Capping the hydroxyl groups (-OH) of α-cellulose to reduce Hy-groscopicity for accurate O/O measurement by EA/Py/IRMS.

Obtaining an accurate measurement of O/O at natural abundance level for land plants-derived α-cellulose with the currently popular EA/Py/IRMS (elemental analysis/pyrolysis/isotope ratio mass spectrometry) method is a challenge due to the hygroscopic nature of the exposed hydroxyl groups, as the O/O of adsorbed moisture is usually different from that of the α-cellulose and the relative amount of adsorbed moisture is sample- and relative humidity-dependent. To minimize the hygroscopicity-related measurement error, we capped the hydroxyl groups of α-cellulose by benzylation to various degrees and found that the O/O ratio of α-cellulose increased with the degree of benzyl substitution (DS), consistent with the theoretical prediction that a reduced presence of exposed hydroxyl groups should lead to a more accurate (and therefore more reliable) α-cellulose O/O measurement. We propose the establishment of a moisture adsorption-degree of substitution or percentage of oxygen-O/O ratio equation, based on the measurement of C%, O% and δO of variably capped α-cellulose, so that a robust correction can be made in a plant species- and laboratory conditions-specific manner.

On the Chemical Purity and Oxygen Isotopic Composition of α-Cellulose Extractable from Higher Plants and the Implications for Climate, Metabolic, and Physiological Studies.

The O/O ratio of α-cellulose in land plants has proved of interest for climate, environmental, physiological, and metabolic studies. Reliable application of such a ratio may be compromised by the presence of hemicellulose impurities in the α-cellulose product obtainable with current extraction methods, as the impurities are known to be isotopically different from that of the α-cellulose. We first compared the quality of hydrolysates of "α-cellulose products" obtained with four representative extraction methods (Jayme and Wise; Brendel; Zhou; Loader) and quantified the hemicellulose-derived non-glucose sugars in the α-cellulose products from 40 land grass species using gas chromatography-mass spectrometry (GC/MS).

Combining Heat Stress with Pre-Existing Drought Exacerbated the Effects on Chlorophyll Fluorescence Rise Kinetics in Four Contrasting Plant Species.

Although drought and high temperature are two main factors affecting crop productivity and forest vegetation dynamics in many areas worldwide, little work has been done to describe the effects of heat combined with pre-existing drought on photochemical function in diverse plant species. This study investigated the biophysical status of photosystem II (PSII) and its dynamic responses under 2-day heat stress during a 2-week drought by measuring the polyphasic chlorophyll fluorescence rise (OJIP) kinetics. This study examined four contrasting species: a C3 crop/grass (wheat), a C4 crop/grass (sorghum), a temperate tree species () and a tropical tree species ().

One-Pot Extractive Transesterification of Fatty Acids Followed by DMOX Derivatization for Location of Double Bonds Using GC-EI-MS.

Fatty acids are an essential structural and energy storage component of cells and hence there is much interest in their metabolism, requiring identification and quantification with readily available instrumentation, such as GC-MS. Fatty acid methyl esters (FAMEs) can be generated and extracted directly from biological tissue, in a one-pot process, and following high resolution GC, their respective chain length, degrees of unsaturation, and other functionalities can be readily identified using EI-MS. Defining the positions of the double bonds in the alkyl chain requires conversion of the FAMEs into their respective dimethyloxazoline (DMOX) derivatives.

The effect of processing medium on the H/ H of carbon-bound hydrogen in α-cellulose extracted from higher plants.

Rationale: Although the H/ H ratio of the carbon-bound hydrogens (C-Hs) in α-cellulose extracted from higher plants has long been used successfully for climate, environmental and metabolic studies, the assumption that bleaching with acidified NaClO to remove lignin before pure α-cellulose can be obtained does not alter the H/ H ratio of α-cellulose C-Hs has nonetheless not been tested.

Methods: For reliable application of the H/ H ratio of α-cellulose C-H, we processed plant materials representing different phytochemistries and photosynthetic carbon assimilation modes in isotopically contrasting bleaching media (with an isotopic difference of 273 mUr). All the isotope ratios were measured by elemental analyzer/isotope ratio mass spectrometry (EA/IRMS).

Headspace solid-phase microextraction coupled to gas chromatography-mass spectrometry with selected ion monitoring for the determination of four food flavoring compounds and its application in identifying artificially scented rice.

The adulteration of rice using synthetic aromatic flavorings to fraudulently imitate commercially valuable fragrant rice varieties has attracted extensive attention from regulatory authorities around the world. In order to get convincing evidence of adulteration, appropriate scientific analytical methods need to be developed. In this study, a simple and efficient headspace solid-phase microextraction (HS SPME) technique coupled with gas chromatography mass spectrometry using selected ion monitoring (GC-MS-SIM) for the determination of four food flavoring compounds which are possibly used as adulterants is proposed.

Calcium homeostasis during hibernation and in mechanical environments disrupting calcium homeostasis.

