Cell Death Symptoms Research Articles

L-histidine makes Ni2+ ‘visible’ for plant signalling systems: Shading the light on Ni2+-induced Ca2+ and redox signalling in plants.

Nickel is both an important nutrient and an ecotoxicant for plants. Organic ligands, such as L-histidine (His), play a key role in Ni2+ detoxification. Here, we show that His (added together with 0.01-10 mM Ni2+) decreases Ni2+ toxicity to Arabidopsis thaliana roots not only as a result of a decrease in Ni2+ activity, but also via the induction of signalling phenomena important for adaptation such as the generation of reactive oxygen species (ROS) and cytosolic Ca2+ transients. With the use of EPR spectroscopy, we demonstrate that Ni-His complexes generate hydroxyl radicals that is not detected by the addition of Ni2+ or His separately. Similarly, Ni-His complexes, but not Ni2+, activate Ca2+ influx and K+ efflux currents in patch-clamped root protoplasts resulting in distinct cytosolic Ca2+ signals and a transient K+ release. His prevented programmed cell death symptoms (cytoplasm shrinkage, protease and endonuclease activation) induced by Ni2+ and inhibited Ni2+ accumulation at [Ni2+]>0.3 mM. Intriguingly, priming of roots with Ni-His stimulated plant resistance to Ni2+. Overall, these data show that His triggers ROS-Ca2+-mediated reactions making Ni2+ ‘visible’ for plant signalling machinery and facilitating adaptation to the excess Ni2+.

The diagnostic journey for patients with late-onset GM2 Gangliosidoses

Late-onset forms of GM2 gangliosidosis―mainly, Tay-Sachs disease and Sandhoff disease―are under-recognized in clinical practice. In these rare lysosomal storage disorders, deficiency of β-hexosaminidase A results in excessive accumulation of GM2 ganglioside primarily within neurons, leading to cell death and progressive neurodegenerative symptoms, including ataxia, dysarthria, muscle weakness, tremors, atrophy, and psychosis. Presentation is variable and often mimics more common neurodegenerative disorders. We conducted semi-structured interviews on GM2 gangliosidoses diagnosis and treatment with five experts, 30 neurologists, and 28 patients and caregivers. Symptom onset occurred during adolescence/early adulthood in 92% of patients (median age: 14 years). Patients first visited a healthcare provider at a median age of 20 years and received a GM2 diagnosis at a median age of 26 years. Nearly all patients reported problems with their legs and balance starting from symptom onset. Problems with memory, attention span, speech and fatigue were reported more after diagnosis. Patients visited an average of eight healthcare providers before receiving a diagnosis; 64% were diagnosed by a neurologist. Four neurologists (13%) in our sample were aware that there are late-onset forms of GM2 gangliosidosis. The path to diagnosis is long for this late-onset form of a classically fatal infantile disease.

Metabolite profiling and screening of callus browning-related genes in lotus (Nelumbo nucifera).

Callus browning is a major drawback to lotus callus proliferation and regeneration. However, the underlying mechanism of its formation remains largely unknown. Herein, we aimed to explore the metabolic and molecular basis of lotus callus browning by combining histological staining, high-throughput metabolomics, and transcriptomic assays for lotus callus at three browning stages. Histological stained brown callus cross sections displayed severe cell death symptoms, accompanied by an obvious accumulation of polyphenols and lignified materials. Widely targeted metabolomics revealed extensively decreased accumulation of most detected flavonoids and benzylisoquinoline alkaloids (BIAs), as well as a few phenolic acids, amino acids and their derivatives in callus with browning symptoms. Conversely, the contents of most detected tannins were significantly increased. Subsequent comparative transcriptomics identified a set of differentially expressed genes (DEGs) associated with the biosynthesis and regulation of flavonoids and BIAs in lotus. Notably, callus browning was coupled with significantly up-regulated expression of two polyphenol oxidase (PPO) and 17 peroxidase (POD) encoding genes, while the expression of ethylene associated genes remained at marginal levels. These results suggest that lotus callus browning is primarily controlled at the level of metabolism, wherein the oxidation of flavonoids and BIAs is crucially decisive.

