources of heavy metal pollution have been removed. In this review, we compile studies of the community-level effects of heavy metal pollution, including heavy metal transfer from soils to plants, microbes, invertebrates, and to both small and large mammals (including humans). Many factors contribute to heavy metal accumulation in animals including behavior, physiology, and diet. Biotic effects of heavy metals are often quite different for essential and non-essential heavy metals, and vary depending on the specific metal involved. They also differ for adapted organisms, including metallophyte plants and heavy metal-tolerant insects, which occur in naturally high-metal habitats (such as serpentine soils) and have adaptations that allow them to tolerate exposure to relatively high concentrations of some heavy metals. Some metallophyte plants are hyperaccumulators of certain heavy metals and new technologies using them to clean metal-contaminated soil (phytoextraction) may offer economically attractive solutions to some metal pollution challenges. These new technologies provide incentive to catalog and protect the unique biodiversity of habitats that have naturally high levels of heavy metals.
Elemental hyperaccumulation may have several functions, including plant defense against natural enemies. A total of 34 studies, including 72 experimental tests, have been conducted to date. At least ...some tests have demonstrated defense by hyperaccumulated As, Cd, Ni, Se and Zn, but relatively few plant taxa and natural enemies have been investigated. Defense by hyperaccumulated Ni has been shown for most leaf/root chewing herbivores and pathogens tested (20 of 26 tests) but not for herbivores of other feeding modes (1 of 8 tests). Most tests (5 of 6) using Ni concentrations below accumulator levels found no defensive effect, and the single test using plants in the accumulator range also found no effect. For Zn, mixed results have been reported for both hyperaccumulator (3 of 6 tests showed defense) and accumulator levels (3 of 4 tests showed defense). These tests have focused exclusively on leaf chewing/scraping herbivores: no herbivores of other feeding modes, or pathogens, have been tested. Both hyperaccumulator and accumulator concentrations of Se generally have shown defensive effects (12 of 14 tests). Most (75%) of these positive results used plants with accumulator Se concentrations. The three tests of Cd showed defensive effects in two cases, one for hyperaccumulator and one for sub-accumulator Cd concentrations. Arsenic has been tested only once, and was found effective against a leaf-chewing herbivore at a concentration much less than the hyperaccumulator level. Defense studies have used a variety of experimental approaches, including choice and no-choice experiments as well as experiments that use artificial diet or growth media. Investigations of hyperaccumulation as a defense against natural enemies have led to two emerging questions. First, what is the minimum concentration of an element sufficient for defense? Evidence suggests that plants other than hyperaccumulators (such as accumulators) may be defended by elements against some natural enemies. Second, do the effects of an element combine with the effects of organic defensive compounds in plants to produce enhanced joint defensive effects? Recent investigation of this “joint effects hypothesis,” using Ni and secondary plant compounds in artificial insect diet, has demonstrated joint effects. Initial answers to both these questions suggest that defensive effects of elements in plants are more widespread than previously believed. These results also suggest an evolutionary pathway by which elemental hyperaccumulation may have evolved from accumulation. In this “defensive enhancement” scenario, defensive benefits of elevated levels of elements may have led to stepwise increases in element concentrations that further magnified these benefits. This series of steps could have led to increased accumulation, and ultimately hyperaccumulation, of elements by plants.
Formation of the death-inducing signaling complex (DISC) is a critical step in death receptor-mediated apoptosis, yet the mechanisms underlying assembly of this key multiprotein complex remain ...unclear. Using quantitative mass spectrometry, we have delineated the stoichiometry of the native TRAIL DISC. While current models suggest that core DISC components are present at a ratio of 1:1, our data indicate that FADD is substoichiometric relative to TRAIL-Rs or DED-only proteins; strikingly, there is up to 9-fold more caspase-8 than FADD in the DISC. Using structural modeling, we propose an alternative DISC model in which procaspase-8 molecules interact sequentially, via their DED domains, to form a caspase-activating chain. Mutating key interacting residues in procaspase-8 DED2 abrogates DED chain formation in cells and disrupts TRAIL/CD95 DISC-mediated procaspase-8 activation in a functional DISC reconstitution model. This provides direct experimental evidence for a DISC model in which DED chain assembly drives caspase-8 dimerization/activation, thereby triggering cell death.
Display omitted
► The TRAIL DISC is a soluble >700 kDa complex of TRAIL-Rs, FADD, and DED-only proteins ► LC-MS/MS defines FADD as substoichiometric relative to TRAIL-Rs/DED-only proteins ► Structural modeling reveals that FADD recruits multiple DED-only proteins to the DISC ► We uncover a crucial role for caspase-8 DED chain assembly in triggering cell death
Aim
The study aimed to investigate the effectiveness of a web‐based therapy programme, ‘Move it to improve it’ (Mitii™), in children with unilateral cerebral palsy (UCP) on occupational performance, ...upper limb function, and visual perception.