To maintain calcium homeostasis during physical inactivity, precise coordination is necessary between different organs of the body. There are a number of factors which alter an organism's calcium balance, such as growth, aging, physical inactivity and acquired or inherited disorders which ultimately lead to bone loss. In non-hibernating mammals, physical inactivity causes bone loss which may not be completely recoverable during the lifespan of an individual despite a resumption of activity.

ERECTA receptor-kinases play a key role in the appropriate timing of seed germination under changing salinity.

Appropriate timing of seed germination is crucial for the survival and propagation of plants, and for crop yield, especially in environments prone to salinity or drought. However, the exact mechanisms by which seeds perceive changes in soil conditions and integrate them to trigger germination remain elusive, especially once the seeds are non-dormant. In this study, we determined that the Arabidopsis ERECTA (ER), ERECTA-LIKE1 (ERL1), and ERECTA-LIKE2 (ERL2) leucine-rich-repeat receptor-like kinases regulate seed germination and its sensitivity to changes in salt and osmotic stress levels.

Occurrence and distribution of unsubstituted B-ring flavanones in Eucalyptus foliage.

A group of plant specialised metabolites (PSMs) collectively known as unsubstituted B-ring flavanones (UBFs) have previously been found in the foliage of some species from the genus Eucalyptus L'Hér. (Myrtaceae), specifically from the subgenus Eucalyptus (monocalypts). Captive feeding studies using artificial diets suggest that these compounds may potentially influence the feeding preferences of marsupial folivores, such as koalas.

The Synthesis of ³H-Labelled 8-Azido-N⁶-Benzyladenine and Related Compounds for Photoaffinity Labelling of Cytokinin-Binding Proteins.

The biology of the group of plant hormones termed cytokinins is reviewed to reveal areas where further studies of cytokinin-binding proteins could be significant. Such areas include: inhibition of human tumour cell growth by cytokinin ribosides, the role of cytokinins in the development of diverse micro-organisms including the cyanobacteria and , the very rapid responses of plant cells to exogenous cytokinins, and other aspects of cytokinin plant biology. Photoaffinity labelling (PAL) coupled to the recent advances in HPLC of proteins and mass spectral analysis and sequencing of proteins, may have relevance to these areas.

Novel Position-Specific O/O Measurement of Carbohydrates. I. O-3 of Glucose and Confirmation of O/O Heterogeneity at Natural Abundance Levels in Glucose from Starch in a C Plant.

The O/O ratio at both molecular and positional levels in the carbohydrates of higher plants is a reliable proxy for the plant growth environment, and a potential indicator of the plant photosynthetic carbon assimilation mode, and its physiological, biochemical and metabolic status. The lack of exploitable nuclear resonance in O and O and the extremely low O abundance make the NMR-based PSIA (position-specific isotopic analysis) a significant challenge. In this Article, an alternative three-step wet chemistry based method for accessing the O/O of glucose O-3 is presented.

Promotion of mammalian angiogenesis by neolignans derived from soybean extracellular fluids.

Excessive or insufficient angiogenesis is associated with major classes of chronic disease. Although less studied, small molecules which can promote angiogenesis are being sought as potential therapeutics for cardiovascular and peripheral arterial disease and stroke. Here we describe a bioassay-directed discovery approach utilising size exclusion and liquid chromatography to purify components of soybean xylem sap that have pro-angiogenic activity.

Plasticity of photosynthetic heat tolerance in plants adapted to thermally contrasting biomes.

In many biomes, plants are subject to heatwaves, potentially causing irreversible damage to the photosynthetic apparatus. Field surveys have documented global, temperature-dependent patterns in photosynthetic heat tolerance (P ); however, it remains unclear if these patterns reflect acclimation in P or inherent differences among species adapted to contrasting habitats. To address these unknowns, we quantified seasonal variations in T (high temperature where minimal chlorophyll-a fluorescence rises rapidly, reflecting disruption to photosystem II) in 62 species native to 6 sites from 5 thermally contrasting biomes across Australia.

On the contributions of photorespiration and compartmentation to the contrasting intramolecular H profiles of C and C plant sugars.

Compartmentation of C photosynthetic biochemistry into bundle sheath (BS) and mesophyll (M) cells, and photorespiration in C plants is predicted to have hydrogen isotopic consequences for metabolites at both molecular and site-specific levels. Molecular-level evidence was recently reported (Zhou et al., 2016), but evidence at the site-specific level is still lacking.

Hydrogen isotopic differences between C and C land plant lipids: consequences of compartmentation in C photosynthetic chemistry and C photorespiration.

The H/ H ratio of carbon-bound H in biolipids holds potential for probing plant lipid biosynthesis and metabolism. The biochemical mechanism underlying the isotopic differences between lipids from C and C plants is still poorly understood. GC-pyrolysis-IRMS (gas chromatography-pyrolysis-isotope ratio mass spectrometry) measurement of the H/ H ratio of leaf lipids from controlled and field grown plants indicates that the biochemical isotopic fractionation (ε H ) differed between C and C plants in a pathway-dependent manner: ε H  > ε H for the acetogenic pathway, ε H  < ε H for the mevalonic acid pathway and the 1-deoxy-D-xylulose 5-phosphate pathway across all species examined.

