Recent developments and emerging trends of mass spectrometric methods in plant hormone analysis: a review

High-Performance Liquid Chromatographic Quantification of the Plant Hormone Abscisic Acid at ppb Levels in Plant Samples after a Single Immunoaffinity Column Cleanup

High-performance liquid chromatography with ultraviolet detection (HPLC-UV) is a common analysis technique due to its high versatility and simple operation. In the present study, HPLC-UV detection was integrated with immunoaffinity cleanup (IAC) of the sample extracts. The matrix effect was greatly reduced, and the limit of detection was as low as 1 ng/g of free abscisic acid (ABA) in fresh plant tissues. A monoclonal antibody 3F1 (mAb 3F1) was developed to specifically recognize free ABA but not ABA analogues. The mAb 3F1-immobilized immunoaffinity column exhibited a capacity of 850 ng/mL and an elution efficiency of 88.8-105% for standards. The extraction recoveries of the column for ABA ranged from 80.4 to 108.9%. ABA content was detected in various plant samples with IAC-HPLC-UV. The results were verified with ultraperformance liquid chromatography-electrospray tandem mass spectrometry. IAC-HPLC-UV can be a sensitive and cost-efficient method for plant hormone analysis.

The Cooperation Regulation of Antioxidative System and Hormone Contents on Physiological Responses of Wedelia trilobata and Wedelia chinensis under Simulated Drought Environment

Drought-induced metabolic dysregulation significantly enhances the production of reactive oxygen species (ROS), which, in turn, exerts a substantial influence on the oxidation-reduction regulatory status of cells. These ROS, under conditions of drought stress, become highly reactive entities capable of targeting various plant organelles, metabolites, and molecules. Consequently, disruption affects a wide array of metabolic pathways and eventually leads to the demise of the cells. Given this understanding, this study aimed to investigate the effects of different drought stress levels on the growth and development of the invasive weed Wedelia trilobata and its co-responding native counterpart Wedelia chinensis. Both plants evolved their defense mechanisms to increase their antioxidants and hormone contents to detoxify ROS to avoid oxidative damage. Still, the chlorophyll content fluctuated and increased in a polyethylene-glycol-simulated drought. The proline content also rose in the plants, but W. chinensis showed a significant negative correlation between proline and malondialdehyde in different plant parts. Thus, W. trilobata and W. chinensis exhibited diverse or unlike endogenous hormone regulation patterns under drought conditions. Meanwhile, W. trilobata and W. chinensis pointedly increased the content of indole acetic acid and gibberellic acid in a different drought stress environment. A positive correlation was found between endogenous hormones in other plant parts, including in the roots and leaves. Both simulated and natural drought conditions exerted a significant influence on both plant species, with W. trilobata displaying superior adaptation characterized by enhanced growth, bolstered antioxidant defense mechanisms, and heightened hormonal activities.

Highly sensitive analysis of photoregulation and dynamic distribution of phytohormones based on nanoconfined liquid phase nanoextraction

BACKGROUND

As a vital energy source, light is one of the most significant environmental signals for plants' growth and development. The crosstalk amongst phytohormones regulated by light exhibits quantitative dynamic changes, but methodologies to analyze their distribution during plant growth are still limited. Rapid, highly sensitive, low-invasive detection and simultaneous assessment of the levels of multiple classes of phytohormones have important phytology applications, however the existing sample pretreatment strategies remain intricate, laborious, and far from being developed for in vivo high-sensitivity testing. (81) RESULTS: We applied a nanoconfined liquid phase nanoextraction (NLPNE) technique based on acidified carbon nanofibers (ACNFs) in combination with LC-ESI-MS/MS for highly sensitive analysis of acidic phytohormones' photoregulation and dynamic distribution. In this system, the mass transfer ability of analytes entering the nanoconfined space is significantly improved given the nanoconfined effect. In particular, the accelerated and strong adsorption of alkaline compounds to the ACNFs surface provide minimum interference for acidic compounds (photosensitive phytohormones), which facilitates their simple, fast, and selective quantification with improved sensitivity. The ACNFs-NLPNE strategy achieved quantitative enrichment of multi-class phytohormones in less than 5 min, and detection limits down to 0.49 fg mL-1. Moreover, we monitored the phytohormone changes under red and blue monochromatic light with relative standard deviations <13.4 %. The results further indicated that short-time red light regulation promoted Lepidium sativum L. growth while blue light inhibited it. (141) SIGNIFICANCE: A nanoconfinement effect-based sample pretreatment platform was developed for monitoring photoregulation phytohormones dynamic distribution with higher sensitivity and stability. Our findings highlighted the importance of the NLPNE approach in providing an accurate plant crosstalk information at the molecular level, which opens a promising avenue for investigating internal hormonal responses to external stimuli. (52).