Method
Participants (n=102) were matched in pairs and randomized to intervention (Mitii for 20wks; 26 males, mean age 11y 8mo 2y 4mo, Manual Ability Classification System level I=11, II=39, III=1) or control (standard care; 25 males, mean age 11y 10mo 2y 5mo, Manual Ability Classification System level I=13, II=37). Outcomes were the Assessment of Motor and Process Skills (AMPS), Assisting Hand Assessment, Jebsen–Taylor Test of Hand Function (JTTHF), Melbourne Assessment of Unilateral Upper Limb Function (MUUL), Canadian Occupational Performance Measure (COPM), and Test of Visual Perceptual Skills (TVPS‐3).
Results
Participants completed on average 32.4 hours of Mitii (range 3.7–74.7h). The Mitii group demonstrated significantly greater post‐intervention scores than the comparison group on the AMPS, JTTHF dominant upper limb, COPM, and TVPS‐3. The differences between groups were not clinically significant. There were no differences between groups on measures of impaired upper limb function.
Interpretation
Mitii delivers individualized, web‐based therapy at home and has potential to increase therapy dose. Mitii can be considered as an option to enhance occupational performance and visual perception for children with UCP.
What this study adds
First adequately powered study of interactive computer play for unilateral cerebral palsy (UCP).
‘Move it to improve it’ (Mitii) can enhance activities of daily living (ADL), perceived, occupational performance and visual perception.
Mitii had no significant effect on impaired upper limb function.
This article is commented on by Karlsson on page 497 of this issue.
Forage fish play a pivotal role in marine ecosystems and economies worldwide by sustaining many predators and fisheries directly and indirectly. We estimate global forage fish contributions to marine ...ecosystems through a synthesis of 72 published Ecopath models from around the world. Three distinct contributions of forage fish were examined: (i) the ecological support service of forage fish to predators in marine ecosystems, (ii) the total catch and value of forage fisheries and (iii) the support service of forage fish to the catch and value of other commercially targeted predators. Forage fish use and value varied and exhibited patterns across latitudes and ecosystem types. Forage fish supported many kinds of predators, including fish, seabirds, marine mammals and squid. Overall, forage fish contribute a total of about $16.9 billion USD to global fisheries values annually, i.e. 20% of the global ex‐vessel catch values of all marine fisheries combined. While the global catch value of forage fisheries was $5.6 billion, fisheries supported by forage fish were more than twice as valuable ($11.3 billion). These estimates provide important information for evaluating the trade‐offs of various uses of forage fish across ecosystem types, latitudes and globally. We did not estimate a monetary value for supportive contributions of forage fish to recreational fisheries or to uses unrelated to fisheries, and thus the estimates of economic value reported herein understate the global value of forage fishes.
Vaccination and infection promote the formation, tissue distribution, and clonal evolution of B cells, which encode humoral immune memory. We evaluated pediatric and adult blood and deceased adult ...organ donor tissues to determine convergent antigen-specific antibody genes of similar sequences shared between individuals. B cell memory varied for different pathogens. Polysaccharide antigen-specific clones were not exclusive to the spleen. Adults had higher clone frequencies and greater class switching in lymphoid tissues than blood, while pediatric blood had abundant class-switched convergent clones. Consistent with reported serology, prepandemic children had class-switched convergent clones to severe acute respiratory syndrome coronavirus 2 with weak cross-reactivity to other coronaviruses, while adult blood or tissues showed few such clones. These results highlight the prominence of early childhood B cell clonal expansions and cross-reactivity for future responses to novel pathogens.
Root foraging may allow hyperaccumulator plants to enhance element accumulation. This study compared root proliferation of two annual serpentine endemics: Streptanthus polygaloides (Ni ...hyperaccumulator) and Streptanthus insignis (nonhyperaccumulator). In a greenhouse experiment, pots were divided by a sealed partition, Ni‐amended soil (800 mg kg −1) in one half, unamended soil in the other. Seeds were germinated over the partition, allowing roots to explore both soils. After 5 months, roots from each side of each pot were harvested, washed, dried, and weighed. Streptanthus polygaloides root biomass was significantly (twofold) greater in Ni‐amended soil whereas S. insignis root biomass was similar in the two soils. In a lab experiment, seedlings were grown in vertical agar‐filled petri dishes to determine if Ni affected seedling root growth. Seedlings were placed on either side of a central filter paper strip soaked in either NiCl2 solution or deionized water. Growth direction of the primary root (toward, away, neutral) and lateral root numbers and lengths were recorded. For seedlings, primary root direction and lateral root numbers/lengths were significantly increased toward Ni‐soaked filter paper only for S. polygaloides. We conclude that S. polygaloides exhibited positive root foraging responses. These may enhance Ni uptake and we suggest the term “nickelophilic root foraging” be applied to this behavior.
In this study, we compared root proliferation of two annual serpentine endemics: Streptanthus polygaloides (Ni hyperaccumulator) and Streptanthus insignis (nonhyperaccumulator). Our results showed that S. polygaloides exhibited a root growth response toward elevated soil Ni concentrations in both a split‐pot greenhouse study and a petri dish lab experiment, whereas S. insignis did not show any directional growth.
PDF
