Sequential solvent induced phase transition extraction for profiling of endogenous phytohormones in plants by liquid chromatography-mass spectrometry

Determination of bisphenols in beeswax based on sugaring out-assisted liquid-liquid extraction: Method development and application in survey, recycling and degradation studies

The methodology of sugaring out-assisted liquid-liquid extraction (SULLE) coupled with high-performance liquid chromatography-fluorescence detection was devised for quantifying bisphenol A (BPA) and bisphenol B (BPB) in beeswax. The effectiveness of SULLE was methodically explored and proved superior to the salting out-assisted liquid-liquid extraction approach for beeswax sample preparation. The analytical performance underwent comprehensive validation, revealing detection limits of 10 μg/kg for BPA and 20 μg/kg for BPB. The method developed was employed to analyse commercial beeswax (n = 15), beeswax foundation (n = 15) and wild-build comb wax (n = 26) samples. The analysis revealed BPA presence in four commercial beeswax samples and three beeswax foundation samples, with the highest detected residue content being 88 ± 7 μg/kg. For BPB, two beeswax foundation samples were positive, with concentrations below the limits of quantification and 85 ± 4 μg/kg, respectively. No bisphenols were detected in wild-build comb wax. Furthermore, the bisphenol removal efficacy of two recycling methods-boiling in water and methanol extraction-was assessed. The findings indicated that after four recycling cycles using water boiling, 9.6% of BPA and 29.2% of BPB remained in the beeswax. Whereas methanol extraction resulted in approximately 7% residual after one recycling process. A long-term study over 210 days revealed the slow degradation of bisphenols in comb beeswax. This degradation fitted well with a first-order model, indicating half-lives (DT50) of 139 days for BPA and 151 days for BPB, respectively. This research provides the first report on bisphenol contamination in beeswax. The low removal rate during the recycling process and the gradual degradation in beeswax underscore the significance of bisphenol contamination and migration in bee hives along with their potential risk to pollinators warranting concern. Furthermore, the developed SULLE method shows promise in preparing beeswax samples to analyse other analytes.

Online micro solid phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry for trace analysis of endogenous plant hormones in Ulva linza

OBJECTIVE

Ulva linza (L.) is a species of green algae widely distributed in China. We aimed to establish a sensitive online analytical method for quantification of endogenous phytohormones in fresh minute seaweed samples.

METHOD

The method for quantification of endogenous plant hormones in fresh minute samples was developed based on a homemade online micro solid phase extraction (m-SPE) system coupled with an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) platform. The online m-SPE instrument injected the eluent of m-SPE directly onto the LC separation column, improving the utilization of samples and saving time. The m-SPE column, of which the effective size was 9.6 × 2 mm i.d., was filled with 19 mg of C18 (10 μm).

RESULTS

Under optimized conditions, the limits of detection were 0.002-0.060 ng ml^-1 for five plant hormones. The actual sample recoveries of phytohormones were 76.4-103.4% and the coefficients of variance were below 14.1%. The temporal distribution of these endogenous plant hormones of U. linza during different growth periods is described.

CONCLUSION

The proposed online m-SPE method was successfully applied to quantification of endogenous acidic and alkaline plant hormones in U. linza. It provides important information for the further study of the physiological and ecological effects of plant hormones in lower algal species.

Axenic in vitro cultivation and genome diploidization of the moss Vesicularia montagnei for horticulture utilization

Mosses are widely used in the establishment of greenery. However, little research has been conducted to choose a suitable species or improve their performance for this application. In our study, we examined Vesicularia montagnei (V. montagnei), a robust moss that is widely distributed in temperate, subtropical, and tropical Asia with varying environmental conditions. Axenic cultivation system of V. montagnei was developed on modified BCD medium, which enabled its propagation and multiplication in vitro. In this axenic cultivation environment, several diploid V. montagnei lines with enhancement of rhizoid system were generated through artificial induction of diploidization. Transcriptomic analysis revealed that several genes responsible for jasmonic acid (JA) biosynthesis and signaling showed significant higher expression levels in the diploid lines compared to the wild type. These results are consistent with the increasement of JA content in the diploid lines. Our establishment of the axenic cultivation method may provide useful information for further study of other Vesicularia species. The diploid V. montagnei lines with improved rhizoid system may hold promising potential for greenery applications. Additionally, our study sheds light on the biosynthesis and functions of JA in the early landed plants.