The Genetic Requirements for HiVir-Mediated Onion Necrosis by Pantoea ananatis, a Necrotrophic Plant Pathogen.

Pantoea ananatis is an unusual bacterial pathogen that lacks typical virulence determinants yet causes extensive necrosis in onion foliage and bulb tissues. The onion necrosis phenotype is dependent on the expression of the phosphonate toxin, pantaphos, which is synthesized by putative enzymes encoded by the HiVir (high virulence) gene cluster. The genetic contributions of individual hvr genes in HiVir-mediated onion necrosis remain largely unknown, except for the first gene, hvrA (phosphoenolpyruvate mutase, pepM), whose deletion resulted in the loss of onion pathogenicity. In this study, using gene-deletion mutation and complementation, we report that, of the ten remaining genes, hvrB to hvrF are also strictly required for the HiVir-mediated onion necrosis and in-planta bacterial growth, whereas hvrG to hvrJ partially contributed to these phenotypes. As the HiVir gene cluster is a common genetic feature shared among the onion-pathogenic P. ananatis strains that could serve as a useful diagnostic marker of onion pathogenicity, we sought to understand the genetic basis of HiVir-positive yet phenotypically deviant (non-pathogenic) strains. We identified and genetically characterized inactivating single nucleotide polymorphisms in the essential hvr genes of six phenotypically deviant P. ananatis strains. Finally, inoculation of cell-free spent medium of the isopropylthio-β-galactoside (IPTG)-inducible promoter (Ptac)-driven HiVir strain caused P.ananatis-characteristic red onion scale necrosis as well as cell death symptoms in tobacco. Co-inoculation of the spent medium with essential hvr mutant strains restored in-planta populations of the strains to the wild-type level, suggesting that necrotic tissues are important for the proliferation of P. ananatis in onion. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Overexpressing 7-Hydroxymethyl Chlorophyll a Reductase Alleviates Non-Programmed Cell Death during Dark-Induced Senescence in Intact Arabidopsis Plants.

Leaf senescence, the last stage of leaf development, is a well-regulated and complex process for investigation. For simplification, dark-induced leaf senescence has frequently been used to mimic the natural senescence of leaves because many typical senescence symptoms, such as chlorophyll (Chl) and protein degradation, also occur under darkness. In this study, we compared the phenotypes of leaf senescence that occurred when detached leaves or intact plants were incubated in darkness to induce senescence. We found that the symptoms of non-programmed cell death (non-PCD) with remaining green coloration occurred more heavily in the senescent leaves of whole plants than in the detached leaves. The pheophorbide a (Pheide a) content was also shown to be much higher in senescent leaves when whole plants were incubated in darkness by analyses of leaf Chl and its metabolic intermediates. In addition, more serious non-PCD occurred and more Pheide a accumulated in senescent leaves during dark incubation if the soil used for plant growth contained more water. Under similar conditions, the non-PCD phenotype was alleviated and the accumulation of Pheide a was reduced by overexpressing 7-hydroxymethyl Chl a (HMChl a) reductase (HCAR). Taken together, we conclude that a high soil water content induced non-PCD by decreasing HCAR activity when whole plants were incubated in darkness to induce senescence; thus, the investigation of the fundamental aspects of biochemistry and the regulation of leaf senescence are affected by using dark-induced leaf senescence.

Membrane-Bound Transcriptional Activator NTL1 from Rapeseed Positively Modulates Leaf Senescence through Targeting Genes Involved in Reactive Oxygen Species Production and Programmed Cell Death.

