Arabidopsis trigalactosyldiacylglycerol1 mutants reveal a critical role for phosphtidylcholine remodeling in lipid homeostasis.

Lipid remodeling plays a critical role in plant response to abiotic stress and metabolic perturbations. Key steps in this process involve modifications of phosphatidylcholine (PC) acyl chains mediated by lysophosphatidylcholine: acyl-CoA acyltransferases (LPCATs) and phosphatidylcholine: diacylglycerol cholinephosphotransferase (ROD1). To assess their importance in lipid homeostasis, we took advantage of the trigalactosyldiacylglycerol1 (tgd1) mutant that exhibits marked increases in fatty acid synthesis and fatty acid flux through PC due to a block in inter-organelle lipid trafficking. Here, we showed that the increased fatty acid synthesis in tgd1 is due to posttranslational activation of the plastidic acetyl-coenzyme A carboxylase. Genetic analysis showed that knockout of LPCAT1 and 2 resulted in a lethal phenotype in tgd1. In addition, plants homozygous for lpcat2 and heterozygous for lpcat1 in the tgd1 background showed reduced levels of PC and triacylglycerols (TAG) and alterations in their fatty acid profiles. We further showed that disruption of ROD1 in tgd1 resulted in changes in fatty acid composition of PC and TAG, decreased leaf TAG content and reduced seedling growth. Together, our results reveal a critical role of LPCATs and ROD1 in maintaining cellular lipid homeostasis under conditions, in which fatty acid production largely exceeds the cellular demand for membrane lipid synthesis.

A chloroplast diacylglycerol lipase modulates glycerolipid pathway balance in Arabidopsis.

Two parallel pathways compartmentalized in the chloroplast and the endoplasmic reticulum contribute to thylakoid lipid synthesis in plants, but how these two pathways are coordinated during thylakoid biogenesis and remodeling remains unknown. We report here the molecular characterization of a homologous ADIPOSE TRIGLYCERIDE LIPASE-LIKE gene, previously referred to as ATGLL. The ATGLL gene is ubiquitously expressed throughout development and rapidly upregulated in response to a wide range of environmental cues. We show that ATGLL is a chloroplast non-regioselective lipase with a hydrolytic activity preferentially towards 16:0 of diacylglycerol (DAG). Comprehensive lipid profiling and radiotracer labeling studies revealed a negative correlation of ATGLL expression and the relative contribution of the chloroplast lipid pathway to thylakoid lipid biosynthesis. Additionally, we show that genetic manipulation of ATGLL expression resulted in changes in triacylglycerol levels in leaves. We propose that ATGLL, through affecting the level of prokaryotic DAG in the chloroplast, plays important roles in balancing the two glycerolipid pathways and in maintaining lipid homeostasis in plants.

Physiological Functions of Phospholipid: Diacylglycerol Acyltransferases.

Triacylglycerol (TAG) is amongst the most energy dense storage form of reduced carbon in living systems. TAG metabolism plays critical roles in cellular energy balance, lipid homeostasis, cell growth and stress responses. In higher plants, microalgae and fungi, TAG is assembled by acyl-CoA-dependent and -independent pathways catalyzed by diacylglycerol:acyltransferase (DGAT) and phospholipid:diacylglycerol acyltransferase (PDAT), respectively. This review contains a summary of the current understanding of the physiological functions of PDATs. Emphasis is placed on their role in lipid remodeling and lipid homeostasis in response to abiotic stress or perturbations in lipid metabolism.

Efficacy of Andrographis paniculata against extended spectrum ß-lactamase (ESBL) producing E. coli.

BACKGROUND: A. paniculata is widely known for its medicinal values and is traditionally used to treat a wide range of diseases such as cancer, diabetes, skin infections, influenza, diarrhoea, etc. The phytochemical constituents of this plant possess unique and interesting biological activities. The main focus of this study was to evaluate the antibacterial property of crude ethyl acetate (CEA) extract of A. paniculata against E. coli clinical isolates along with molecular docking of 10 different bioactive components from this plant with CTX-M-15. METHODS: CEA extract was subjected to phytochemical and FTIR analysis. The E. coli isolates were tested for antibiotic susceptibility through disk-diffusion method to observe their resistance pattern towards different antibiotics. Antibacterial activity and biofilm assay were performed through broth microdilution using a 96-well microplate. CEA extract was further utilized to observe its effect on the expression of a gene encoding CTX-M-15. Finally, in-silico studies were performed where 10 different bioactive compounds from A. paniculata were molecularly docked with CTX-M-15. RESULTS: Phytochemical and FTIR analysis detected the presence of various secondary metabolites and functional groups in CEA extract respectively. Molecular docking provided the number of residues and bond lengths together with a positive docking score. Antibiotic susceptibility showed the multi-drug resistance of all the clinical strains of E. coli. The antibacterial and antibiofilm efficiency of CEA extract (25, 50 and 100 µg/ml) was tested and 100 µg/ml of the extract was more effective in all the strains of E. coli. All 3 ESBL producing strains of E. coli were subjected to gene expression analysis through PCR. Strains treated with 100 µg/ml of the extract showed a downregulation of the gene encoding CTX-M-15 compared to untreated controls. CONCLUSIONS: The utilization of CEA extract of A. paniculata proved an economical way of controlling the growth and biofilm formation of ESBL strains of E. coli. CEA extract was also able to downregulate the expression of a gene encoding CTX-M-15. Molecular docking of 10 different bioactive compounds from A. paniculata with CTX-M-15 provided the residues and bond lengths with a positive docking score.

