Alpine cushion plants inhibit the loss of phylogenetic diversity in severe environments

Biotic interactions can shape phylogenetic community structure (PCS). However, we do not know how the asymmetric effects of foundation species on communities extend to effects on PCS. We assessed PCS of alpine plant communities around the world, both within cushion plant foundation species and adjacent open ground, and compared the effects of foundation species and climate on alpha (within‐microsite), beta (between open and cushion) and gamma (open and cushion combined) PCS. In the open, alpha PCS shifted from highly related to distantly related with increasing potential productivity. However, we found no relationship between gamma PCS and climate, due to divergence in phylogenetic composition between cushion and open sub‐communities in severe environments, as demonstrated by increasing phylo‐beta diversity. Thus, foundation species functioned as micro‐refugia by facilitating less stress‐tolerant lineages in severe environments, erasing a global productivity – phylogenetic diversity relationship that would go undetected without accounting for this important biotic interaction.     

A comparative ethnobotany of Khevsureti,Samtskhe-Javakheti,Tusheti, Svaneti,and Racha-Lechkhumi,Republic of Georgia (Sakartvelo), Caucasus

Background

The Republic of Georgia (Sakartvelo in Georgian language) is part of the Caucasus biodiversity hotspot, and human agricultural plant use dates bat at least 6000 years. However, little ethnobiological research has been published from the region since the 1940s. Given the lack of recent research in the region, the present study we report on plant uses in Skartvelo (Republic of Georgia), Caucasus. We hypothesized that, (1) given the long tradition of plant use, and the isolation under Soviet rule, plant use both based on homegardens and wild harvesting would be more pronounced in Georgia than in the wiser region, (2) the Soviet occupation would have had broad influence on plant use, and (3) there would still be incidence of knowledge loss despite wide plant use.

Methods

Fieldwork was conducted in Khevsureti, Samtskhe-Javakheti, Tusheti, Svaneti, and Racha in July–August 2013, July–August 2014, and September–October 2015. Interviews using semi-structured questionnaires were conducted with 170 participants (80 women and 90 men) after obtaining their oral prior informed consent. All interviews were carried out in the participants’ homes and gardens by native speakers of Georgian and its local dialects (Svan, Tush, Khevsur, Psav), or, where participants spoke these as their native language, Armenian, Russian, or Greek.

Results

In the present study we encountered 480 plant species belonging to 249 genera of 95 families being used in the research region. The highest number of species and of unique species were reported from the remote Tusheti-Khevsureti region. Informant consensus and number of use reports were highest for each region in the food and medicinal use categories. Of the 480 plants being used in the research region 282 species were exclusively wild-harvested, 103 were grown in homegardens, and 84 were both grown in gardens and sourced in the wild.

Conclusions

Plant species, and uses, found in our study, both for Georgia in general, as well as for its regions, showed clear relations to the wider Caucasus - Asia Minor - Balkans cultural complex. However, plant use in Georgia was much more diverse than reported in other studies from Eurasia.

     

Who Needs Microtubules? Myogenic Reorganization of MTOC,Golgi Complex and ER Exit Sites Persists Despite Lack of Normal Microtubule Tracks

A wave of structural reorganization involving centrosomes, microtubules, Golgi complex and ER exit sites takes place early during skeletal muscle differentiation and completely remodels the secretory pathway. The mechanism of these changes and their functional implications are still poorly understood, in large part because all changes occur seemingly simultaneously. In an effort to uncouple the reorganizations, we have used taxol, nocodazole, and the specific GSK3-β inhibitor DW12, to disrupt the dynamic microtubule network of differentiating cultures of the mouse skeletal muscle cell line C2. Despite strong effects on microtubules, cell shape and cell fusion, none of the treatments prevented early differentiation. Redistribution of centrosomal proteins, conditional on differentiation, was in fact increased by taxol and nocodazole and normal in DW12. Redistributions of Golgi complex and ER exit sites were incomplete but remained tightly linked under all circumstances, and conditional on centrosomal reorganization. We were therefore able to uncouple microtubule reorganization from the other events and to determine that centrosomal proteins lead the reorganization hierarchy. In addition, we have gained new insight into structural and functional aspects of the reorganization of microtubule nucleation during myogenesis.     

Autophagy and lysosomes in Pompe disease

In Pompe disease, a deficiency of lysosomal acid alpha-glucosidase, intralysosomal glycogen accumulates in multiple tissues, with skeletal and cardiac muscle most severely affected.(1) Complete enzyme deficiency results in rapidly progressive infantile cardiomyopathy and skeletal muscle myopathy that is fatal within the first two years of life. Patients with partial enzyme deficiency suffer from skeletal muscle myopathy and experience shortened lifespan due to respiratory failure. The major advance has been the development of enzyme replacement therapy, which recently became available for Pompe patients. However, the effective clearance of skeletal muscle glycogen, as shown by both clinical and preclinical studies, has proven more difficult than anticipated.(2-4) Our recent work published in Annals of Neurology(5) was designed to cast light on the problem, and was an attempt to look beyond the lysosomes by analyzing the downstream events affected by the accumulation of undigested substrate in lysosomes. We have found that the cellular pathology in Pompe disease spreads to affect both endocytic (the route of the therapeutic enzyme) and autophagic (the route of glycogen) pathways, leading to excessive autophagic buildup in therapy-resistant skeletal muscle fibers of the knockout mice.     

