Regulation of mitochondrial NAD pool via NAD+ transporter 2 is essential for matrix NADH homeostasis and ROS production in Arabidopsis

Reactive oxygen species(ROS) play a crucial role in numerous biological processes in plants, including development, responses to environmental stimuli, and programmed cell death(PCD). Deficiency in MOSAIC DEATH 1(MOD1), a plastid-localized enoyl-ACP reductase essential for de novo fatty acid biosynthesis in Arabidopsis thaliana, leads to the increased malate export from chloroplasts to mitochondria, and the subsequent accumulation of mitochondria-generated ROS and PCD. In this study, we report the identification and characterization of a mod1 suppressor, som592. SOM592 encodes mitochondrion-localized NAD~+ transporter 2(NDT2). We show that the mitochondrial NAD pool is elevated in the mod1 mutant. The som592 mutation fully suppressed mitochondrial NADH hyper-accumulation, ROS production, and PCD in the mod1 mutant, indicating a causal relationship between mitochondrial NAD accumulation and ROS/PCD phenotypes. We also show that in wild-type plants, the mitochondrial NAD+uptake is involved in the regulation of ROS production in response to continuous photoperiod. Elevation of the alternative respiration pathway can suppress ROS accumulation and PCD in mod1, but leads to growth restriction. These findings uncover a regulatory mechanism for mitochondrial ROS production via NADH homeostasis in Arabidopsis thaliana that is likely important for growth regulation in response to altered photoperiod.     

Proteomic Analysis of Horseweed (Conyza canadensis) Subjected to Caprylic Acid Stress

Caprylic acid (CAP) is anticipated to be a potential biocontrol herbicide in the control of weeds, however the molecular mechanism of how CAP affects weeds is poorly understood. Here, the physiological and biochemical (protein‐level) changes in horseweed (Conyza canadensis L.) are studied under CAP treatment, with infrared gas analyzer and label‐free quantitative proteomics methods. In total, 112 differentially‐accumulated proteins (DAPs) (>1.5 fold change, p < 0.05) are present between treated horseweed and control samples, with 46 up‐regulated and 66 down‐regulated proteins. These DAPs are involved in 28 biochemical pathways, including photosynthesis pathways. In particular, six photosynthesis proteins show significant abundance changes in the CAP‐treated horseweed. The qRT‐PCR results confirm three of the six genes involved in photosynthesis. Moreover, by measuring photosynthesis characteristics, CAP was shown to decrease photosynthetic rate, stomatal conductance, intercellular CO₂ concentration, and the transpiration rate of horseweed. These results suggest that photosystem I is one of the main biological processes involved in the response of horseweed to CAP.     

Organelle aging:Lessons from model organisms

Most cellular processes descend into failure during aging. While a large collection of longevity pathways has been identified in the past decades, the mechanism for age-related decline of cellular homeostasis and organelle function remains largely unsolved. It is known that many organelles undergo structural and functional changes during normal aging, which significantly contributes to the decline of tissue function at old ages. Since recent studies have revealed an emerging role of organelles as regulatory hubs in maintaining cellular homeostasis, understanding of organelle aging will provide important insights into the cellular basis of organismal aging. Here we review current progress on the characterization of age-dependent structural and functional alterations in the more well-studied organelles, as well as the known mechanisms governing organelle aging in model organisms, with a special focus on the fruit fly Drosophila melanogaster.     

High-Efficiency Rescue of Equine Infectious Anemia Virus from a CMV-Driven Infectious Clone

<正>Dear Editor,Equine infectious anemia virus (EIAV) belongs to the macrophage-tropic lentiviruses family and infects mainly equines, including horses, donkeys and mules. EIAV shares many similar characteristics in its viral biology and hostvirus immune regulation with other lentiviruses, such as human immunodeficiency virus type 1 (HIV-1) and simian immunodeficiency virus (SIV), and has been accepted as a     

Different carbonic supplements induced changes of microflora in two types of compost teas and biocontrol efficiency against Pythium aphanidermatum

ABSTRACT

Considering the different carbonic source utilisation abilities of microbial species, we used six carbonic supplements to acclimate the microorganisms in two types of compost teas (named CT1 and CT2). The effects of the different carbonic supplements on the physicochemical and biological parameters of the acclimated microbial broth were investigated. The influence of these supplements on the biocontrol effect of the broth against cucumber damping off caused by Pythium aphanidermatum was also assessed. Results showed that treatment with glucose, sucrose, or starch reduced the pH and weakened the biocontrol effect of the acclimated microbial broth. The glucose treatment increased the population size of fungi and yeast. The chitin, cellulose, and wheat straw treatments significantly elevated the pH and electrical conductivity (P?<?0.05), increased the bacterial population size, and positively affected the biocontrol effect of the acclimated microbial broth. The glucose treatment had higher (75.3% and 79.4% for the CT1 and CT2, respectively) whereas the wheat straw treatment had lower (34.6% and 25.6% for the CT1 and CT2, respectively) disease incidence relative to the blank control (85.6%), bacterial population size (r?=?0.64 and 0.69) and number of colony types (r?=?0.82 and 0.76) highly correlated with the biocontrol effect of CT1 and CT2 while the reducing sugar content negatively correlated with the biocontrol effect (r?=??0.57 and ?0.86).     