Leaf senescence is the last stage of leaf development and is determined by various environmental and endogenous signals. Leaf senescence can determine plant productivity and fitness. Transcription factors (TFs) with the transmembrane domain constitute a special group of regulatory proteins that can translocate from the membrane system into nuclei to exert the transcriptional function upon endogenous or exogenous stimuli. Reactive oxygen species (ROSs) play an important role in numerous processes throughout the life cycle of plants including leaf senescence. Leaf senescence is characterized by massive programmed cell death (PCD) and is a type of developmental PCD. The transcriptional regulatory relationships between membrane-bound TFs and leaf senescence remain largely uncharacterized, especially in rapeseed (Brassica napus L.), an important oil crop. Here, we show that BnaNTL1 is a membrane-bound NAC (NAM, ATAF, and CUC) TF, which is predominantly expressed in senescent leaves. Expression of BnaNTL1ΔTM, a form of BnaNTL1 devoid of the transmembrane domain, can induce serious HR-like cell death symptoms and ROS accumulation in cells. Plants overexpressing BnaNTL1ΔTM show earlier leaf senescence compared with the control, accompanied by chlorophyll degradation and electrolyte leakage. Genes involved in ROS production (RbohD), PCD (VPEs and CEP1), and leaf senescence (BFN1) are significantly induced and activated by BnaNTL1ΔTM according to the quantitative reverse transcription PCR (qRT-PCR) analysis and dual luciferase reporter (Dual-LUC) assay. Moreover, electrophoretic mobility shift assay revealed that BnaNTL1 directly bound to the NTLBS elements in promoters of RbohD, γVPE, and BFN1. In conclusion, these results demonstrate that BnaNTL1 positively modulates ROS production and HR-like cell death to induce leaf senescence.

HCAR Is a Limitation Factor for Chlorophyll Cycle and Chlorophyll b Degradation in Chlorophyll-b-Overproducing Plants.

The chlorophyll (Chl) cycle is the metabolic pathway for Chl a and Chl b inter-conversion. In this pathway, Chl b is synthesized from Chl a by the catalyzing action of chlorophyllide a oxygenase (CAO). In contrast, Chl b is firstly reduced to produce 7-hydroxymethyl Chl (HMChl) a, which is catalyzed by two isozymes of Chl b reductase (CBR), non-yellow coloring 1 (NYC1) and NYC1-like (NOL). Subsequently, HMChl a is reduced to Chl a by HMChl a reductase (HCAR). CAO plays a pivotal role in Chl a/b ratio regulation and plants over-accumulate Chl b in CAO-overexpressing plants. NYC1 is more accumulated in Chl-b-overproducing plants, while HCAR is not changed. To investigate the role of HCAR in Chl cycle regulation, the Chl metabolites of Chl-b-overproducing plants were analyzed. The results showed that HMChl a accumulated in these plants, and it decreased and the Chl a/b ratio increased by overexpressing HCAR, implying HCAR is insufficient for Chl cycle in Chl-b-overproducing plants. Furthermore, during dark-induced senescence, the non-programmed cell death symptoms (leaves dehydrated with green color retained) of Chl-b-overproducing plants were obviously alleviated, and the content of HM pheophorbide (HMPheide) a and Pheide b were sharply decreased by overexpressing HCAR. These results imply that HCAR is also insufficient for Chl degradation in Chl-b-overproducing plants during senescence, thus causing the accumulation of Chl metabolites and non-programmed cell death of leaves. With these results taken together, we conclude that HCAR is not well regulated and it is a limiting factor for Chl cycle and Chl b degradation in Chl-b-overproducing plants.

UvHrip1, an effector secreted by Ustilaginoidea virens, suppresses basal defense and promotes disease development in Arabidopsis thaliana.

