Juanjuan Chen

Quantitative profiling method for phytohormones and betaines in algae by liquid chromatography electrospray ionization tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for the quantitative determination of phytohormones and betaines in algae. The results showed that phytohormones and betaines were separated with high efficiency on Hypersil Gold C18 and Cnwsil SCX columns. Mass spectrometric detection was performed using positive or negative electrospray ionization in selective reaction monitoring mode (SRM). Linearity of the method was good with correlation coefficients (r(2) > 0.9951 in the range of 0.005-5 mg/L. The limits of detection were from 0.004 to 0.86 µg/L and the limits of quantification were in the range from 0.01 to 2.8 µg/L for the investigated phytohormones and betaines. The obtained recoveries varied between 61.33 and 90.39%, and the relative standard deviations were <15%. Using the developed methods, seven types of phytohormones and two types of betaines in Laminaria japonica, and seven types of phytohormones and one type of betaine in Pyropia haitanensis, which were collected in Xiangshan, Zhejiang Province, China, were determined. Thus, LC-MS/MS was demonstrated to be a powerful tool for the comprehensive analysis of phytohormones and betaines in algae, owing to its large dynamic range and excellent sensitivity.

A Lipoxygenase from Red Alga Pyropia haitanensis, a Unique Enzyme Catalyzing the Free Radical Reactions of Polyunsaturated Fatty Acids with Triple Ethylenic Bonds

Lipoxygenases (LOXs) are key enzymes to regulate the production of hormones and defensive metabolites in plants, animals and algae. In this research, a full length LOX gene has been cloned and expressed from the red alga Pyropia haitanensis (Bangiales, Rhodophyta) gametophyte (PhLOX2). Subsequent phylogenetic analysis showed that such LOX enzymes are separated at the early stage of evolution, establishing an independent branch. The LOX activity was investigated at the optimal pH of 8.0. It appears that PhLOX2 is a multifunctional enzyme featuring both lipoxygenase and hydroperoxidase activities. Additionally, PhLOX2 exhibits remarkable substrate and position flexibility, and it can catalyze an array of chemical reactions involving various polyunsaturated fatty acids, ranging from C18 to C22. As a matter of fact, mono-hydroperoxy, di-hydroperoxy and hydroxyl products have been obtained from such transformations, and eicosapentaenoic acid seem to be the most preferred substrate. It was found that at least triple ethylenic bonds are required for PhLOX2 to function as a LOX, and the resulting hydroxy products should be originated from the PhLOX2 mediated reduction of mono-hydroperoxides, in which the hydrogen abstraction occurs on the carbon atom between the second and third double bond. Most of the di-hydroperoxides observed seem to be missing their mono-position precursors. The substrate and position flexibility, as well as the function versatility of PhLOXs represent the ancient enzymatic pathway for organisms to control intracellular oxylipins.

Profiling lipidome changes of Pyropia haitanensis in short-term response to high-temperature stress

Based on the growing concern for global warming, changes in the lipid profile of the red alga Pyropia haitanensis were examined under different high temperatures. Lipidomes of P. haitanensis cultured at 20xa0°C as the control group, and 25, 28, and 35xa0°C as the high-temperature group, were systematically characterized using ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and multivariate statistical analysis. Lipidomics analysis identified a total of 39 lipids as lipid biomarkers belonging to the classes including DAG, DGDG, Lyso-MGDG, Lyso-DGDG, SQDG, Lyso-SQDG, Lyso-PA, Lyso-PC, Lyso-PE, Lyso-PI, Lyso-PG, and PIP. The levels of glycolipids, Lyso-PE, Lyso-PI, Lyso-PG, and PIP decreased as the culture temperature increased from 20 to 35xa0°C. Biomarker-based heat map and box-plots showed the differences in lipid biomarker expression among the four elevated temperatures. The up- or downregulation of these lipid biomarkers offers plausible physiological insights into lipid metabolism in P. haitanensis in response to high-temperature stress.

Simultaneous determination of peimine and peiminine in rat plasma by LC‐ESI‐MS employing solid‐phase extraction

A simple and reliable LC-ESI-MS method for the determination of peimine and peiminine in rat plasma was developed for the first time. The method was proven to be specific and sensitive by carrying out validation. The analytes were extracted from rat plasma via solid-phase extraction on Waters Oasis MCX cartridges. Chromatography separation was achieved on a C(18) column using 10 mM ammonium acetate (adjusted to pH 3.0 with glacial acetic acid)-acetonitrile (85:15, v/v) as mobile phase. The linear range was 1-100 ng/mL for peimine and peiminine. Intra- and inter-day precisiond were less than 10%. Accuracies were within 85-115% of their nominal concentrations. The limit of quantification was 1 ng/mL for both analytes. The developed assay was successfully applied to pharmacokinetic study of peimine and peiminine in rats orally administered the alkaloids extracts from Bulbus Fritillariae, demonstrating a possible broader spectrum of applications of this method.

