Phosphatidic acid regulates ammonium uptake by interacting with AMMONIUM TRANSPORTER 1;1 in Arabidopsis.

Ammonium (NH4+) is a key inorganic nitrogen source in cellular amino acid biosynthesis. The coupling of transcriptional and posttranslational regulation of AMMONIUM TRANSPORTER (AMT) ensures that NH4+ acquisition by plant roots is properly balanced, which allows for rapid adaptation to a variety of nitrogen conditions. Here, we report that phospholipase D (PLD)-derived phosphatidic acid (PA) interacts with AMT1;1 to mediate NH4+ uptake in Arabidopsis (Arabidopsis thaliana). We examined pldα1 pldδ-knockout mutants and found that a reduced PA level increased seedling growth under nitrogen deficiency and inhibited root growth upon NH4+ stress, which was consistent with the enhanced accumulation of cellular NH4+. PA directly bound to AMT1;1 and inhibited its transport activity. Mutation of AMT1;1 R487 to Gly (R487G) resulted in abolition of PA suppression and, subsequently, enhancement of ammonium transport activity in vitro and in vivo. Observations of AMT1;1-GFP showed suppressed endocytosis under PLD deficiency or by mutation of the PA-binding site in AMT1;1. Endocytosis was rescued by PA in the pldα1 pldδ mutant but not in the mutant AMT1;1R487G-GFP line. Together, these findings demonstrated PA-based shutoff control of plant NH4+ transport and point to a broader paradigm of lipid-transporter function.

Functional analysis of indole 3-hexanoic acid as a novel auxin from Arabidopsis thaliana.

MAIN CONCLUSION: Indole 3-hexanoic acid is a novel auxin and regulates plant growth and development. Auxin is a signaling molecule that influences most aspects of plant development. Although many small bioactive molecules have been developed as auxin analogues, naturally occurring auxin and the detailed mechanisms of its specific actions in plants remain to be fully elucidated. In this study, to screen auxin responses, we used a novel picolinate synthetic auxin, 3-indole hexanoic acid (IHA), which is similar in structure to indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). IHA showed classical auxin activity in the regulation of root growth, gene expression, and PIN-FORMED abundance. Physiological and genetic analyses indicated that IHA may be perceived by the auxin receptor TIR1 and transported by the G-class ATP-binding cassette protein ABCG36 and its homolog ABCG37. Importantly, IHA was detected in planta and converted into IBA depending on the peroxisomal ß-oxidation. Together, these findings reveal a novel auxin pathway component and suggest possible undiscovered modes of auxin metabolism regulation in plants.

Sudden Death as a Sequel of Ruptured Giant Coronary Artery Aneurysm in Kawasaki Disease.

This article reports a case of Kawasaki disease (KD) and its rapid fatal course in a 5-year-old boy, who 3 days before hospitalization demonstrated fever and diffuse erythema in the face, neck, and torso, as well as swelling and pain below the right earlobe. During the admission, he was diagnosed with mumps and suspected scarlet fever. Abnormal laboratory findings included elevated values of procalcitonin, C-reactive protein, and interleukin 6. Sudden death occurred 8 days after admission. Autopsy confirmed the cause of death to be pericardial tamponade due to a ruptured, inflamed aneurysm of the left anterior descending coronary artery. We believe that any typical clinical sign of KD whenever associated with elevated indices of inflammation should set off suspicion of KD and further permit cardiovascular examination. This would contribute to distinguishing KD from other diseases with similar clinical signs in order to accelerate appropriate treatment.

Phospholipase Dδ regulates pollen tube growth by modulating actin cytoskeleton organization in Arabidopsis.

The actin cytoskeleton plays pivotal roles in pollen tube growth by regulating organelle movement, cytoplasmic streaming, and vesicle trafficking. Previous studies have reported that plasma membrane-localized phospholipase Dδ (PLDδ) binds to cortical microtubules and negatively regulates plant stress tolerance. However, it remains unknown whether or how PLDδ regulates microfilament organization. In this study, we found that loss of PLDδ function led to a significant increase in pollen tube growth, whereas PLDδ overexpression resulted in pollen tube growth inhibition. We also found that wild-type PLDδ, rather than Arg 622-mutated PLDδ, complemented the pldδ phenotype in pollen tubes. In vitro biochemical assays demonstrated that PLDδ binds directly to F-actin, and immunofluorescence assays revealed that PLDδ in pollen tubes influences actin organization. Together, these results suggest that PLDδ participates in the development of pollen tube growth by organizing actin filaments.