Rice false smut (RFS), caused by Ustilaginoidea virens, is one of the most detrimental rice fungal diseases and pose a severe threat to rice production and quality. Effectors in U. virens often act as a set of essential virulence factors that play crucial roles in the interaction between host and the pathogen. Thus, the functions of each effector in U. virens need to be further explored. Here, a conserved small secreted hypersensitive response-inducing protein (hrip) was named UvHrip1. Functional validation was investigated to prove that UvHrip1 suppressed cell death symptom and ROS accumulation in Nicotiana benthamiana triggered by Burkholderia glumae. We performed transgenic technology to demonstrate UvHrip1 remarkably inhibited pathogen-associated molecular pattern-induced defense responses in Arabidopsis seedlings and plants, including the expression of defense-response genes. Furthermore, disease progression caused by the type III secretion system-defective mutant from Pseudomonas syringae pv. tomato DC3000 was strongly facilitated in transgenic Arabidopsis ectopic expressing UvHrip1. Our data demonstrated UvHrip1 suppresses plant innate immunity and promoting disease multiplication in Arabidopsis.

Growth inhibition and induction of programmed cell death in the root of He­lianthus annuus L. triggered by nickel ions and nickel-histidine complexes

Nickel (Ni2+) performs a number of vital functions in plants, but at high concentrations it causes toxic effects and inhibits their growth and development. The problem of nickel contamination has a special place in environmental physiology, since the refuse to use nickel alloys and therefore the reduction of Ni2+ release into the biosphere are practically impossible today. In nature one of the mechanisms of adaptation to the excessive nickel content in the medium is increased synthesis of histidine, which forms chelates with Ni2+. In the present work, for the first time, a detailed analysis of the effects of nickel and nickel-histidine complexes on the growth and development of sunflower roots (Helianthus annuus L.) of Belarusian selection (variety Orion) was carried out. It was established that Ni2+, starting from its level in the medium of 0.3 mmol/L, caused a significant growth inhibition of this agricultural plant. At a nickel concentration in the medium above 3 mmol/L, the growth of sunflower stopped completely. Histidine, introduced together with Ni2+, caused a decrease in the toxicity of this metal for the root system, in some cases shifting by single-order nickel concentrations, causing the same effect. Nickel treatment caused a significant increase in the percentage of cells with programmed cell death symptoms, while histidine inhibited the development of these symptoms. Thus, the concentration dependences of nickel and nickel-histidine complexes effects on root growth and the processes of programmed cell death in the sunflower root were first demonstrated.

ITRAQ-based quantitative proteomics reveals a ferroptosis-like programmed cell death in plants infected by a highly virulent tobacco mosaic virus mutant 24A+UPD

Plants trigger a highly orchestrated defence mechanism in response to viral infection. In this study, we aimed at understanding the molecular events that lead to more accelerated cell death in Nicotiana benthamiana plants infected with the fast-replicating TMV 24A + UPD in comparison to TMV. TMV 24A + UPD is an artificial mutant that induces more severe symptoms leading to precocious death in plants. We employed the iTRAQ-based quantitative proteomics approach to identify and map the proteomes of TMV and TMV 24A + UPD infected plants at time points that correlate with initiation of early cell death symptoms. TMV 24A + UPD proteome profile revealed 183 highly abundant proteins versus 71 for TMV infected plants. KEGG analysis revealed differentially abundant proteins in the two proteome profiles under cell death, stress signalling, protein folding, sorting, degradation, transport and catabolism. We identified unique differentially abundant proteins in the TMV 24A + UPD profile, in particular under the ferroptosis and glutathione metabolism pathways. For validation, we varied the amount of intracellular iron by supplementing plants with Fe3+, employing iron chelators and by virus induced gene silencing of iron storage protein ferritin gene. We also employed potent ferroptosis inhibitors ferostatin-1, liprostatin-1, and transiently silenced glutathione peroxidase 4 gene. TMV 24A + UPD infected plants showed accelerated cell death symptoms when intracellular iron was increased. Decreasing intracellular iron protected the plants from accelerated cell death. We also observed a decrease in TMV 24A + UPD induced cell death when we applied ferroptosis inhibitors. Glutathione peroxidase 4 gene-silenced plants showed enhanced cell death compared to non-silenced control plants. Our study uncovered a link between intracellular iron and accelerated lipid ROS-induced cell death in TMV 24A + UPD infected plants. We propose that the fast-replicating mutant of TMV induces a distinct and potent form of cell death akin to ferroptosis.