Flg22-triggered oxylipin production in Pyropia haitanensis

This study provides evidence that flg22, the most conserved 22‐amino acid peptide in the N‐terminal part of bacterial flagellin can trigger the defense responses of Pyropia haitanensis (Bangiales, Rhodophyta). The defense responses are a chain of events including release of H2O2 and free unsaturated fatty acids C20:4, consumption of C18:3, and the chemical or enzymatic oxidation of both C20 and C18 polyunsaturated fatty acids. Oxidized C20 and C18 fatty acids lead to the production of corresponding hydroperoxy and hydroxylated derivatives, such as 9‐hydroperoxy octadecadienoic acid, 8‐hydroperoxy eicosapentaenoic acid, and 8‐hydroxyl eicosapentaenoic acid, which could be further oxidatively metabolized to yield saturated aldehydes and ketone. Changes of three typical hormones jasmonate, methyl jasmonate, and salicylic acid were observed. Contrary to the increase of jasmonate and methyl jasmonate, salicylic acid was decreased. The expression of key enzymes of oxylipin pathway PhLOX and PhLOX2 were upregulated. However, some defense and antioxidant related genes including PhHsp 70, Phsod , and PhRboh were downregulated markedly at the early stage of flg22 challenge. Overall, our results imply that red algae have evolved a similar defense response and may share the conservative‐recognizing receptor for flg22 as in higher plants.

Glycerol‐3‐phosphate metabolism plays a role in stress response in the red alga Pyropia haitanensis

Glycerol‐3‐phosphate (G3P) has been suggested as a novel regulator of plant defense signaling, however, its role in algal resistance remains largely unknown. The glycerol kinase (also designated as NHO1) and NAD‐dependent G3P dehydrogenase (GPDH) are two key enzymes involved in the G3P biosynthesis. In our study, we cloned the full‐length cDNA of NHO1 (NHO1Ph) and GPDH (GPDHPh) from the red alga Pyropia haitanensis (denoted as NHO1Ph and GPDHPh) and examined their expression level under flagellin peptide 22 (flg22) stimulation or heat stress. We also measured the level of G3P and floridoside (a downstream product of G3P in P. haitanensis) under flg22 stimulation or heat stress. Both NHO1Ph and GPDHPh shared high sequence identity and structural conservation with their orthologs from different species, especially from red algae. Phylogenetic analysis showed that NHO1s and GPDHs from red algae were closely related to those from animals. Under flg22 stimulation or heat stress, the expression levels of NHO1Ph and GPDHPh were up‐regulated, G3P levels increased, and the contents of floridoside decreased. But the floridoside level increased in the recovery period after heat stress. Taken together, we found that G3P metabolism was associated with the flg22‐induced defense response and heat stress response in P. haitanensis, indicating the general conservation of defense response in angiosperms and algae. Furthermore, floridoside might also participate in the stress resistance of P. haitanensis.

Determination of Floridoside and Isofloridoside in Red Algae by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

A facile method based on liquid chromatography coupled with triple quadrupole mass spectrometry was established to determine floridoside and isofloridoside in red algae. Correlation coefficients of the calibration curves were larger than 0.9989, indicated good linearity. Detection limits of floridoside and isofloridoside were 0.05 and 0.20 ng/mL, respectively, and the limits of quantification were 0.1 and 0.4 ng/mL. The recoveries varied from 75.7% to 76.8%, and relative standard deviations of inter-day and intra-day precision were lower than 8.5% (n = 5). The effects of sea level variations in the intertidal zone on the osmotic role of floridoside and isofloridoside concentrations in seven red algae were investigated. It was shown that algae that inhabit higher levels in the intertidal zone contained higher concentrations of floridoside and isofloridoside. The results suggest that the presence of direct sun, exposure time, and temperature influenced to the concentrations of floridoside and isofloridoside due to the osmotic pressure adjustments.