Effect of high-fat diet on cognitive impairment in triple-transgenic mice model of Alzheimer's disease.

High-fat diet (HFD)-induced obesity is a risk factor for cognitive impairment in Alzheimer's disease (AD). It has been reported that two typical neuropathological markers of AD, ß-amyloid (Aß) peptide and hyperphosphorylated protein tau can cause neuronal apoptosis via oxidative stress, which ultimately leads to cognitive dysfunction. In this study, we tried to explore the molecular pathway underlying memory impairment in young AD transgenic mice model in response to HFD. We maintained non-transgenic control mice (non-Tg) and triple transgenic AD (3xTg-AD) mice aged 8 weeks on either normal diet (ND) containing 10% fat or HFD (60% fat) for 16 weeks. Cognitive functions were evaluated by Morris water maze and Y-maze tests. Behavioral tests showed a significant memory impairment in 3xTg-AD mice fed with HFD. HFD did not alter the levels of Aß and phospho-tau protein in the cortical region regardless of groups. However, 3xTg-AD mice fed with HFD exhibited increased neuronal oxidative stress and apoptosis as assessed by augmentation of lipid peroxidation, activation of caspase-3 and elevated ratio of Bax/Bcl-2. Furthermore, HFD markedly reduced the activation of redox-sensitive transcription factor NF-E2-related factor 2 (Nrf2) by suppressing its up-stream regulatory protein kinase B/Akt as well as down-stream targets such as heme oxygenase-1 and manganese superoxide dismutase in these mice. Our findings suggest that HFD may accelerate cognitive impairment by enhancing oxidative stress and aggravating neuronal apoptosis via inactivation of Nrf2 signaling pathway.

Silicon Enhances Plant Vegetative Growth and Soil Water Retention of Soybean (Glycine max) Plants under Water-Limiting Conditions.

Silicon has been implicated as a factor affecting the degree of resistance to abiotic stresses in several plant species. However, the role of silicon in soybean (Glycine max) under water-limiting conditions is not yet fully understood. This study was conducted to evaluate the effects of silicon application on the vegetative growth of two soybean cultivars (Asgrow 5332 and Progeny 5333) grown under water-limiting conditions. Silicon was provided by adding silicate to the soil. Water-limiting treatments were imposed on plants at two vegetative growth stages for 20 days by irrigating with a reduced amount of water (66% or 33% of the required water). Silicate application enhanced plant height, leaf area, and total dry weight of soybean plants. Significant increases in root volumes were observed in both the silicate-treated cultivars compared to the control plants under water-limiting conditions (33% irrigation). Net photosynthesis and stomatal conductance were decreased, but the quantum efficiency of photosystem II (Fv'/Fm') did not change under the same irrigation condition, which indicates photosynthesis downregulation through stomatal limitation. Silicate-treated plants in both cultivars had higher water use efficiency as compared to control plants under water-limiting conditions (irrigated with 66% or 33% of required water). Under water-limiting conditions, the soil moisture content was significantly higher in pots containing silicate than in those without added silicate, suggesting that silicon application improves water holding capacity. Taken together, the results from this study indicate that silicon application can improve the vegetative growth of soybeans under low water conditions by increasing the water use efficiency of plants and enhancing the soil's ability to retain moisture.

Proteomic analysis response of rice (Oryza sativa) leaves to ultraviolet-B radiation stress.