A 3D-printed analytical device seamlessly integrating sample treatment for electrochemical detection of IAA in Marchantia polymorpha

Because of the pivotal point of Marchantia polymorpha (M. polymorpha) in plant evolution, its auxin (mainly indole-3-acetic acid, IAA) levels could provide useful evidence for the study of the evolution of IAA. However, M. polymorpha could not be easily pretreated for electrochemical detection because they are at the entry level of land plants. Herein, we designed a three-dimensional (3D)-printed analytical device for seamless integration of sample treatment and electrochemical detection. Specifically, the electrochemical cell could be used as a mortar in which a tiny plant sample could be ground with a 3D-printed pestle, followed by mixing with the buffer solution under vibration for electrochemical detection of IAA with a disposable working electrode at the bottom of the cell. Using our strategy, the limits of quantification could reach 0.05 μmol L^-1 after optimization of parameters. We were able to demonstrate that IAA in different tissues of wild-type and mutant M. polymorpha could be successfully differentiated after they were treated with the 3D-printed analytical device. The obtained results were comparable to the samples blended with zirconium beads while the differences of IAA levels in different tissues of M. polymorpha agreed well with previous reports. This study suggested the potential of sample treatment integrated with electrochemical detection for analysis of IAA using the 3D printing techniques and their possible applications in the research of plants and other fields.

Orphan gene PpARDT positively involved in drought tolerance potentially by enhancing ABA response in Physcomitrium (Physcomitrella) patens

Almost all genomes have orphan genes, the majority of which are not functionally annotated. There is growing evidence showed that orphan genes may play important roles in the environmental stress response of Physcomitrium patens. We identified PpARDT (ABA-responsive drought tolerance) as a moss-specific and ABA-responsive orphan gene in P. patens. PpARDT is mainly expressed during the gametophytic stage of the life cycle, and the expression was induced by different abiotic stresses. A PpARDT knockout (Ppardt) mutant showed reduced dehydration-rehydration tolerance, and the phenotype could be rescued by exogenous ABA. Meanwhile, transgenic Arabidopsis lines exhibiting heterologous expression of PpARDT were more sensitive to exogenous ABA than wild-type (Col-0) plants and showed enhanced drought tolerance. These indicate that PpARDT confers drought tolerance among land plants potentially by enhancing ABA response. Further, we identified genes encoding abscisic acid receptor PYR/PYL family proteins, and ADP-ribosylation factors (Arf) as hub genes associated with the Ppardt phenotype. Given the lineage-specific characteristics of PpARDT, our results provide insights into the roles of orphan gene in shaping lineage-specific adaptation possibly by recruiting common pre-existed pathway components.

Menthol-assisted homogenous liquid-liquid microextraction for HPLC/UV determination of favipiravir as an antiviral for COVID-19 in human plasma

Favipiravir is a promising antiviral agent that has been recently approved for treatment of COVID-19 infection. In this study, a menthol-assisted homogenous liquid–liquid microextraction method has been developed for favipiravir determination in human plasma using HPLC/UV. The different factors that could affect the extraction efficiency were studied, including extractant type, extractant volume, menthol amount and vortex time. The optimum extraction efficiency was achieved using 300 µL of tetrahydrofuran, 30 mg of menthol and vortexing for 1 min before centrifuging the sample for 5 min at 3467g. Addition of menthol does not only induce phase separation, but also helps to form reverse micelles to facilitate extraction. The highly polar favipiravir molecules would be incorporated into the hydrophilic core of the formed reverse micelle to be extracted by the non-polar organic extractant. The method was validated according to the FDA bioanalytical method guidelines. The developed method was found linear in the concentration range of 0.1 to 100 µg/mL with a coefficient of determination of 0.9992. The method accuracy and precision were studied by calculating the recovery (%) and the relative standard deviation (%), respectively. The recovery (%) was in the range of 97.1–103.9%, while the RSD (%) values ranged between 2.03 and 8.15 %. The developed method was successfully applied in a bioequivalence study of Flupirava® 200 mg versus Avigan® 200 mg, after a single oral dose of favipiravir administered to healthy adult volunteers. The proposed method was simple, cheap, more eco-friendly and sufficiently sensitive for biomedical application.