Neuronal replacement from endogenous precursors in the adult brain after stroke

In the adult brain, new neurons are continuously generated in the subventricular zone and dentate gyrus, but it is unknown whether these neurons can replace those lost following damage or disease. Here we show that stroke, caused by transient middle cerebral artery occlusion in adult rats, leads to a marked increase of cell proliferation in the subventricular zone. Stroke-generated new neurons, as well as neuroblasts probably already formed before the insult, migrate into the severely damaged area of the striatum, where they express markers of developing and mature, striatal medium-sized spiny neurons. Thus, stroke induces differentiation of new neurons into the phenotype of most of the neurons destroyed by the ischemic lesion. Here we show that the adult brain has the capacity for self-repair after insults causing extensive neuronal death. If the new neurons are functional and their formation can be stimulated, a novel therapeutic strategy might be developed for stroke in humans.     

Environment matters: synaptic properties of neurons born in the epileptic adult brain develop to reduce excitability

Neural progenitors in the adult dentate gyrus continuously produce new functional granule cells. Here we used whole-cell patch-clamp recordings to explore whether a pathological environment influences synaptic properties of new granule cells labeled with a GFP-retroviral vector. Rats were exposed to a physiological stimulus, i.e., running, or a brain insult, i.e., status epilepticus, which gave rise to neuronal death, inflammation, and chronic seizures. Granule cells formed after these stimuli exhibited similar intrinsic membrane properties. However, the new neurons born into the pathological environment differed with respect to synaptic drive and short-term plasticity of both excitatory and inhibitory afferents. The new granule cells formed in the epileptic brain exhibited functional connectivity consistent with reduced excitability. We demonstrate a high degree of plasticity in synaptic inputs to adult-born new neurons, which could act to mitigate pathological brain function.     

2,4-Dichlorophenoxyacetic Acid and Related Chlorinated Compounds Inhibit Two Auxin-Regulated Type-III Tobacco Glutathione S-Transferases

Two auxin-inducible glutathione S-transferase (GST, EC 2.5.1.18) isozymes from tobacco (Nicotiana tabacum, White Burley) were partially characterized. GST1-1 and GST2-1 are members of a recently identified new type of plant GST isozymes that we will here refer to as type III. Both enzymes were active, with 1-chloro-2,4-dinitrobenzene as a substrate, when expressed in bacteria as fusion proteins. The apparent Km for 1-chloro-2,4-dinitrobenzene was found to be 0.85 [plus or minus] 0.25 mM for GST1-1 and 0.20 [plus or minus] 0.15 mM for GST2-1. The apparent Km for glutathione was similar for both enzymes, 0.40 [plus or minus] 0.15 mM. The in vitro activity of both enzymes could be inhibited by the synthetic auxin 2,4-dichlorophenoxyacetic acid, with an apparent Ki of 80 [plus or minus] 40 [mu]M for GST1-1 and 200 [plus or minus] 100 [mu]M for GST2-1. The GST1-1 was also inhibited by structurally related substances, such as 2,4-dichlorobenzoic acid, with a roughly similar Ki. The nonchlorinated structures benzoic acid and phenoxyacetic acid did not inhibit. p-Chloroisobutyric acid, or clofibric acid, an auxin-transport inhibitor, was found to be an active inhibitor as well. The strongest inhibitor identified, however, was a phenylacetic acid derivative, ethacrynic acid, which showed an apparent Ki of 5 [plus or minus] 5 [mu]M for both enzymes. This substance is a known inducer as well as a substrate of specific mammalian GSTs. The results presented here indicate that the type III plant GSTs might be involved in the metabolism or transport of chlorinated substances that are structurally related to auxins. The possibility that auxins are endogenous ligands or substrates for GSTs is discussed.     

Promoter analysis of the auxin-regulated tobacco glutathione S-transferase genes Nt103-1 and Nt103-35

We have analysed the promoter regions of two closely related auxin-regulated glutathione S-transferase genes. All active deletion constructs tested showed expression of the reporter gene -glucuronidase (gusA) in root tips of young seedlings and newly developing lateral roots. Auxin treatment greatly enhanced the level of expression. The Nt103-1 promoter region –370/–276 was found to be necessary, at least as a quantitative element to confer auxin-responsiveness to a reporter gene, and sequences responsible for the auxin-responsiveness must be located downstream of –370. The region –651/–370 contains sequence information necessary for uninduced expression. The Nt103-35 promoter manifested its auxin-responsiveness within the –504/–310 region. Electrophoretic mobility shift analysis, using nuclear extracts from tobacco leaves and suspension cells, identified a factor binding to a sequence (ap103, TGAGTCT) at position –560 of the Nt103-1 promoter, which shows homology to the mammalian AP-1 site. A second factor was found to bind a sequence (as103, ATAGCTAAGTGCTTACG) with homology to the CaMV 35S promoter as-1 element. The as103 element is present in both promoters and positioned around –360, so within the region determined to be indispensable for the response to auxin. A third factor was found binding to the –276/–190 region of both promoters. Combined, these data point to the relevance of a 90 bp region for auxin-induced activity of both tobacco genes. The ASF-1 like factor binding to the as103 element within this region might be involved in mediating the auxin response.