Rice (Oryza sativa) is a human staple food and serves as a model organism for genetic and molecular studies. Few studies have been conducted to determine the effects of ultraviolet-B (UV-B) stress on rice. UV-B stress triggers morphological and physiological changes in plants. However, the underlying mechanisms governing these integrated responses are unknown. In this study, we conducted a proteomic response of rice leaves to UV-B stress using two-dimensional gel electrophoresis and identified the selected proteins by mass spectrometry analysis. Four levels of daily biologically effective UV-B radiation intensities were imposed to determine changes in protein accumulation in response to UV-B stress: 0 (control), 5, 10, and 15 kJ m-2 d-1in two cultivars, i.e., IR6 and REX. To mimic the natural environment, we conducted this experiment in Sunlit Soil-Plant-Atmosphere-Research (SPAR) chambers. Among the identified proteins, 11% of differentially expressed proteins were found in both cultivars. In the Rex cultivar, only 45% of proteins are differentially expressed, while only 27.5% were expressed in IR6. The results indicate that REX is more affected by UV-B stress than IR6 cultivars. The identified protein TSJT1 (spot 16) in both cultivars plays a crucial role in plant growth and development during stress treatment. Additionally, we found that UV-B stress altered many antioxidant enzymes associated with redox homeostasis and cell defense response. Another enzyme, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH), has been identified as spot 15, which plays an essential role in glycolysis and cellular energy production. Another vital protein identified is glycosyl hydrolase (GH) as spot 9, which catalyzes the hydrolysis of glycosidic bonds in cell wall polymers and significantly affects cell wall architecture. Some identified proteins are related to photosynthesis, protein biosynthesis, signal transduction, and stress response. The findings of our study provide new insights into understanding how rice plants are tailored to UV-B stress via modulating the expression of UV-B responsive proteins, which will help develop superior rice breeds in the future to combat UV-B stress. Data are available via ProteomeXchange with identifier PXD032163.

Genetic Variability Assessment of Tropical Indica Rice (Oryza sativa L.) Seedlings for Drought Stress Tolerance.

Drought stress is one of the most devastating abiotic factors limiting plant growth and development. Devising an efficient and rapid screening method at the seedling stage is vital in identifying genotypes best suited under drought conditions. An experiment was conducted to assess 74 rice genotypes for drought tolerance using specially designed mini-hoop structures. Two treatments were imposed on rice seedlings, including 100% moisture and a 50% moisture regime. Several shoot morpho-physiological traits and root traits were measured and analyzed. The genotypes exhibited a wide range of variability for the measured traits, with the leaf area showing the most significant variation, followed by plant height, tiller number, and shoot dry weight. In contrast, the drought did not significantly affect most root traits. The germplasm was classified into different categories using cumulative drought stress response indices (CDSRI); 19 genotypes (26%) were identified as drought sensitive, and 33 (45%), 15 (20%), and 7 (9%) were determined as low, moderately, and highly drought-tolerant, respectively. Genotypes IR86638 and IR49830 were the most and least drought-tolerant, respectively. Overall, a poor correlation was observed between CDSRI, total shoot traits (R2 = 0.36), and physiological parameters (R2 = 0.10). A strong linear correlation was found between CDSRI and root traits (R2 = 0.81), suggesting that root traits are more crucial and better descriptors in screening for drought tolerance. This study can help rice breeders and scientists to accelerate breeding by adopting a mini-hoop rapid screening method. The tolerant genotypes could serve as appropriate donor parents, progenies, and potential genotypes for developing drought-tolerant commercial cultivars.

Andrographis paniculata extract inhibit growth, biofilm formation in multidrug resistant strains of Klebsiella pneumoniae.

BACKGROUND AND AIM: Andrographis paniculata (Kalmegh), a valuable ancient medicinal herb is used in the treatment of several diseases in most Asian countries including India. Klebsiella pneumoniae is an opportunistic pathogen causing nosocomial infections in human. We have investigated the antimicrobial susceptibility and the presence of AmpC gene in K. pneumoniae strain isolated from the sputum of the patient. EXPERIMENTAL PROCEDURE: Antibiotic susceptibility test and phenotypic detection of AmpC/ESBL beta-lactamase were performed by combined disc diffusion test. The CEA of A. paniculata was analyzed for its antibacterial potential against susceptible and resistant strains of K. pneumoniae through the broth microdilution method. Molecular detection of AmpC gene was carried by polymerase chain reaction (PCR). RESULTS: Antibiotic susceptibility test displayed that the clinical isolate of K. pneumoniae were resistant towards cephalosporins, quinolone and monobactam but susceptible to carbapenems. Combined disk diffusion demonstrated AmpC+ve/ESBL-ve beta-lactamase. 250 µg/ml of CEA extract confirmed the inhibition of bacterial growth and biofilm formation compared to the antibiotic. CEA treated K. pneumoniae displayed a reduction of AmpC by polymerase chain reaction. CONCLUSION: The present study illustrates that CEA extract of A. paniculata demonstrated potentiality to control K. pneumoniae growth and biofilm formation. CEA was able to suppress the expression of gene encoding AmpC. This study proves to be an economical approach to control the growth of K. pneumoniae which causes serious infections.