Homogeneous liquid-liquid extraction as an alternative sample preparation technique for biomedical analysis

Liquid-liquid extraction is a widely used technique of sample preparation in biomedical analysis. In spite of the high pre-concentration capacities of liquid-liquid extraction, it suffers from a number of limitations including time and effort consumption, large organic solvent utilization, and poor performance in highly polar analytes. Homogeneous liquid-liquid extraction is an alternative sample preparation technique that overcomes some drawbacks of conventional liquid-liquid extraction, and allows employing greener organic solvents in sample treatment. In homogeneous liquid-liquid extraction, a homogeneous phase is formed between the aqueous sample and the water-miscible extractant, followed by chemically or physically induced phase separation. To form the homogeneous phase, aqueous samples are mixed with water-miscible organic solvents, water-immiscible solvents/cosolvents, surfactants, or smart polymers. Then, phase separation is induced chemically (adding salt, sugar, or buffer) or physically (changing temperature or pH). This mode is rapid, sustainable, and cost-effective in comparison with other sample preparation techniques. Moreover, homogeneous liquid-liquid extraction is more suitable for the extraction of delicate macromolecules such as enzymes, hormones, and proteins and it is more compatible with liquid chromatography with tandem mass spectrometry, which is a vital technique in metabolomics and proteomics. In this review, the principle, types, applications, automation, and technical aspects of homogeneous liquid-liquid extraction are discussed.

High-throughput subzero-temperature assisted homogenous liquid-liquid extraction for the fast sample preparation of multiple phenolic compounds in propolis

In the present study, a high-throughput homogenous liquid-liquid extraction method was developed for fast sample preparation of multiple phenolic compounds in propolis. This method was proposed based on cooling samples array in subzero temperature to induce phase separation of ACN-H₂O extractant. Due to the high-throughput ability, optimization of extraction parameters was rapidly achieved by using a 5 × 4 × 3 samples array. In addition, multiple arrays were investigated for evaluating the analytical performance of the high-throughput method, which indicated that limits of detection and quantification were ranged from 0.04 to 0.35 µg/mL and 0.12 to 1.05 µg/mL, respectively. Recoveries and precisions in inter-day high-throughput studies were in the range of 90.55-105.50% and 2.58-4.30%, respectively. Comparing with the conventional liquid extraction method, this ecofriendly high-throughput method presented remarkable advantages in reducing sample and chemical consumption, as well as saving labor and time cost. The proposed method might provide a valuable strategy for the design of high-throughput extraction procedures.

Quantitative Determination of AZD3264, a Selective Ikb-Kinase IKK2 Inhibitor, in Dog Plasma by Solvent-Induced Phase Transition Extraction Coupled with HPLC-MS/MS and its Application to Pharmacokinetic Study in Dogs

BACKGROUND

AZD3264 is a small molecule inhibitor of selective IkB-kinase IKK2 currently in preclinical development for the potential treatment of asthma and chronic pulmonary obstructive disorder.

OBJECTIVE

A method for the quantitative analysis of AZD3264 was established and optimized by using HPLC tandem mass spectrometry in dog plasma.