Clathrin-Mediated Endocytosis Delivers Proteolytically Active Phytaspases Into Plant Cells.

Phytaspases belong to the family of plant subtilisin-like proteases and are distinct from other family members, as they have strict and rarely occurring aspartate cleavage specificity and unusual localization dynamics. After being secreted into the apoplast of healthy plant tissues, phytaspases are able to return back into cells that have been committed to cell death due to a variety of biotic and abiotic stresses. It was recently discovered that retrograde transport of phytaspases involves clathrin-mediated endocytosis. Here, consequences of phytaspase internalization were studied. Proteolytic activity of phytaspases in the apoplast and intracellular protein fractions obtained from Nicotiana benthamiana leaves containing either endogenous phytaspase only or transiently producing Nicotiana tabacum phytaspase-EGFP protein (NtPhyt-EGFP) was determined. We demonstrated that triggering phytaspase internalization by antimycin A-induced oxidative stress is accompanied by re-distribution of phytaspase activity from the apoplast to the cell interior. Inhibition of clathrin-mediated endocytosis by co-production of the Hub protein prevented phytaspase internalization and phytaspase activity re-localization. Specificity of endocytic uptake of phytaspases was demonstrated by the co-production of an apoplast-targeted mRFP protein marker, which retained its apoplastic localization when phytaspase internalization was essentially complete. Overproduction of NtPhyt-EGFP, but not of the proteolytically inactive phytaspase mutant, per se caused moderate damage in young Nicotiana benthamiana seedlings, whereas antimycin A treatment induced a pronounced loss of cell viability independent of the NtPhyt-EGFP overproduction. Interestingly, inhibition of clathrin-mediated endocytosis abrogated cell death symptoms in both cases. In contrast to stress-induced internalization of tobacco phytaspase, Arabidopsis thaliana phytaspase-EGFP protein (AtPhyt-EGFP) was spontaneously internalized when transiently produced in N. benthamiana leaves. The AtPhyt-EGFP uptake was dependent on clathrin-mediated endocytosis as well, the internalized protein being initially visualized within the membranous vesicles. At later time points, the EGFP tag was cleaved off from AtPhyt, though the elevated level of intracellular AtPhyt proteolytic activity persisted. Our data, therefore, point to clathrin-mediated endocytosis as a means to deliver proteolytically active phytaspases into plant cells. It would be interesting to learn whether or not phytaspases are unique among the large family of plant subtilisin-like proteases in their ability to utilize retrograde trafficking.

A novel stress-responsive BnaNAL1 transcriptional activator in oilseed rape positively modulates reactive oxygen species production and cell death

Programmed cell death (PCD) is an active, genetically controlled process associated with a number of developmental processes including response/adaptation to abiotic and biotic stresses and leaf senescence. Reactive oxygen species (ROS) are important modulators of PCD and leaf senescence. However, the transcriptional control of ROS and PCD in oilseed rape (Brassica napus L.) is largely unknown. In this study, we identified a NAC transcription factor gene BnaNAL1 from oilseed rape, which encodes a transcriptional activator and plays an important role in modulating ROS and cell death. BnaNAL1 was localized exclusively to the nucleus. Expression profiling of the gene showed increased transcript levels in early senescent and mature leaves. Expression of BnaNAL1 resulted in hypersensitive response (HR)-like cell death symptoms. Further analysis of various physiological indices such as diaminobenzidine (DAB) staining, malondialdehyde contents and electrolyte leakage supported the role of BnaNAL1. Furthermore, we also observed an increase in DNA fragmentation and ROS levels. A quantitative reverse transcription PCR (qRT-PCR) analysis indicated genes involved in ROS production (RbohB), cell death (VPE1a, ZEN1), defense (PR2) and leaf senescence (HIN1, ZAT12) as putative downstream targets. We further verified that BnaNAL1 activated promoters of ZEN1, HIN1, ZAT12 and VPEs using a dual luciferase reporter assay. Using electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP)-qPCR assays, we further confirmed that BnaNAL1 could bind to the promoters of ZEN1, ZAT12, HIN1 and four VPEs for direct transcriptional modulation of these genes. Collectively our results demonstrate that BnaNAL1 positively modulates cell death and leaf senescence.

