Arabidopsis Brassinosteroid-overproducing gulliver3-D/dwarf4-D mutants exhibit altered responses to Jasmonic acid and pathogen

Key message

Arabidopsis gulliver3 - D/dwarf4 - D displays growth-promoting phenotypes due to activation tagging of a key brassinosteroid biosynthetic gene DWARF4. In gul3-D/dwf4-D , the Jasmonate and Salicylate signaling pathways were relatively activated and suppressed, respectively.

Abstract

Energy allocation between growth and defense is elegantly balanced to achieve optimal development in plants. Brassinosteroids (BRs), steroidal hormones essential for plant growth, are regulated by other plant hormones, including auxin and jasmonates (JA); auxin stimulates the expression of a key brassinosteroid (BR) biosynthetic gene, DWARF4 (DWF4), whereas JA represses it. To better understand the interaction mechanisms between growth and defense, we isolated a fast-growing mutant, gulliver3-D (gul3-D), that resulted from the activation tagging of DWF4, and examined the response of this mutant to defense signals, including JA, Pseudomonas syringae pv. tomato (Pst DC3000) infection, and wounding. The degree of root growth inhibition following MeJA treatment was significantly decreased in gul3-1D/dwf4-5D relative to the wild type, suggesting that JA signaling is partially desensitized in gul3-1D. Quantitative RT-PCR analysis of the genes involved in JA and salicylic acid (SA) responses, including MYC2, PDF1.2, CORI3, PR1, and PR2, revealed that JA signaling was preferentially activated in gul3-1D, whereas SA signaling was suppressed. As a result, gul3-1D was more susceptible to a biotrophic pathogen, Pst DC3000. Based on our results, we propose a model in which BR and JA cooperate to balance energy allocation between growth and defense responses. In ambient conditions, BRs promote plant growth; however, when stresses trigger JA signaling, JA compromises BR signaling by downregulating DWF4 expression.     

Characterization of the Denitrification-Associated Phosphorus Uptake Properties of “Candidatus Accumulibacter phosphatis” Clades in Sludge Subjected to Enhanced Biological Phosphorus Removal

To characterize the denitrifying phosphorus (P) uptake properties of “Candidatus Accumulibacter phosphatis,” a sequencing batch reactor (SBR) was operated with acetate. The SBR operation was gradually acclimated from anaerobic-oxic (AO) to anaerobic-anoxic-oxic (A2O) conditions by stepwise increases of nitrate concentration and the anoxic time. The communities of “Ca. Accumulibacter” and associated bacteria at the initial (AO) and final (A2O) stages were compared using 16S rRNA and polyphosphate kinase genes and using fluorescence in situ hybridization (FISH). The acclimation process led to a clear shift in the relative abundances of recognized “Ca. Accumulibacter” subpopulations from clades IIA > IA > IIF to clades IIC > IA > IIF, as well as to increases in the abundance of other associated bacteria (Dechloromonas [from 1.2% to 19.2%] and “Candidatus Competibacter phosphatis” [from 16.4% to 20.0%]), while the overall “Ca. Accumulibacter” abundance decreased (from 55.1% to 29.2%). A series of batch experiments combined with FISH/microautoradiography (MAR) analyses was performed to characterize the denitrifying P uptake properties of the “Ca. Accumulibacter” clades. In FISH/MAR experiments using slightly diluted sludge (∼0.5 g/liter), all “Ca. Accumulibacter” clades successfully took up phosphorus in the presence of nitrate. However, the “Ca. Accumulibacter” clades showed no P uptake in the presence of nitrate when the sludge was highly diluted (∼0.005 g/liter); under these conditions, reduction of nitrate to nitrite did not occur, whereas P uptake by “Ca. Accumulibacter” clades occurred when nitrite was added. These results suggest that the “Ca. Accumulibacter” cells lack nitrate reduction capabilities and that P uptake by “Ca. Accumulibacter” is dependent upon nitrite generated by associated nitrate-reducing bacteria such as Dechloromonas and “Ca. Competibacter.”     

Effect of JGK-263 as a new glycogen synthase kinase-3β inhibitor on extrinsic apoptosis pathway in motor neuronal cells

Glycogen synthase kinase-3β (GSK-3β) has been identified as one of the important pathogenic mechanisms in motor neuronal death. GSK-3β inhibitor has been investigated as a modulator of apoptosis and has been shown to confer significant protective effects on cell death in neurodegenerative diseases. However, GSK-3β is known to have paradoxical effects on apoptosis subtypes, i.e., pro-apoptotic in mitochondrial-associated intrinsic apoptosis, but anti-apoptotic in death receptor-related extrinsic apoptosis. In this study, we evaluated the effect of a new GSK-3β inhibitor (JGK-263) on motor neuron cell survival and apoptosis, by using low to high doses of JGK-263 after 48 h of serum withdrawal, and monitoring changes in extrinsic apoptosis pathway components, including Fas, FasL, cleaved caspase-8, p38α, and the Fas–Daxx interaction. Cell survival peaked after treatment of serum-deprived cells with 50 μM JGK-263. The present study showed that treatment with JGK-263 reduced serum-deprivation-induced motor neuronal apoptosis by inactivating not only the intrinsic, but also the extrinsic apoptosis pathway. These results suggest that JGK-263 has a neuroprotective effect through effective modulation of the extrinsic apoptosis pathway in motor neuron degeneration.     

Therapeutic and pharmacokinetic characterizations of an anti-amyloidogenic bis-styrylbenzene derivative for Alzheimer’s disease treatment

Alzheimer’s disease drug discovery regarding exploration into the molecules and processes has focused on the intrinsic causes of the brain disorder correlated with the accumulation of amyloid-β. An anti-amyloidogenic bis-styrylbenzene derivative, KMS80013, showed excellent oral bioavailability (F = 46.2%), facilitated brain penetration (26%, iv) in mouse and target specific in vivo efficacy in acute AD mouse model attenuating the cognitive deficiency in Y-maze test. Acute toxicity (LD₅₀ >2000 mg/kg) and hERG channel inhibition (14% at 10 μM) results indicated safety of KMS80013.     