METHOD

Plasma samples were pretreated using a solvent-induced phase transition extraction method with a methanol solution of omeprazole as the internal standard. Chromatographic separation was performed using a Thermo Hypersil GOLD-C18 (50 mm × 4.6 mm, 3 μm) column with the temperature maintained at 25°C. Mobile phase consisted of 0.1% formic acid in water and acetonitrile in a gradient mode at a flow rate of 0.6 mL/min. Mass spectrometric detection was carried out in selected reaction monitoring mode with positive electrospray ionization, and the mass transitions of AZD3264 and omeprazole were m/z 442.1 → 425.0 and m/z 346.0 → 198.0, respectively.

RESULTS

The intra-batch accuracy was within 95.11-105.06% and the precision was within 6.50-9.98%. The inter-batch accuracy was within 96.83-102.80% with a precision of 7.62-9.50%. The selectivity, sensitivity, linearity, dilution linearity, extraction recovery and matrix effect, stability, and carry-over met all requirements of the guidelines for bioanalytical method validation. AZD3264 showed linear pharmacokinetic characteristics following intravenous administration to dogs at 0.3-2.7 mg/kg.

CONCLUSIONS

The developed and validated method was successfully employed in pharmacokinetic studies in dogs following intravenous administration at the doses of 0.3, 0.9, and 2.7 mg/kg.

HIGHLIGHTS

This was the first investigation of the in vivo pharmacokinetic characteristics of AZD3264 in dogs by LC-MS/MS with SIPTE method for plasma sample preparation.

Microfluidic Chip-Based Induced Phase Separation Extraction as a Fast and Efficient Miniaturized Sample Preparation Method

Induced phase separation extraction (IPSE) is an efficient sample clean-up technique that can replace liquid-liquid extraction (LLE). The purpose of this study was to miniaturize IPSE by carrying it out in a microfluidic chip. An IPSE chip was designed and evaluated for its ability to separate and purify samples on a microscale. The 5 × 2 cm chip was fed with a solution of polar to non-polar model compounds in acetonitrile-water (1:1). In the 100 µm wide and 40 µm deep microchannels, the sample solution was efficiently separated into two immiscible phases by adding a hydrophobic solvent as inducer. Analytes present in the sample solution each migrated to their own favorable phase upon phase separation. After optimization, extraction and fractionation were easily and efficiently achieved. The behavior of analytes with a pH-dependent partitioning could be influenced by adjusting the pH of the sample solution. Scutellaria baicalensis extract, used in Traditional Chinese Medicine (TCM), was successfully separated in aglycones and glycosides. In this microscale system, the sample and solvent consumption is reduced to microliters, while the time needed for the sample pretreatment is less than one minute. Additionally, the extraction efficiency can reach up to 98.8%, and emulsion formation is avoided.

Simultaneous determination of multiple phytohormones in tomato by ionic liquid-functionalized carbon fibers-based solid-phase microextraction coupled with liquid chromatography-mass spectrometry

Phytohormones are interrelated by synergistic or antagonistic crosstalk and play important roles in the regulation of plant growth and development. In order to understand the interaction between phytohormones in the plant physiological network, it is necessary to determine trace levels of multiple phytohormones simultaneously in a complex matrix. Here, we synthesized ionic liquids containing different functional groups and modified the surface of carbon fibers with them. Based on these carbon fibers-ionic liquid (CFs-IL) materials, a solid phase microextraction method was developed to enable the simultaneous extraction of phytohormones. The adsorption specificity of multiple phytohormones was studied by identifying the hydrophobic, electrostatic, and π-π interactions, as well as hydrogen bonds, which favor simultaneous extraction of the relevant acidic, alkaline and neutral phytohormones by improving compatibility. The proposed method, coupled with liquid chromatography-tandem mass spectrometry, was applied to the simultaneous determination of 13 acidic, alkaline and neutral phytohormones in tomato. The limits of quantification were found to be in the range of 0.32-54.05 ng mL^-1 and 4.6-185.8 pg mL^-1, respectively, when measured by QQQ and Q-TOF. All of the relative recoveries were in the range of 94.40-113.37% with RSDs ≤15.36% (n = 3) for spiked tomato samples. This method is expected to be widely applied to multiple phytohormones analysis for in-depth researches concerning the physiological networks of plants.