Harnessing Nature's Gifts: Salix nigra and Its Potential for Combating Hepatitis C Virus (HCV)

Hepatitis C virus (HCV) causes various liver complications, including fibrosis, cirrhosis, and steatosis, and finally progresses toward hepatocellular carcinoma (HCC). The current study aimed to explore the antiviral activity of the traditional Pakistani medicinal plant Salix nigra (S. nigra) known as black willow against the hepatitis C virus (HCV). The anti-HCV activity of S. nigra was established against stable Hep G2 cell lines expressing the HCV NS3 gene. Various plant-derived compounds with anti-HCV activity were identified, making phytotherapy a promising alternative to conventional treatments due to their cost-effectiveness and milder side effects. The two extraction methods (Maceration and Soxhlet) and four solvents (n-hexane, methanol, ethyl acetate, and water) were used to obtain crude extracts from S. nigra. Cytotoxicity testing showed that methanol (CC50 25 μg/mL) and water (CC50 30 μg/mL) extracts were highly toxic, while ethyl acetate and n-hexane (CC50 > 200 μg/mL) extracts were nontoxic at low concentrations (10-50 μg/mL), making them suitable for further anti-HCV investigations. Stable transfection of the NS3 gene was successfully performed in Hep G2 cells, creating a cellular expression system for studying virus-host interaction. The ethyl acetate extract of S. nigra exhibited significant inhibition of NS3 gene expression (mRNA and protein levels). The phytochemical analysis of S. nigra was also performed using the high-performance liquid chromatography (HPLC) technique. The phytochemical analysis identified several polyphenolic substances in the extracts of S. nigra. Our results concluded that the extracts of S. nigra have significantly reduced the expression of the NS3 gene at mRNA and protein levels. These findings contribute to the global efforts to combat hepatitis C by offering plant-based treatment options for HCV management.

Can plant hormonomics be built on simple analysis? A review

The field of plant hormonomics focuses on the qualitative and quantitative analysis of the hormone complement in plant samples, akin to other omics sciences. Plant hormones, alongside primary and secondary metabolites, govern vital processes throughout a plant's lifecycle. While active hormones have received significant attention, studying all related compounds provides valuable insights into internal processes. Conventional single-class plant hormone analysis employs thorough sample purification, short analysis and triple quadrupole tandem mass spectrometry. Conversely, comprehensive hormonomics analysis necessitates minimal purification, robust and efficient separation and better-performing mass spectrometry instruments. This review summarizes the current status of plant hormone analysis methods, focusing on sample preparation, advances in chromatographic separation and mass spectrometric detection, including a discussion on internal standard selection and the potential of derivatization. Moreover, current approaches for assessing the spatiotemporal distribution are evaluated. The review touches on the legitimacy of the term plant hormonomics by exploring the current status of methods and outlining possible future trends.

Expanded Coverage of Phytocompounds by Mass Spectrometry Imaging Using On-Tissue Chemical Derivatization by 4-APEBA

Probing the entirety of any species metabolome is an analytical grand challenge, especially on a cellular scale. Matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) is a common spatial metabolomics assay, but this technique has limited molecular coverage for several reasons. To expand the application space of spatial metabolomics, we developed an on-tissue chemical derivatization (OTCD) workflow using 4-APEBA for the confident identification of several dozen elusive phytocompounds. Overall, this new OTCD method enabled the annotation of roughly 280 metabolites, with only a 10% overlap in metabolic coverage when compared to analog negative ion mode MALDI-MSI on serial sections. We demonstrate that 4-APEBA outperforms other derivatization agents by providing: (1) broad specificity toward carbonyls, (2) low background, and (3) introduction of bromine isotopes. Notably, the latter two attributes also facilitate more confidence in our bioinformatics for data processing. The workflow detailed here trailblazes a path toward spatial hormonomics within plant samples, enhancing the detection of carboxylates, aldehydes, and plausibly other carbonyls. As such, several phytohormones, which have various roles within stress responses and cellular communication, can now be spatially profiled, as demonstrated in poplar root and soybean root nodule.

