Cause Of Regeneration Failure Research Articles

Defaunated and invaded insular tropical rainforests will not recover alone: Recruitment limitation factors disentangled by hierarchical models of spontaneous and assisted regeneration

Abstract Most tropical forests are now severely degraded and their ability to recover is highly dependent on frugivores which ensure seed dispersal for most woody plants. The global collapse of large vertebrates therefore raises major concerns about tropical forest succession, but few field studies have been conducted to disentangle recruitment limitations during disrupted succession. This study took place on Réunion (Mascarenes) where all large native frugivores have been extinct since human colonisation in 1665 and where multiple invasions threaten native ecosystems. We set up 20 experimental blocks on a lava flow dated back to 1800, in plant‐impoverished post‐defaunation vegetation bordered by old‐growth forests. We assessed fecundity, seed dispersal and seedling recruitment of the complete fleshy‐fruited plant community and used Bayesian analyses to disentangle the impact of multiple factors on these key processes. In the same blocks, we sowed four native trees assumed to be disperserless to test their capacity to establish, controlling for two additional post‐dispersal limitations (seed predation and competition with invasive plants). On the flow, small‐seeded native plants were fairly dispersed but did not recruit, probably due to strong competition with invasive plants; the few native species that recruited somehow were mostly medium‐seeded plants that were still dispersed; large‐seeded plants were absent from seed rain (which shows that invasive frugivores did not replace extinct ones) and subsequently from spontaneous recruitment. Instead, some alien plants, notably the tiny‐seeded highly dispersed Clidemia hirta and the medium‐seeded Psidium cattleianum largely dominated seedling recruitment. Native plants recruited better at the forest margin, including some large‐seeded species nearby mother trees. Sown large‐seeded species were able to emerge and survive in all plots whatever the treatment, which demonstrates that dispersal loss was the primary cause of regeneration failure on the flow. Synthesis. The strong modulation of the establishment capacity of native plants by seed mass shows that invasive plants win by forfeit of large‐seeded plants after native frugivores loss. Our study emphasises the fundamental role of dispersal loss and competition with invasive plants in the disruption of ecological succession, as well as the urgency of restoring seed dispersal and strengthening biosecurity regulations.

IFN-γ-STAT1-mediated CD8+ T-cell-neural stem cell cross talk controls astrogliogenesis after spinal cord injury

BackgroundSpinal cord injury (SCI) causes nearly all patients to suffer from protracted disabilities. An emerging therapeutic strategy involving the recruitment of endogenous neural stem cells (NSCs) has been developed. However, endogenous NSCs in the adult spinal cord differentiate into mostly astrocytes after traumatic injury, forming glial scars, which is a major cause of regeneration failure in SCI. Thus, understanding which factors drive the activation and differentiation of endogenous NSCs after SCI is critical for developing therapeutic drugs.MethodsThe infiltration, state, and location of CD8+ T cells in spinal cord after traumatic injury were analyzed by flow cytometry and immunofluorescence (IF) staining. The Basso Mouse Scale (BMS) scores and rotarod testing were used for motor behavioral analysis. NSCs were co-cultured with CD8+ T cells. EdU assay was used to detect proliferative cells. Western blotting was used to analyze the expression levels of STAT1, p-STAT1, and p27. ChIP-seq and ChIP-qRT-PCR analyses were used to detect the downstream of STAT1. Nestin-CreERT2::Ai9 transgenic mice were used to genetic lineage tracing of Nestin+ NSCs after SCI in vivo.ResultsA prolonged increase of activated CD8+ T cells occurs in the injured spinal cords. The behavioral analysis demonstrated that the administration of an anti-CD8 antibody promotes the recovery of locomotor function. Then, we discovered that CD8+ T cells suppressed the proliferation of NSCs and promoted the differentiation of NSCs into astrocytes by the IFN-γ-STAT1 pathway in vitro. ChIP-seq and ChIP-qRT-PCR analysis revealed that STAT1 could directly bind to the promoters of astrocyte marker genes GFAP and Aldh1l1. Genetic lineage tracing of Nestin+ NSCs demonstrated that most NSCs differentiated into astrocytes following SCI. Depleting CD8+ T cells reduced the differentiation of NSCs into astrocytes and instead promoted the differentiation of NSCs into oligodendrocytes.ConclusionIn conclusion, CD8+ T cells suppressed the proliferation of NSCs and promoted the differentiation of NSCs into astrocytes by the IFN-γ-STAT1-GFAP/Aldhl1l axis. Our study identifies INF-γ as a critical mediator of CD8+ T-cell-NSC cross talk and a potential node for therapeutic intervention in SCI.