Identifying Biomarkers of Autophagy and Apoptosis in Transfected Nuclear Donor Cells and Transgenic Cloned Pig Embryos

Abstract In this study, we first investigated the effects of 3-methyladenine (3-MA), an autophagy inhibitor, and the inducer – rapamycin (RAPA) on the incidence of programmed cell death (PCD) symptoms during in vitro development of porcine somatic cell nuclear transfer (SCNT)-derived embryos. The expression of autophagy inhibitor mTOR protein was decreased in porcine SCNT blastocysts treated with 3MA. The abundance of the autophagy marker LC3 increased in blastocysts following RAPA treatment. Exposure of porcine SCNT-derived embryos to 3-MA suppressed their developmental abilities to reach the blastocyst stage. No significant difference in the expression pattern of PCD-related proteins was found between non-transfected dermal cell and transfected dermal cell groups. Additionally, the pattern of PCD in SCNT-derived blastocysts generated using SC and TSC was not significantly different, and in terms of porcine SCNT-derived embryo development rates and total blastocyst cell numbers, there was no significant difference between non-transfected cells and transfected cells. In conclusion, regulation of autophagy affected the development of porcine SCNT embryos. Regardless of the type of nuclear donor cells (transfected or non-transfected dermal cells) used for SCNT, there was no difference in the developmental potential and quantitative profiles of autophagy/apoptosis biomarkers between porcine transgenic and non-transgenic cloned embryos. These results led us to conclude that PCD is important for controlling porcine SCNT-derived embryo development, and that transfected dermal cells can be utilized as a source of nuclear donors for the production of transgenic cloned progeny in pigs.

Plant and animal PR1 family members inhibit programmed cell death and suppress bacterial pathogens in plant tissues.

A role for programmed cell death (PCD) has been established as the basis for plant-microbe interactions. A functional plant-based cDNA library screen identified possible anti-PCD genes, including one member of the PR1 family, designated P14a, from tomato. Members of the PR1 family have been subject to extensive research in view of their possible role in resistance against pathogens. The PR1 family is represented in every plant species studied to date and homologues have been found in animals, fungi and insects. However, the biological function of the PR1 protein from plants has remained elusive in spite of extensive research regarding a role in the response of plants to disease. Constitutive expression of P14a in transgenic tomato roots protected the roots against PCD triggered by Fumonisin B1, as did the human orthologue GLIPR1, indicating a kingdom crossing function for PR1. Tobacco plants transformed with a P14a-GFP fusion construct and inoculated with Pseudomonas syringae pv. tabaci revealed that the mRNA was abundant throughout the leaves, but the fusion protein was restricted to the lesion margins, where cell death and bacterial spread were arrested. Vitus vinifera grapes expressing the PR1 homologue P14a as a transgene were protected against the cell death symptoms of Pierce's disease. A pull-down assay identified putative PR1-interacting proteins, including members of the Rac1 immune complex, known to function in innate immunity in rice and animal systems. The findings herein are consistent with a role of PR1 in the suppression of cell death-dependent disease symptoms and a possible mode of action.

Novel roles of ascorbate in plants: induction of cytosolic Ca2+ signals and efflux from cells via anion channels.