Simultaneous analysis of thirteen phytohormones in fruits and vegetables by SPE-HPLC-DAD

Determination of phytohormones have attracted increasing attentions in food safety field. In this study, an efficient and quantitative method was developed which can simultaneously determinate thirteen phytohormones in fruits and vegetables using solid phase extraction (SPE) combined with high performance liquid chromatography-diode array detection (HPLC-DAD). The samples were extracted with 80% methanol containing 0.5% (V/V) formic acid, and the extracts were then concentrated and purified using primary secondary amine (PSA) and C18 tandem dual SPE cartridges. The analytes were separated on a Waters XBridge™ C18 column and eluated utilizing a gradient elution program of water and methanol. Mean recoveries of the thirteen analytes varied from 74.69 to 92.40%, with relative standard deviations < 3.57%. The limits of detection and quantitation were 0.005-0.018 mg/kg and 0.02-0.10 mg/kg, respectively. The phytohormones in kiwi fruit, strawberry, bean sprout, and green pepper were detected using the above method, respectively. Only the IAA content of 0.14 mg/kg was detected for the strawberry from a supermarket, which was lower than the prescribed limit in food safety standards (0.2 mg/kg).

Determination of thirteen acidic phytohormones and their analogues in tea (Camellia sinensis) leaves using ultra high performance liquid chromatography tandem mass spectrometry

Trace plant hormones play an important role in tea growth, development and quick response to biotic and abiotic stresses. However, lack of a sensitive method limits the research on plant hormone regulation for tea quality and yields. Herein, a highly sensitive method was developed using ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) for profiling and quantification of 13 acidic phytohormones and their analogues, including auxins, abscisic acid and gibberellins in fresh tea leaves. After optimizing the different C18 columns and mobile phase systematically, an Agilent Eclipse Plus C18 column combined with the mobile phase A (acetonitrile) and B (water) was employed. Target acidic phytohormones were extracted using acidified methanol, and tea matrices were cleaned up by dispersive solid phase adsorbents of polyvinylpolypyrrolidone (PVPP) and graphitized carbon black (GCB) followed by polymer-based mixed-mode cation-exchange solid phase extraction. The method showed good linearity for all 13 analytes with regression coefficients (R²) > 0.998. Satisfactory recoveries of 12 analytes spiked with three levels ranged from 71.8% to 109.9%, while intra-day and inter-day precisions were below 20%. Limits of detection (LODs) and limits of quantitation (LODs) for 12 acidic phytohormones were 0.1-4.2 μg kg^-1 and 0.3-13.9 μg kg^-1, respectively. Finally, this method was firstly employed to analyze 13 analytes in fresh tea leaves (with the treatment of dormancy, light qualities, exogenous hormones and infestation of pests), highlighting its sufficient capability for rapid analysis of multiclass phytohormones in agriculture field.

Translocation of Drought-Responsive Proteins from the Chloroplasts

Some chloroplast proteins are known to serve as messengers to transmit retrograde signals from chloroplasts to the nuclei in response to environmental stresses. However, whether particular chloroplast proteins respond to drought stress and serve as messengers for retrograde signal transduction are unclear. Here, we used isobaric tags for relative and absolute quantitation (iTRAQ) to monitor the proteomic changes in tobacco (Nicotiana benthamiana) treated with drought stress/re-watering. We identified 3936 and 1087 differentially accumulated total leaf and chloroplast proteins, respectively, which were grouped into 16 categories. Among these, one particular category of proteins, that includes carbonic anhydrase 1 (CA1), exhibited a great decline in chloroplasts, but a remarkable increase in leaves under drought stress. The subcellular localizations of CA1 proteins from moss (Physcomitrella patens), Arabidopsis thaliana and rice (Oryza sativa) in P. patens protoplasts consistently showed that CA1 proteins gradually diminished within chloroplasts but increasingly accumulated in the cytosol under osmotic stress treatment, suggesting that they could be translocated from chloroplasts to the cytosol and act as a signal messenger from the chloroplast. Our results thus highlight the potential importance of chloroplast proteins in retrograde signaling pathways and provide a set of candidate proteins for further research.