Lipidomics characterization of the alterations of Trichoderma brevicompactum membrane glycerophospholipids during the fermentation phase

Journal of Industrial Microbiology & Biotechnology - The biological membrane lipid composition has been demonstrated to greatly influence the secretion of secondary metabolites. This study was...     

Fullerene nanoparticles for the treatment of ulcerative colitis

Ulcerative colitis (UC) is a long-term, recurrent inflammatory bowel disease for which no effective cure is yet available in the clinical setting. Repairing the barrier dysfunction of the colon and reducing intestinal inflammation are considered key objectives to cure UC. Here we demonstrate a novel therapeutic strategy based on a C₆₀ fullerene suspension (C₆₀FS) to treat dinitrobenzene sulfonic acid-induced UC in an animal model. C₆₀FS can repair the barrier dysfunction of UC and effectively promote the healing of ulcers; it also manifests better treatment effects compared with mesalazine enema. C₆₀FS can reduce the numbers of basophils in the blood of UC rats and mast cells in the colorectal tissue, thereby effectively alleviating inflammation. The expression of H1R, H4R, and VEGFR2 receptors in colorectal tissues is inhibited by C₆₀FS, and the levels of histamine and prostaglandin in the rat blood are reduced. This work presents a reliable strategy based on fullerene to cure UC and provides a novel guide for UC treatment.

     

D-Serine inhibits AMPA receptor-mediated current in rat hippocampal neurons

D-Serine, a recently identified gliotransmitter, serves as an endogenous coagonist binding to the glycine site of N-methyl-D-aspartate (NMDA) receptors. However, it is not clear whether this native ligand is able to bind to and modulate alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) receptors. In the present study, we showed that D-serine was able to concentration-dependently inhibit kainate-induced AMPA receptor-mediated current in acutely isolated hippocampal neurons. The blocking action of D-serine on AMPA receptors was characterized by a shift in concentration-response curve of kainate-induced current to the right with no change in the maximal response and independent of holding potential in the range of -80 to +60 mV. This is consistent with a model that D-serine is a competitive antagonist on AMPA receptors. In contrast, L-serine did not exert such an inhibitory action. Consistent with this observation, we found that several D-isoforms, but not L-isoforms, of endogenous and exogenous amino acids were able to block AMPA receptors. These results indicate that there is a low affinity and stereo-selective site at the agonist binding pocket of AMPA receptors for these D-amino acids. More importantly, vesicular-released endogenous D-serine from astrocytes could potentially modulate AMPA receptors in synaptic transmission in hippocampus.     

Chronic hexosamine flux stimulates fatty acid oxidation by activating AMP-activated protein kinase in adipocytes

The hexosamine biosynthesis pathway (HBP) serves as a nutrient sensor and has been implicated in the development of type 2 diabetes. We previously demonstrated that fatty acid oxidation was enhanced in transgenic mouse adipocytes, wherein the rate-limiting enzyme of the HBP, glutamine:fructose-6-phosphate amidotransferase (GFA), was overexpressed. To explore the molecular mechanism of the HBP-induced fatty acid oxidation in adipocytes, we studied AMP-activated protein kinase (AMPK), an energy sensor that stimulates fatty acid oxidation by regulating acetyl-CoA carboxylase (ACC) activity. Phosphorylation and activity of AMPK were increased in transgenic fat pads and in 3T3L1 adipocytes treated with glucosamine to stimulate hexosamine flux. Glucosamine also stimulated phosphorylation of ACC and fatty acid oxidation in 3T3L1 adipocytes, and these stimulatory effects were diminished by adenovirus-mediated expression of a dominant negative AMPK in 3T3L1 adipocytes. Conversely, blocking the HBP with a GFA inhibitor reduced AMPK activity, ACC phosphorylation, and fatty acid oxidation. These changes are not explained by alterations in the cellular AMP/ATP ratio. Further demonstrating that AMPK is regulated by the HBP, we found that AMPK was recognized by succinylated wheat germ agglutinin, which specifically binds O-GlcNAc. The levels of AMPK in succinylated wheat germ agglutinin precipitates correlated with hexosamine flux in mouse fat pads and 3T3L1 adipocytes. Moreover, removal of O-GlcNAc by hexosaminidase reduced AMPK activity. We conclude that chronically high hexosamine flux stimulates fatty acid oxidation by activating AMPK in adipocytes, in part through O-linked glycosylation.