Hypoxic condition-selective upconversion via triplet–triplet annihilation based on POSS-core dendrimer complexes

The influence on the efficiencies of the triplet–triplet annihilation (TTA)-supported upconversion by oxygen under biomimetic conditions was investigated. From the solution containing the dendrimer complexes based on polyhedral oligomeric silsesquioxane (POSS)-core dendrimer with the Pt complex of octaethylporphyrin (PtOEP) and anthracene in PBS, the fluorescence emission of anthracene depending on the dissolved oxygen (DO) concentrations via the TTA-supported upconversion was obtained with the excitation light at 540 nm. In particular, we observed strong emission only under hypoxic conditions. In addition, it was found that the emission intensity via TTA-supported upconversion can be reversibly regulated by the DO concentrations in the solution.     

Infectivity of entomopathogenic nematode Steinernema carpocapsae Pocheon strain (Nematoda: Steinernematidae) on the green peach aphid Myzus persicae (Hemiptera: Aphididae) and its parasitoids

Infectivity of entomopathogenic nematode (EPN) Steinernema carpocapsae Pocheon strain on the green peach aphid Myzus persicae and its parasitic wasps (e.g., Aphidius colemani, Aphidius gifuensis and Diaeretiella rapae) was evaluated under laboratory conditions. Infective juveniles (IJs) of S. carpocapsae Pocheon strain had low infectivity against nymph and adult stages of M. persicae, showing 2% and 6.7% of mortality, respectively. Application of the EPNs had little effect on mummies caused by the three parasitoid species, allowing them to remain intact. No IJ invaded the host, regardless of EPN application rate. The parasitoid emergence from mummies ranged from 80% to 85% in the presence of EPN while 79–86% was recorded in the absence of EPN. However, the presence of the IJs reduced oviposition by the three parasitoid species, decreasing the rate up to 59% when the nematodes were applied before parasitoid release, while little difference in oviposition was observed when nematodes were applied after parasitoid release.     

Estimation of the ecosystem carbon budget in South Korea between 1999 and 2008

A carbon flux model, the vegetation integrated simulator for trace gases, was employed to estimate the carbon budgets of vegetation ecosystems in South Korea. The geographic information system was used to prepare the input variables for the model, such as climate, soil, and land-cover data, from reliable national inventories. Model simulation results indicated that the annual average gross primary production, net primary production, and soil respiration (SR) for 10 years were 91.89, 40.16, and 62.91 Tg C year^?1, respectively. The model also estimated a net ecosystem production with a value of 3.51 Tg C year^?1 between 1999 and 2008. Such results indicate that the vegetation ecosystems of South Korea offset 3.3 % of anthropogenic emissions as a net carbon sink. Latitudinal and topographical gradients over the total simulation area were found for all estimates. In addition, the estimates varied between seasons and years, especially in estimates for biomass growth and carbon uptake, because of variations in the weather conditions. Finally, model validation was conducted using measured soil efflux and flux measurement data from the Gwangneung experimental forest (GEF). The estimated SR accounted for 81.6 % of the observed SR at the GEF site (P < 0.005). Further, the model accounted well for the observed phase and amplitude of changes in the summer and autumn seasons.     

Attenuation by a Vigna nakashimae extract of nonalcoholic fatty liver disease in high-fat diet-fed mice

A Vigna nakashimae (VN) extract has been shown to have antidiabetic and anti-obesity effects. However, the mechanism underlying the effect of a VN extract on hepatic inflammation and endoplasmic reticulum (ER) stress remains unclear. In the present study, we investigated how a VN extract protects against the development of non-alcoholic fatty liver disease (NAFLD). A VN extract for 12 weeks reduced the body weight, serum metabolic parameters, cytokines, and hepatic steatosis in high-fat diet (HFD)-fed mice. A VN extract decreased HFD-induced hepatic acetyl CoA carboxylase and glucose transporter 4 expressions. In addition to the levels of high-mobility group box 1 and receptor for advanced glycation, the hepatic expression of ATF4 and caspase-3 was also reduced by a VN extract. Thus, these data indicate that a chronic VN extract prevented NAFLD through multiple mechanisms, including inflammation, ER stress, and apoptosis in the liver.     

Anti-inflammatory activity of halogenated secondary metabolites of Laurencia snackeyi (Weber-van Bosse) Masuda in LPS-stimulated RAW 264.7 macrophages

Secondary metabolites of tropical seaweed are proven to exhibit variety of biological activities. Six species of seaweed (Caulerpa racemosa var. laete-virens, Caulerpa sertularioides f. longipes, Halymenia dilatata, Laurencia snackeyi, Padina boryana, and Sargassum swartzii) were tested for anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Crude L. snackeyi extract exhibit potent activity, and upon bioassay-guided isolation, it contained four halogenated compounds that exert profound inhibitory effects against nitric oxide (NO) production in LPS-stimulated RAW 264.7 cells. These compounds were subjected to spectroscopic measurements and were identified as palisadin A (1), aplysistatin (2), 5-acetoxypalisadin B (3), and palisol (4). Further experiments showed aplysistatin (2) to significantly inhibit NO production and prostaglandin-E2 (PGE2) production, and suppress inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expression in LPS-stimulated RAW 264.7 cells. Therefore, aplysistatin (2) is suggested to inhibit NO and PGE2 production via the inhibition of iNOS and COX-2, indicating that its activity may be attributed to the modulation of anti-inflammatory agents.