A role for jasmonates in the release of dormancy by cold stratification in wheat.

Hydration at low temperatures, commonly referred to as cold stratification, is widely used for releasing dormancy and triggering germination in a wide range of species including wheat. However, the molecular mechanism that underlies its effect on germination has largely remained unknown. Our previous studies showed that methyl-jasmonate, a derivative of jasmonic acid (JA), promotes dormancy release in wheat.

Factors Altering Pyruvate Excretion in a Glycogen Storage Mutant of the Cyanobacterium, Synechococcus PCC7942.

Interest in the production of carbon commodities from photosynthetically fixed CO2 has focused attention on cyanobacteria as a target for metabolic engineering and pathway investigation. We investigated the redirection of carbon flux in the model cyanobacterial species, Synechococcus elongatus PCC 7942, under nitrogen deprivation, for optimized production of the industrially desirable compound, pyruvate. Under nitrogen limited conditions, excess carbon is naturally stored as the multi-branched polysaccharide, glycogen, but a block in glycogen synthesis, via knockout mutation in the gene encoding ADP-glucose pyrophosphorylase (glgC), results in the accumulation of the organic acids, pyruvate and 2-oxoglutarate, as overflow excretions into the extracellular media.

Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1.

Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type.

Jasmonic acid is associated with resistance to twospotted spider mites in diploid cotton (Gossypium arboreum).

The twospotted spider mite (Tetranychus urticae Koch) is capable of dramatically reducing the yield of cotton crops and is often difficult and expensive to control. This study investigated and compared two important plant hormones, jasmonic acid (JA) and salicylic acid (SA), as constitutive and/or induced defence response components in a mite susceptible commercial cotton cultivar, Sicot 71 (Gossypium hirsutum L.) and a resistant diploid cotton BM13H (Gossypium arboreum L.

Alteration of flavonoid accumulation patterns in transparent testa mutants disturbs auxin transport, gravity responses, and imparts long-term effects on root and shoot architecture.

Flavonoids have broad cross-kingdom biological activity. In Arabidopsis, flavonoid accumulation in specific tissues, notably the root elongation zone and root/shoot junction modulate auxin transport, affect root gravitropism, and influence overall plant architecture. The relative contribution made by aglycones and their glycosides remains undetermined, and the longer-term phenotypic effects of altered flavonoid accumulation are not fully assessed.

The anisotropy1 D604N mutation in the Arabidopsis cellulose synthase1 catalytic domain reduces cell wall crystallinity and the velocity of cellulose synthase complexes.

Multiple cellulose synthase (CesA) subunits assemble into plasma membrane complexes responsible for cellulose production. In the Arabidopsis (Arabidopsis thaliana) model system, we identified a novel D604N missense mutation, designated anisotropy1 (any1), in the essential primary cell wall CesA1. Most previously identified CesA1 mutants show severe constitutive or conditional phenotypes such as embryo lethality or arrest of cellulose production but any1 plants are viable and produce seeds, thus permitting the study of CesA1 function.

Temperature modulation of fatty acid profiles for biofuel production in nitrogen deprived Chlamydomonas reinhardtii.

This study investigated the changes in the fatty acid content and composition in the nitrogen-starved Chlamydomonas reinhardtii starchless mutant, BAF-J5, grown at different temperatures. The optimal temperature for vegetative growth under nitrogen sufficient conditions was found to be 32 °C. Shifting temperature from 25 to 32 °C, in conjunction with nitrogen starvation, resulted in BAF-J5 storing the maximum quantity of fatty acid (76% of dry cell weight).

Cortical microtubules optimize cell-wall crystallinity to drive unidirectional growth in Arabidopsis.

The shape of plants depends on cellulose, a biopolymer that self-assembles into crystalline, inextensible microfibrils (CMFs) upon synthesis at the plasma membrane by multi-enzyme cellulose synthase complexes (CSCs). CSCs are displaced in directions predicted by underlying parallel arrays of cortical microtubules, but CMFs remain transverse in cells that have lost the ability to expand unidirectionally as a result of disrupted microtubules. These conflicting findings suggest that microtubules are important for some physico-chemical property of cellulose that maintains wall integrity.

Fatty acid profiling of Chlamydomonas reinhardtii under nitrogen deprivation.

The Chlamydomonas reinhardtii starch-less mutant, BAF-J5, was found to store lipids up to 65% of dry cell weight when grown photoheterotrophically and subjected to nitrogen starvation. Fourier transform infrared spectroscopy was used as a high-throughput method for semi-quantitative measurements of protein, carbohydrate and lipid content. The fatty acids of wild-type and starch mutants were identified and quantified by gas chromatography mass spectrometry.

Freeze avoidance: a dehydrating moss gathers no ice.

Using cryo-SEM with EDX fundamental structural and mechanical properties of the moss Ceratodon purpureus (Hedw.) Brid. were studied in relation to tolerance of freezing temperatures.