Metabolic profiles of 2-oxindole-3-acetyl-amino acid conjugates differ in various plant species

Auxins are a group of phytohormones that play a key role in plant growth and development, mainly presented by the major member of the family - indole-3-acetic acid (IAA). The levels of free IAA are regulated, in addition to de novo biosynthesis, by irreversible oxidative catabolism and reversible conjugation with sugars and amino acids. These conjugates, which serve as inactive storage forms of auxin and/or degradation intermediates, can also be oxidized to form 2-oxindole-3-acetyl-1-O-ß-d-glucose (oxIAA-glc) and oxIAA-amino acids (oxIAA-AAs). Until now, only oxIAA conjugates with aspartate and glutamate have been identified in plants. However, detailed information on the endogenous levels of these and other putative oxIAA-amino acid conjugates in various plant species and their spatial distribution is still not well understood but is finally getting more attention. Herein, we identified and characterized two novel naturally occurring auxin metabolites in plants, namely oxIAA-leucine (oxIAA-Leu) and oxIAA-phenylalanine (oxIAA-Phe). Subsequently, a new liquid chromatography-tandem mass spectrometry method was developed for the determination of a wide range of IAA metabolites. Using this methodology, the quantitative determination of IAA metabolites including newly characterized oxIAA conjugates in roots, shoots and cotyledons of four selected plant models - Arabidopsis thaliana, pea (Pisum sativum L.), wheat (Triticum aestivum L.) and maize (Zea mays L.) was performed to compare auxin metabolite profiles. The distribution of various groups of auxin metabolites differed notably among the studied species as well as their sections. For example, oxIAA-AA conjugates were the major metabolites found in pea, while oxIAA-glc dominated in Arabidopsis. We further compared IAA metabolite levels in plants harvested at different growth stages to monitor the dynamics of IAA metabolite profiles during early seedling development. In general, our results show a great diversity of auxin inactivation pathways among angiosperm plants. We believe that our findings will greatly contribute to a better understanding of IAA homeostasis.

Synthesis of spindle-like amino-modified Zn/Fe bimetallic metal-organic frameworks as sorbents for dispersive solid-phase extraction and preconcentration of phytohormoes in vegetable samples

Amino-modified Zn/Fe bimetallic metal-organic frameworks (NH₂-Zn/Fe-MIL-88) were synthesized using a one-step solvothermal method with FeCl₃·6H₂O and Zn(NO₃)₂·6H₂O as metal salts and 2-aminoterephthalic acid as organic ligand. The morphology of NH₂-Zn/Fe-MIL-88 can be regulated from octahedral-like to spindle-like with changing molar ratios of metal salts. Using NH₂-Zn/Fe-MIL-88 as sorbent, a dispersive solid-phase extraction with putting sorbents into sample solution to extract targets was developed to preconcentrate phytohormones in vegetables. To study the extraction efficiency, a series of NH₂-Zn/Fe-MIL-88s with varying molar ratios of metal salts were prepared. The results indicated that NH₂-Zn/Fe-MIL-88(1) presented the highest extraction efficiency (82.6 %-98.1 %) to phytohormones among all prepared NH₂-Zn/Fe-MIL-88(x). The limits of detection were calculated at 0.07-0.15 ng/mL. The adsorption isotherms and kinetic parameters of NH₂-Zn/Fe-MIL-88 for phytohormones were conformed to Langmuir and pseudo-second-order models. The NH₂-Zn/Fe-MIL-88 as sorbent combined with HPLC was applied to detect phytohormones in cucumber and tomato samples.

Genome-wide identification, expression analysis, and transcriptome analysis of the IAA gene family in Zoysia japonica

BACKGROUND

AUX/IAA is an essential signaling molecule and has great physiological importance in various plants, but its function in Zoysia japonica remains unknown.

METHODS AND RESULTS

Genome-wide identification and analysis of AUX/IAA genes used bioinformatics methods to investigate the ZjIAA genes' expression of exogenous IAA hydroponics treatment for 2 h by qRT-PCR, control and exogenous IAA treated zoysia were subjected to transcriptome sequencing. ZjIAAs were distributed across the 13 subfamilies by phylogenetic analysis with Oryza sativa and Arabidopsis thaliana. Multiple sequence alignment revealed that the majority of genes were non-canonical ZjIAAs with incomplete domain. The optimal growth concentration of the IAA hormone was 0.05 mM, and the qRT-PCR analysis revealed that eight ZjIAAs were differentially expressed, with seven genes considerably upregulating and one gene significantly downregulating. The result of transcriptome sequencing revealed that 515 differentially expressed genes (DEGs) were identified, with 344 upregulated genes and 171 downregulated genes. A total of 18 genes were annotated as involved in the plant hormone signal transduction pathway. And 8 ZjIAAs exhibited distinct expressions, 7 upregulated, and only one downregulated, according to the qRT-PCR study.