Research progress on optic nerve injury and regeneration

<p indent="0mm">Humans have a good visual system. Retinal ganglion cells (RGCs), which connect the eyeball to the brain, fail to regenerate after injury, eventually leading to blindness. Difficulty in regeneration can be attributed in part to inhibitory molecules in glial scar and myelin and insufficient regenerative capacity intrinsic to RGCs. In addition, RGCs undergo apoptosis after optic nerve injury, which makes the regeneration of visual system more difficult. Here, we review the causes of regeneration failure and the progress achieved in repair of the visual system. Some of the encouraging findings may be applied clinically in the future to achieve meaningful regeneration of injured optic nerves.

The use of repellents to reduce predation of tree seed by wood mice (Apodemus sylvaticus L.) and grey squirrels (Sciurus carolinensis Gmelin)

The loss of tree seed through predation by granivores can be a major cause of regeneration failure in direct seeding systems. Five repellents that were of low toxicity or derived from foodstuffs were investigated for their ability to deter feeding by wood mice (Apodemus sylvaticus L.) and grey squirrels (Sciurus carolinensis Gmelin). In experiments in controlled conditions, when given the option of feeding on unlimited amounts of untreated wheat (Triticum aestivum L.), or wheat treated with aluminium ammonium sulphate, sulphonated fish oil, denatonium benzoate, ziram or capsaicin, all the repellents tested initially deterred feeding, although in one experiment mice showed some habituation to the repellents after 4 weeks. Capsaicin was the most effective treatment, and aluminium ammonium sulphate the least effective, possibly because it did not stick to the wheat grains. When ash (Fraxinus excelsior L.) seed were treated with combinations of aluminium ammonium sulphate, sulphonated fish oil or denatonium benzoate, compared to the freely available untreated seed, mice were deterred by any treatment containing aluminium ammonium sulphate, with effectiveness again declining after 4 weeks. When a mixture of broadleaved tree species were sown on farmland, coating seed with aluminium ammonium sulphate or sulphonated fish oil had no effect on seedling emergence. Capsaicin derived from chilli peppers (Capsicum sp.) showed the greatest potential as a repellent in our work, but no repellent product containing this active ingredient is currently approved for plant protection uses in the United Kingdom. Given its relatively low cost, the use of aluminium ammonium sulphate, a non-toxic repellent based on an approved food additive, which is available formulated as a registered plant protection product in the United Kingdom, may be worth considering for direct sowings where predation pressure from mice is predicted to be particularly high, or where tree species with very palatable seed are being used, to complement other predation mitigation strategies.

Changes in the stand structure (1975–2000) of coastal Banksia forest in the long absence of fire

Abstract Revisitation studies enable long‐term changes in vegetation to be deciphered and insights into plant community succession to be gained. This is particularly important when assessing the effects of fire exclusion in ecosystems where fire is thought to have once been common. Using two adjacent coastal Banksia integrifolia forest stands in southern Victoria, Australia initially surveyed in 1975 by Hazard and Parsons, we document the changes that occurred in the stand structure between 1975 and 2000. Western Park (WP) has now remained unburnt for over 100 years while Cerberus Naval Base (CNB) was most recently burnt in 1942. Banksia integrifolia densities have decreased at both sites over the 25‐years period by an average of 42–77%, as have other coastal native shrubs (e.g. Leptospermum laevigatum, Leucopogon parviflorus). Trees at WP appear to have died due to old age while mortality at CNB is presumed to be due to stand thinning in response to intense competition for light. Successful recruitment by Banksia has been minimal; trees less than 9 cm girth over bark at breast height (GBBH) were absent at CNB while no trees &lt;19 cm GBBH were observed at WP. The long‐term absence of disturbance such as fire is suspected to be one of the causes of regeneration failure of the stand at WP. Gap phase regeneration is not apparent in B. integrifolia and hence, long‐term succession to a more grassy community is likely when fire is excluded for long periods.