Ascorbate is not often considered as a signalling molecule in plants. This study demonstrates that, in Arabidopsis roots, exogenous l-ascorbic acid triggers a transient increase of the cytosolic free calcium activity ([Ca2+]cyt.) that is central to plant signalling. Exogenous copper and iron stimulate the ascorbate-induced [Ca2+]cyt. elevation, while cation channel blockers, free radical scavengers, low extracellular [Ca2+], transition metal chelators, and removal of the cell wall inhibit this reaction. These data show that apoplastic redox-active transition metals are involved in the ascorbate-induced [Ca2+]cyt. elevation. Exogenous ascorbate also induces a moderate increase in programmed cell death symptoms in intact roots, but it does not activate Ca2+ influx currents in patch-clamped root protoplasts. Intriguingly, the replacement of gluconate with ascorbate in the patch-clamp pipette reveals a large ascorbate efflux current, which shows sensitivity to the anion channel blocker, anthracene-9-carboxylic acid (A9C), indicative of the ascorbate release via anion channels. EPR spectroscopy measurements demonstrate that salinity (NaCl) triggers the accumulation of root apoplastic ascorbyl radicals in an A9C-dependent manner, confirming that l-ascorbate leaks through anion channels under depolarization. This mechanism may underlie ascorbate release, signalling phenomena, apoplastic redox reactions, iron acquisition, and control the ionic and electrical equilibrium (together with K+ efflux via GORK channels).

α-Synuclein Trafficking in Parkinson's Disease: Insights From Fly and Mouse Models.

Protein aggregation and accumulation are common pathological hallmarks in neurodegenerative diseases. To efficiently clear and eliminate such aggregation becomes an important cellular strategy for cell survival. Lewy bodies inclusion and aggregation of α-Synuclein (α-Syn) during the pathogenesis of Parkinson’s disease (PD) serve as a good example and are potentially linked to other pathological PD features such as progressive dopaminergic neuron cell death, behavioral defects, and nonmotor symptoms like anosmia, cognitive impairment, and depression. Years of research have revealed a variety of mechanisms underlying α-Syn aggregation, clearance, and spread. Particularly, vesicular routes associated with the trafficking of α-Syn, leading to its aggregation and accumulation, have been shown to play vital roles in PD pathogenesis. How α-Syn proteins propagate among cells in a prion-like manner, either from or to neurons and glia, via means of uptake or secretion, are questions under active investigation and have been of central interest in the field of PD study. This review covers components and pathways of possible vesicular routes involved in α-Syn trafficking. Events including but not limited to exocytosis and endocytosis will be discussed within the context of an overall cellular trafficking theme. Recent advances on α-Syn trafficking mechanisms and their significance in mediating PD pathogenesis will be thoroughly reviewed, ending with a discussion on the advantages and limitations of different animal PD models.

An Arabidopsis NAC transcription factor NAC4 promotes pathogen-induced cell death under negative regulation by microRNA164.

Hypersensitive response (HR) is a form of programmed cell death (PCD) and the primary immune response that prevents pathogen invasion in plants. Here, we show that a microRNAmiR164 and its target gene NAC4 (At5g07680), encoding a NAC transcription factor, play essential roles in the regulation of HR PCD in Arabidopsis thaliana. Cell death symptoms were noticeably enhanced in NAC4-overexpressing (35S:NAC4) and mir164 mutant plants in response to avirulent bacterial pathogens. NAC4 expression was induced by pathogen infection and negatively regulated by miR164 expression. NAC4-binding DNA sequences were determined by invitro binding site selection using random oligonucleotide sequences. Microarray, chromatin immunoprecipitation and quantitative real time polymerase chain reaction (qRT-PCR) analyses, followed by cell death assays in protoplasts, led to the identification of NAC4 target genes LURP1, WRKY40 and WRKY54, which act as negative regulators of cell death. Our results suggest that NAC4 promotes hypersensitive cell death by suppressing its target genes and this immune process is fine-tuned by the negative action of miR164.