Simultaneous biomonitoring of 15 organophosphate flame retardants metabolites in urine samples by solvent induced phase transition extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry

Organophosphate flame retardants and plasticizers (OPFRs) are widely additives in consumer products and building materials. They are frequently detected in environmental media, including indoor air, water, soil, and dust. To provide a low-cost and multi-target tool for monitoring individual exposure to OPFRs, a high-throughput method for simultaneous detection of 15 urinary OFPR metabolites was established using solvent induced phase transition extraction (SIPTE) technique for sample pretreatment and ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC-MS/MS) for target quantification. SIPTE is implemented by adding a hydrophobic solvent (methyl tert-butyl ether, used as the phase transition solution) to the homogeneous acetonitrile (ACN) aqueous solution for phase separation. Method performance was validated based on the evaluation indicators. The linear range of this present method was between 0.1 and 50 ng/mL for 15 urinary OPFR metabolites. The limits of detection (LODs) were from 0.012 to 0.25 ng/mL, and the spiked recoveries ranged of 71.3-117.6%, with corresponding relative standard deviations (RSDs) from 4.8 to 25.6%. Unlike most studies only focused on the determination of dialkyl and diaryl phosphate esters (DAPs), our analytical method also covered hydroxylated OPFRs metabolites (OH-OPFRs). Seven DAPs with detection frequencies (DF) more than 60% were detected in a small pilot study (n = 15). Besides, 4-hydroxy diphenyl phosphate (4-HO-DPHP) could be also detected in urine samples. Overall, this newly developed high-throughput analytical method could simultaneously determine 15 urinary OPFRs metabolites and screen these biomarkers of human exposure to OPFRs.

Physiological and Transcriptome Analyses Reveal Short-Term Responses and Formation of Memory Under Drought Stress in Rice

In some plants, exposure to stress can induce a memory response, which appears to play an important role in adaptation to recurrent stress environments. However, whether rice exhibits drought stress memory and the molecular mechanisms that might underlie this process have remained unclear. Here, we ensured that rice drought memory was established after cycles of mild drought and re-watering treatment, and studied gene expression by whole-transcriptome strand-specific RNA sequencing (ssRNA-seq). We detected 6,885 transcripts and 238 lncRNAs involved in the drought memory response, grouped into 16 distinct patterns. Notably, the identified genes of dosage memory generally did not respond to the initial drought treatment. Our results demonstrate that stress memory can be developed in rice under appropriate water deficient stress, and lncRNA, DNA methylation and endogenous phytohormones (especially abscisic acid) participate in rice short-term drought memory, possibly acting as memory factors to activate drought-related memory transcripts in pathways such as photosynthesis and proline biosynthesis, to respond to the subsequent stresses.

Comparison of the Partition Efficiencies of Multiple Phenolic Compounds Contained in Propolis in Different Modes of Acetonitrile⁻Water-Based Homogenous Liquid⁻Liquid Extraction