Progression and Regression of Abdominal Aortic Aneurysms in Mice.

OBJECTIVE: Abdominal aortic aneurysm (AAA) is a significant medical problem with a high mortality rate. Nevertheless, the underlying mechanism for the progression and regression of AAA is unknown. METHODS: Experimental model of AAA was first created by porcine pancreatic elastase incubation around the infrarenal aorta of C57BL/6 mice. Then, AAA progression and regression were evaluated based on the diameter and volume of AAA. The aortas were harvested for hematoxylin-eosin staining (HE), orcein staining, sirius red staining, immunofluorescence analysis and perls' prussian blue staining at the indicated time point. Finally, ß-aminopropionitrile monofumarate (BAPN) was used to explore the underlying mechanism of the regression of AAA. RESULTS: When we extended the observation period to 100 days, we not only observed an increase in the AAA diameter and volume in the early stage, but also a decrease in the late stage. Consistent with AAA diameter and volume, the aortic thickness showed the same tendency based on HE staining. The elastin and collagen content first degraded and then regenerated, which corresponds to the early deterioration and late regression of AAA. Then, endogenous up-regulation of lysyl oxidase (LOX) was detected, accompanying the regression of AAA, as detected by an immunofluorescent assay. BAPN and LOX inhibitor considerably inhibited the regression of AAA, paralleling the degradation of elastin lamella and collagen. CONCLUSION: Taken together, we tentatively conclude that endogenous re-generation of LOX played an influential role in the regression of AAA. Therefore, regulatory factors on the generation of LOX exhibit promising therapeutic potential against AAA.

High-Level Patchoulol Biosynthesis in Artemisia annua L.

Terpenes constitute the largest class of secondary metabolites in plants. Some terpenes are essential for plant growth and development, membrane components, and photosynthesis. Terpenes are also economically useful for industry, agriculture, and pharmaceuticals. However, there is very low content of most terpenes in microbes and plants. Chemical or microbial synthesis of terpenes are often costly. Plants have the elaborate and economic biosynthetic way of producing high-value terpenes through photosynthesis. Here we engineered the heterogenous sesquiterpenoid patchoulol production in A. annua. When using a strong promoter such as 35S to over express the avian farnesyl diphosphate synthase gene and patchoulol synthase gene, the highest content of patchoulol was 52.58 µg/g DW in transgenic plants. When altering the subcellular location of the introduced sesquiterpene synthetase via a signal peptide, the accumulation of patchoulol was observably increased to 273 µg/g DW. This case demonstrates that A. annua plant with glandular trichomes is a useful platform for synthetic biology studies.

Magnesium oxide microspheres as a packing material for the separation of basic compounds in normal-phase liquid chromatography.

Uniform monodisperse magnesium oxide microspheres with a high surface area have been prepared by a facile seed-induced precipitation. By characterizing these particles with scanning electron microscopy and N(2) physisorption techniques, the results demonstrate that these magnesium oxide microspheres have an average particle diameter of 9.5 microm, a specific surface area of 211.7 m(2)g(-1), a total pore volume of 0.76 mL g(-1), and an average pore diameter of 143 A. The chromatographic properties of these microspheres have been investigated in normal-phase mode for the separation of various basic compounds including aniline, quinoline, and pyridine derivatives. In contrast to conventional silica, the magnesium oxide particles exhibit unique selectivity and retention property for the separation of the tested basic compounds, and these microspheres are promising as an alternative new packing material for high-performance liquid chromatography.

Metabolite profiling of Arabidopsis seedlings in response to exogenous sinalbin and sulfur deficiency.