Analysis of global metabolome by gas chromatography-mass spectrometry of Pyropia haitanensis stimulated with 1-octen-3-ol

Abstract1-Octen-3-ol is a major volatile metabolite produced by red seaweed Pyropia haitanensis under stresses. Using a metabolic profiling approach, we identified metabolites in P. haitanensis affected by 1-octen-3-ol treatment. The thalli were exposed to 1-octen-3-ol for 0.5 and 1xa0h. Using a non-targeted GC-MS analysis, 246 peaks in control and 1-octen-3-ol-treated P. haitanensis were detected. Among them, 72 metabolites were identified. Further statistical analysis revealed that these 72 metabolites covered different types of primary metabolism and secondary metabolism pathways, including organic acids, carbohydrates, amino acids, glycols, and fatty acids. PCA and PLS-DA analyses revealed that the metabolic composition differed between the control and 1-octen-3-ol-treated samples, and the main metabolites contributing to the dispersion were fatty acid, citric acid, some sugars, and amino acids. However, the metabolic compositions between two 1-octen-3-ol-treated samples (0.5 and 1xa0h) were similar. Pyropia haitanensis treated with 1-octen-3-ol showed reduced levels of certain free fatty acids and an increased level of monoacylglycerol. In addition, the synthesis of many amino acids and photosynthetic product galactosylglycerol was increased, along with some essential metabolites in the primary metabolic pathways, such as glycerol-3-phosphate, organic acids, and others. These results indicated that P. haitanensis recognized 1-octen-3-ol, which accelerated its primary metabolism to promote cell growth under stresses. These findings provided useful information on how algae respond to stress-induced signal.

Heat shock-induced metabolic conversion of membrane lipids, fatty acids and volatile organic compounds of Pyropia haitanensis under different heat shock time: Lipidomics of Pyropia haitanensis

Lipid metabolites play an important role in understanding the stress physiology of Pyropia haitanensis, and can be used to facilitate development of stress‐resistant Pyropia cultivars. Therefore, in this study ultra performance liquid chromatography coupled with quadrupole time of flight mass spectrometry (UPLC‐Q‐TOF‐MS) and gas chromatography–mass spectrometry (GC–MS) based metabolomics approaches were developed to screen the responses of lipid metabolites such as phospholipids, glycolipids, fatty acids and volatile organic compounds (VOCs) to different heat shock times. A total of 26 potential lipid biomarkers including Lyso‐monogalactosyldiacylglycerol (Lyso‐MGDG), Lyso‐digalactosyldiacylglycerol (Lyso‐DGDG), sulfoquinovosylmonoacylglycerols (SQMG), sulfoquinovosyldiacylglycerol (SQDG), diacylglyceryltrimethylhomoserine (DGTS), triacylglycerol (TAG), Lyso‐phosphatidicacid (Lyso‐PA), Lyso‐phosphatidylcholine (Lyso‐PC), Lyso‐phosphatidylethanolamine (Lyso‐PE), Lyso‐phosphatidylglycerol (Lyso‐PG), phosphatidylglycerol (PG), phosphatidylinositol (PI), and phosphatidylinositol phosphate (PIP) were identified, most of which responded to high temperature by reducing or increasing levels after stimulation for 1u2009h or 6u2009h. After times longer than 6u2009h, the levels of most lipids gradually recovered to the control group levels. Moreover, the balance of lipids and fatty acids transformation was disrupted. Overall, 11 total fatty acids (TFAs), 13 free fatty acids (FFAs) and 29 VOCs were identified during 0–72u2009h of high temperature stress. The FFAs, especially polyunsaturated C 20 fatty acids and VOCs, showed opposing change trends, indicating the transformation between C 20 fatty acids and VOCs. Overall, this study provides important insights into the metabolic variations of P. haitanensis under different heat shock time and the relationship between the conversion of lipids, fatty acids, and VOCs. The information provided herein will facilitate efficient development and improvement of Pyropia quality by producing cultivars resistant to high temperature.

One-Step Bioconversion of Fatty Acids into C8–C9 Volatile Aroma Compounds by a Multifunctional Lipoxygenase Cloned from Pyropia haitanensis

The multifunctional lipoxygenase PhLOX cloned from Pyropia haitanensis was expressed in Escherichia coli with 24.4 mg·L-1 yield. PhLOX could catalyze the one-step bioconversion of C18-C22 fatty acids into C8-C9 volatile organic compounds (VOCs), displaying higher catalytic efficiency for eicosenoic and docosenoic acids than for octadecenoic acids. C20:5 was the most suitable substrate among the tested fatty acids. The C8-C9 VOCs were generated in good yields from fatty acids, e.g., 2E-nonenal from C20:4, and 2E,6Z-nonadienal from C20:5. Hydrolyzed oils were also tested as substrates. The reactions mainly generated 2E,4E-pentadienal, 2E-octenal, and 2E,4E-octadienal from hydrolyzed sunflower seed oil, corn oil, and fish oil, respectively. PhLOX showed good stability after storage at 4 °C for 2 weeks and broad tolerance to pH and temperature. These desirable properties of PhLOX make it a promising novel biocatalyst for the industrial production of volatile aroma compounds.