Population and genetic status of Primula kisoana var. kisoana, a local endemic of the northern Kanto region, Japan

Abstract Primula kisoana var. kisoana is a clonal distylous herb restricted to the Mount Narukami area of Japan. In recent years, its population has severely declined and no seed set has been observed in the natural habitat. The current status of P. k. var. kisoana was investigated to develop an effective management plan for the species. Only seven local populations, comprising less than 600 ramets, were found. The large distances between compatible pairs of genets suggest that pollen limitation may be a major cause of regeneration failure. Only 10 multilocus genotypes were found for five microsatellite loci, each of which was likely to represent a unique genet. High levels of genetic heterozygosity and no significant deviation from Hardy–Weinberg equilibrium were detected, indicating that random mating has occurred until recently. Microsatellite and chloroplast DNA polymorphism suggest that genetic differentiation has occurred between populations in different valleys. Measures to conserve the species, including the preservation of all local populations and the improvement of seed reproduction, should be applied immediately.

A novel primary culture technique for adult retina allows for evaluation of CNS axon regeneration in rodents

Unraveling the causes of regeneration failure in the adult injured CNS has remained a challenge in neurobiology. The notion that CNS neurons lose their regenerative potential during development has been challenged by the identification of several promoters of axon growth. Novel methods are required that allow to study and quantify interactions of molecular determinants, and to envisage future treatment applications. Here we report a novel, highly reproducible method for monitoring axonal regeneration of mature retinal ganglion cells (RGCs) in vitro. In contrast to earlier explantation methods, primary cultures derived from adult rodent retina are kept viable without growth factor supplements. Further, since intraretinal RGC axons remain unmyelinated, regeneration can be followed independently of non-permissive white matter compounds. Applying tracing techniques prior to retinal explantation, cell survival can be correlated to outgrowth activity on the single cell level. Following intervention with pharmacological, growth factor, or gene transfer treatments, retinal explants, and partially RGC neurites, can be processed for protein and gene expression analysis. This novel procedure will prove useful to get insight into complex cell survival and regeneration promoting cascades, and will complement in vivo strategies such as transgenic and knock out mouse models.

Windows of opportunity: white-tailed deer and the dynamics of northern hardwood forests of the northeastern US

Herbivory, lighting regimes, and site conditions are among the most important determinants of forest regeneration success, but these are affected by a host of other factors such as weather, predation, human exploitation, pathogens, wind and fire. We draw together >50 years of research on the Huntington Wildlife Forest in the central Adirondack Mountains of New York to explore regeneration of northern hardwoods. A series of studies each of which focused on a single factor failed to identify the cause of regeneration failure. However, integration of these studies led to broader understanding of the process of forest stand development and identified at least three interacting factors: lighting regime, competing vegetation and selective browsing by white-tailed deer (Odocoileus virginianus). The diverse 100–200 year-old hardwood stands present today probably reflect regeneration during periods of low deer density (<2.0 deer/km 2) and significant forest disturbance. If this hypothesis is correct, forest managers can mimic these “natural windows of opportunity” through manipulation of a few sensitive variables in the system. Further, these manipulations can be conducted on a relatively small geographic scale. Control of deer densities on a scale of 500 ha and understory American beech (Fagus grandifolia) on a scale of <100 ha in conjunction with an even-aged regeneration system consistently resulted in successful establishment of desirable hardwood regeneration.

Regeneration status of important tropical forest tree species in Bolivia: assessment and recommendations

The regeneration status of 68 of the most important tropical forest tree species in Bolivian forests was reviewed to elucidate perceived problems with natural forest regeneration and to identify potential silvicultural systems that may help establish adequate regeneration. A wide range of species, important for timber, non-timber products, and forest ecological processes, was reviewed. A combination of field research, interviews with local experts, and literature searches was used to conduct the assessment. In general, little published information was available on the regeneration ecology of Bolivian tree species. However, based on available sources, regeneration was deemed inadequate for 60% of the species reviewed. Particularly acute regeneration problems exist for the most highly valued timber species, many of which appear to need enlarged clearings and subsequent competition control for establishment. Regeneration problems were most severe for shade-intolerant and intermediate shade-tolerant hardwood species. In general, palm species had fewer regeneration problems than dicotyledonous species. Little is known about the specific mechanisms of regeneration failure for many species, but the causes of regeneration failure appear to be varied. This information indicates that solutions to regeneration problems need to be addressed on a species-by-species basis. For many high-valued shade intolerant species, however, successful regeneration may depend on the acceptance by forest industry of non-traditional forestry practices that provide for larger clearings, perhaps followed by post-harvesting silvicultural treatments to control competing vegetation.