In order to determine how plant uptake of a sulfur-rich secondary metabolite, sinalbin, affects the metabolic profile of sulfur-deficient plants, gas chromatography time-of-flight mass spectrometry (GC-TOF-MS), in combination with liquid chromatography-mass spectrometry (LC-MS), was used to survey the metabolome of Arabidopsis seedlings grown in nutrient media under different sulfur conditions. The growth media had either sufficient inorganic sulfur for normal plant growth or insufficient inorganic sulfur in the presence or absence of supplementation with organic sulfur in the form of sinalbin (p-hydroxybenzylglucosinolate). A total of 90 metabolites were identified by GC-TOF-MS and their levels were compared across the three treatments. Of the identified compounds, 21 showed similar responses in plants that were either sulfur deficient or sinalbin supplemented compared to sulfur-sufficient plants, while 12 metabolites differed in abundance only in sulfur-deficient plants. Twelve metabolites accumulated to higher levels in sinalbin-supplemented than in the sulfur-sufficient plants. Secondary metabolites such as flavonol conjugates, sinapinic acid esters and glucosinolates, were identified by LC-MS and their corresponding mass fragmentation patterns were determined. Under sinalbin-supplemented conditions, sinalbin was taken up by Arabidopsis and contributed to the endogenous formation of glucosinolates. Additionally, levels of flavonol glycosides and sinapinic acid esters increased while levels of flavonol diglycosides with glucose attached to the 3-position were reduced. The exogenously administered sinalbin resulted in inhibition of root and hypocotyl growth and markedly influenced metabolite profiles, compared to control and sulfur-deficient plants. These results indicate that, under sulfur deficient conditions, glucosinolates can be a sulfur source for plants. This investigation defines an opportunity to elucidate the mechanism of glucosinolate degradation in vivo.

The responses of Arabidopsis thaliana to cadmium exposure explored via metabolite profiling.

The metabolic responses of Arabidopsis thaliana to cadmium exposure was characterized in this study. A. thaliana was cultivated in medium contaminated with different cadmium concentrations (0, 5 and 50microM, respectively) for 2weeks. Metabolite analyses were performed using gas chromatography-mass spectrometry. More than 80 metabolites characterized by retention time indices and specific mass fragments were identified. The levels of carbohydrates, organic acids, amino acids, and other stress-responsive metabolites changed under cadmium stress. Treated plants showed increased levels of Ala, beta-ala, Pro, Ser, putrescine, Suc and other metabolites with compatible solute-like properties, notably 4-aminobutyric acid, glycerol, raffinose and trehalose, compared to control (untreated) plants. Studies indicated that concentrations of antioxidants (alfa-tocopherol, campesterol, beta-sitosterol and isoflavone) also increased significantly. These results confirm the important role of antioxidant defences in the mechanisms of plant-resistance to cadmium stress. Our results suggested that metabolic profiling is a powerful tool that can rapidly classify environmentally modified plants and simplify the process of cadmium-stress responses. These data will be helpful for better understanding of mechanisms of plant adaptation to cadmium stress at the metabolite level.

Early-age characteristics of red mud-coal gangue cementitious material.

This experimental research was to investigate the possibility of incorporating red mud and coal gangue as raw materials for the production of red mud-coal gangue cementitious material, abbreviated as RGC, including analyses of its chemical composition, physical properties, mechanical properties and hydration products. The red mud and coal gangue (at a ratio of 3:2) were mixed together and shaped in small spheres with a water to solid ratio of 0.30 and then calcined at 600 degrees C for 2h. Subsequently, the RGC was prepared by blending 50% the resultant red mud-coal gangue mixtures, 24% blast-furnace slag, 20% clinker and 6% gypsum. The hydration products of RGC were characterized by XRD, TG-DTA and SEM-EDS. The results showed that it is feasible to use red mud and coal gangue to replace up to 50% of the raw materials to produce cementitious material, which can be called as silica-alumina based cementitious material. The hydration products of RGC are mostly ettringite, calcium hydroxide and C-S-H gel. As the dominant products, C-S-H gel and ettringite are principally responsible for the strength development of RGC in early hydration process. The content of Ca(OH)(2) initially increased but later was depleted after reaching the peak value at 21 days. Moreover, it is found that the composition of the C-S-H gel shifted towards higher Si, Al and Na contents with the increase of hydration age, whereas that of Ca shifted towards lower content.