Two familial ALS proteins function in prevention/repair of transcription-associated DNA damage

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron dysfunction disease that leads to paralysis and death. There is currently no established molecular pathogenesis pathway. Multiple proteins involved in RNA processing are linked to ALS, including FUS and TDP43, and we propose a disease mechanism in which loss of function of at least one of these proteins leads to an accumulation of transcription-associated DNA damage contributing to motor neuron cell death and progressive neurological symptoms. In support of this hypothesis, we find that FUS or TDP43 depletion leads to increased sensitivity to a transcription-arresting agent due to increased DNA damage. Thus, these proteins normally contribute to the prevention or repair of transcription-associated DNA damage. In addition, both FUS and TDP43 colocalize with active RNA polymerase II at sites of DNA damage along with the DNA damage repair protein, BRCA1, and FUS and TDP43 participate in the prevention or repair of R loop-associated DNA damage, a manifestation of aberrant transcription and/or RNA processing. Gaining a better understanding of the role(s) that FUS and TDP43 play in transcription-associated DNA damage could shed light on the mechanisms underlying ALS pathogenesis.

Cylindrospermopsin induces biochemical changes leading to programmed cell death in plants.

In the present study we provide cytological and biochemical evidence that the cyanotoxin cylindrospermopsin (CYN) induces programmed cell death (PCD) symptoms in two model vascular plants: the dicot white mustard (Sinapis alba) and the monocot common reed (Phragmites australis). Cytological data include chromatin fragmentation and the increase of the ratio of TUNEL-positive cells in roots, the latter being detected in both model systems studied. The strongest biochemical evidence is the elevation of the activity of several single-stranded DNA preferring nucleases-among them enzymes active at both acidic and alkaline conditions and are probably directly related to DNA breaks occurring at the initial stages of plant PCD: 80kDa nucleases and a 26kDa nuclease, both having dual (single- and double-stranded nucleic acid) specificity. Moreover, the total protease activity and in particular, a 53-56kDa alkaline protease activity increases. This protease could be inhibited by PMSF, thus regarded as serine protease. Serine proteases are detected in all organs of Brassicaceae (Arabidopsis) having importance in differentiation of specialized plant tissue through PCD, in protein degradation/processing during early germination and defense mechanisms induced by a variety of biotic and abiotic stresses. However, knowledge of the physiological roles of these proteases and nucleases in PCD still needs further research. It is concluded that CYN treatment induces chromatin fragmentation and PCD in plant cells by activating specific nucleases and proteases. CYN is proposed to be a suitable molecule to study the mechanism of plant apoptosis.

Symptom heterogeneity in Huntington's disease correlates with neuronal degeneration in the cerebral cortex

BackgroundHuntington's disease (HD) is characterised by variable symptoms and neuropathology of the basal ganglia and cortex. Previously, we have shown that the pattern of pyramidal cell loss in 8 different cortical regions correlates with the phenotypic variability in HD. In the primary motor and anterior cingulate cortices, the pattern of interneuron degeneration correlates with pyramidal cell death and variable HD symptom profiles. ObjectivesThis study aimed to examine the pattern of interneuron degeneration in 3 further regions of the HD cortex (primary sensory, superior frontal, superior parietal cortices) to determine whether HD neuropathogenesis was characterised by a general fundamental pattern of cortical interneuron loss, and explore the relationship between cortical interneuron loss with previously determined pyramidal cell loss and clinical heterogeneity. MethodsStereological counting was used to quantify 3 sub-populations of calcium-binding protein containing interneurons in 3 cortical human brain regions of 14 HD and 13 control cases as used in our previous studies (Nana et al., 2014; Kim et al., 2014). The HD cases were grouped according to their predominant symptom profile (“motor”, “mood”, “mixed”). ResultsThe present results demonstrated a heterogeneous loss of interneurons across the 3 cortical regions which, when compared with our previous studies, mirrored the pattern of pyramidal cell loss in the same cortical areas. Most interestingly, the pattern of neuronal loss in these regions correlated with the variable HD symptom profiles. ConclusionThe overall findings in our present and previous cortical studies establish a clear correlative pattern of variable cortical neuronal degeneration in HD pathogenesis, which mirrors the heterogeneity of HD symptom phenotypes.