Homogeneous liquid–liquid extraction (HLLE) has attracted considerable interest in the sample preparation of multi-analyte analysis. In this study, HLLEs of multiple phenolic compounds in propolis, a polyphenol-enriched resinous substance collected by honeybees, were performed for improving the understanding of the differences in partition efficiencies in four acetonitrile–water-based HLLE methods, including salting-out assisted liquid–liquid extraction (SALLE), sugaring-out assisted liquid–liquid extraction (SULLE), hydrophobic-solvent assisted liquid–liquid extraction (HSLLE), and subzero-temperature assisted liquid–liquid extraction (STLLE). Phenolic compounds were separated in reversed-phase HPLC, and the partition efficiencies in different experimental conditions were evaluated. Results showed that less-polar phenolic compounds (kaempferol and caffeic acid phenethyl ester) were highly efficiently partitioned into the upper acetonitrile (ACN) phase in all four HLLE methods. For more-polar phenolic compounds (caffeic acid, p-coumaric acid, isoferulic acid, dimethoxycinnamic acid, and cinnamic acid), increasing the concentration of ACN in the ACN–H₂O mixture could dramatically improve the partition efficiency. Moreover, results indicated that NaCl-based SALLE, HSLLE, and STLLE with ACN concentrations of 50:50 (ACN:H₂O, v/v) could be used for the selective extraction of low-polarity phenolic compounds. MgSO₄-based SALLE in the 50:50 ACN–H₂O mixture (ACN:H₂O, v/v) and the NaCl-based SALLE, SULLE, and STLLE with ACN concentrations of 70:30 (ACN:H₂O, v/v) could be used as general extraction methods for multiple phenolic compounds.

PpSARK Regulates Moss Senescence and Salt Tolerance through ABA Related Pathway

Senescence-associated receptor-like kinase (SARK) family members in Arabidopsis, soybean, and rice are known to be positive regulators of leaf senescence. In the meantime, SARKs are extensively involved in stress response. However, their function and underlying molecular mechanism in stress responses in moss are not well known. Here, we investigated functional roles of SARK isolated from Physcomitrella patens (PpSARK) in salt stress response and senescence. PpSARK transcripts significantly accumulated under NaCl and abscisic acid (ABA) treatments, with higher expression in the moss gametophyte stage. Insertional gain-of-function mutants of PpSARK (PpSARKg) were more tolerant to salt stress and ABA than wild type (WT), whereas senescence of mutants was delayed during the protonema stage. Expression of stress-responsive genes in the ABA related pathway, such as PpABI3, PpABI5, PpPP2C, and PpLEA were significantly higher in PpSARKg and WT under salt stress conditions, suggesting that PpSARK might positively regulate salt tolerance via an ABA-related pathway. Endogenous ABA contents also increased 3-fold under salt stress conditions. These results indicate that PpSARK functions as a positive regulator in salt stress responses, while possibly functioning as a negative regulator in senescence in moss.

Trace analysis of multi-class phytohormones in Oryza sativa using different scan modes in high-resolution Orbitrap mass spectrometry: method validation, concentration levels, and screening in multiple accessions

Phytohormones are signaling and regulating metabolites involved in numerous plant processes, including growth, development, and responses to stress. Currently, the focus is on the analysis of multiple phytohormones in order to characterize crosstalk and hormone signaling networks. In this paper, representative phytohormones of the major classes are simultaneously determined in rice tissues by a generic solid-liquid extraction, followed by liquid chromatography and electrospray ionization high-resolution tandem mass spectrometry using a Q-Exactive™ instrument. After a thorough optimization of the sample preparation, the analytical method was fully validated toward the ultra-trace quantification of six a priori selected plant hormones using three scan modes of the quadrupole-Orbitrap instrument: full-scan high-resolution mass spectrometry, targeted single ion monitoring (t-SIM), and t-SIM followed by data-dependent tandem mass spectrometry. Overall, a similar quantitative performance was noticed for the different scan modes. The analytical method was successfully applied to measure basal phytohormone levels in six different rice accessions, comprising Oryza sativa ssp. japonica, indica, and Oryza glaberrima. Hormone concentrations were higher in shoots than in roots or at least similar. Except for a lower level of salicylic acid in shoots of O. glaberrima versus O. sativa, no other differences in hormone levels could be noticed that were dependent of the (sub)species assignment of the analyzed accessions. Making use of the benefits of full-scan high-resolution mass spectrometry, a first post-run suspect screening was performed, suggesting - based on accurate mass measurements and isotopic patterns - the possible presence of about 50 additional plant hormones in the rice tissues. Graphical abstract ᅟ.

Development of an improved sample preparation platform for acidic endogenous hormones in plant tissues using electromembrane extraction

Despite their importance in pivotal signaling pathways due to trace quantities and complex matrices, the analysis of plant hormones is a challenge. Here, to improve this issue, we present an electromembrane extraction technology combined with liquid chromatography-tandem mass spectrometry for determination of acidic plant hormones including jasmonic acid, abscisic acid, salicylic acid, benzoic acid, gibberellic acid and gibberellin A₄ in plant tissues. Factors influencing extraction efficiency, such as voltage, extraction time and stirring rate were optimized using a design of experiments. Analytical performance was evaluated in terms of specificity, linearity, limit of quantification, precision, accuracy, recovery and repeatability. The results showed good linearity (r² > 0.995), precision and acceptable accuracy. The limit of quantification ranged from 0.1 to 10 ng mL^-1, and the recoveries were 34.6-50.3%. The developed method was applied in citrus leaf samples, showing better clean-up efficiency, as well as higher sensitivity compared to a previous method using liquid-liquid extraction. Organic solvent consumption was minimized during the process, making it an appealing method. More noteworthy, electromembrane extraction has been scarcely applied to plant tissues, and this is the first time that major plant hormones were extracted using this technology, with high sensitivity and selectivity. Taken together, this work gives not only a novel sample preparation platform using an electric field for plant hormones, but also a good example of extracting complex plant tissues in a simple and effective way.

Zooming In on Plant Hormone Analysis: Tissue- and Cell-Specific Approaches

Plant hormones are a group of naturally occurring, low-abundance organic compounds that influence physiological processes in plants. Our knowledge of the distribution profiles of phytohormones in plant organs, tissues, and cells is still incomplete, but advances in mass spectrometry have enabled significant progress in tissue- and cell-type-specific analyses of phytohormones over the last decade. Mass spectrometry is able to simultaneously identify and quantify hormones and their related substances. Biosensors, on the other hand, offer continuous monitoring; can visualize local distributions and real-time quantification; and, in the case of genetically encoded biosensors, are noninvasive. Thus, biosensors offer additional, complementary technologies for determining temporal and spatial changes in phytohormone concentrations. In this review, we focus on recent advances in mass spectrometry-based quantification, describe monitoring systems based on biosensors, and discuss validations of the various methods before looking ahead at future developments for both approaches.

A rapid approach to investigate spatiotemporal distribution of phytohormones in rice

BACKGROUND

Phytohormones play crucial roles in almost all stages of plant growth and development. Accurate and simultaneous determination of multiple phytohormones enabled us to better understand the physiological functions and the regulatory networks of phytohormones. However, simultaneous determination of multiple phytohormones in plant is still a challenge due to their low concentrations, structural and chemical diversity, and complex matrix of plant tissues. Therefore, development of a simple and selective method for the simultaneous determination of multiple phytohormones is highly needed.

RESULTS

We developed a clean-up strategy for profiling of multiple phytohormones, which can overcome the challenge of structural and chemical diversity. By using a one-step dispersive solid-phase extraction (DSPE) combined with UPLC-MS/MS, 54 phytohormones including auxins, ABA, SA, JA, GAs and CKs were simultaneously analyzed from a single rice sample extract. Using the developed method, we investigated the spatiotemporal distribution of phytohormones in rice. The profiling of various tissues of rice at different growth stages revealed the complexity of metabolic regulation and allocations of phytohormone species.

CONCLUSION

A rapid one-step method was developed for the simultaneous analysis of six groups of phytohormones, including cytokinins, auxins, salicylic acid, jasmonates, abscisic acid and gibberellins in a single run, using UPLC-ESI-MS/MS. The proposed method was successfully applied to investigate spatiotemporal distribution of multiple phytohormones in rice. The spatiotemporal information obtained may be helpful for better understanding of phytohormones functions throughout life cycle of rice when integrated into transcriptome and other omics data.