CONCLUSIONS

Genome-wide identification and analysis increased the understanding of the evolution and function of the IAA family in zoysia. DEGs of control and treatment with 0.05 mM exogenous IAA hormone were investigated by transcriptome sequencing. ZjIAAs had substantial variations in the expression of associated genes, with the majority of genes upregulated and 18 genes implicated in plant hormone signal transduction.

Plant Hormonomics: A Key Tool for Deep Physiological Phenotyping to Improve Crop Productivity

Agriculture is particularly vulnerable to climate change. To cope with the risks posed by climate-related stressors to agricultural production, global population growth, and changes in food preferences, it is imperative to develop new climate-smart crop varieties with increased yield and environmental resilience. Molecular genetics and genomic analyses have revealed that allelic variations in genes involved in phytohormone-mediated growth regulation have greatly improved productivity in major crops. Plant science has remarkably advanced our understanding of the molecular basis of various phytohormone-mediated events in plant life. These findings provide essential information for improving the productivity of crops growing in changing climates. In this review, we highlight the recent advances in plant hormonomics (multiple phytohormone profiling) and discuss its application to crop improvement. We present plant hormonomics as a key tool for deep physiological phenotyping, focusing on representative plant growth regulators associated with the improvement of crop productivity. Specifically, we review advanced methodologies in plant hormonomics, highlighting mass spectrometry- and nanosensor-based plant hormone profiling techniques. We also discuss the applications of plant hormonomics in crop improvement through breeding and agricultural management practices.

Preparation and Characterization of Methyl Jasmonate Microcapsules and Their Preserving Effects on Postharvest Potato Tuber

Potato tubers tend to sprout during long-term storage, resulting in quality deterioration and shortened shelf life. Restrictions on the use of chlorpropham, the major potato sprout suppressant, have led to a need to seek alternative methods. In this study, the effects of methyl jasmonate (MeJA) solutions and MeJA microcapsules on sprouting and other key quality attributes of the potato tuber were investigated. The results showed that the MeJA solution was most effective at 300 μmol L⁻¹ according to TOPSIS analysis. To prepare MeJA microcapsules, the optimal formulation is with 0.04% emulsifier, 2.5% sodium alginate, 0.5% chitosan and 3% CaCl₂. Compared to 300 μmol L⁻¹ MeJA solution, MeJA microcapsules consumed a lower dose of MeJA but demonstrated a better retaining effect on the overall quality attributes of potato tubers. MeJA microcapsules are promising agents for the preservation of postharvest potato tubers.

Effect of ion source polarity and dopants on the detection of auxin plant hormones by ion mobility-mass spectrometry

Ion mobility spectrometry (IMS) equipped with a corona discharge (CD) ion source was used for measurement of three auxin plant hormones including indole-3-acetic acid (IAA), indole-3-propionic acid (IPA), and indole-3-butyric acid (IBA). The measurements were performed in both positive and negative polarities of the CD ion source. Dopant gases NH₃, CCl₄, and CHBr₃ were used to modify the ionization mechanism. A time-of-flight mass spectrometer (TOFMS) orthogonal to the IMS cell was used for identification of the product ions. Density functional theory was used to rationalize formation of the ions, theoretically. The mixtures of the auxins were analyzed by CD-IMS. The separation performance depended on the ion polarity and the dopants. In the positive polarity without dopants, auxins were ionized via protonation and three distinguished peaks were observed. Application of NH₃ dopant resulted in two ionization channels, protonation, and NH₄⁺ attachment leading to peak overlapping. In the negative polarity, two ionization reactions were operative, via deprotonation and O₂^- attachment. The separation of the monomer peaks was not achieved while the peaks of anionic dimers [2 M-H]^- were separated well. The best LOD (4 ng) was obtained in negative polarity with CCl₄ dopant. Methylation (esterification) of IAA improved LODs by about one order.

Transcriptomics-Based Identification of Genes Related to Tapetum Degradation and Microspore Development in Lily

Lily is a popular and economically ornamental crop around the world. However, its high production of pollen grains causes serious problems to consumers, including allergies and staining of clothes. During anther development, the tapetum is a crucial step for pollen formation and microspore release. Therefore, it is important to understand the mechanism of tapetum degradation and microspore development in lily where free pollen contamination occurs. Here, we used the cut lily cultivar ‘Siberia’ to characterize the process of tapetum degradation through the use of cytology and transcriptomic methods. The cytological observation indicated that, as the lily buds developed from 4 cm (Lo 4 cm) to 8 cm (Lo 8 cm), the tapetum completed the degradation process and the microspores matured. Furthermore, by comparing the transcriptome profiling among three developmental stages (Lo 4 cm, Lo 6 cm and Lo 8 cm), we identified 27 differentially expressed genes. These 27 genes were classed into 4 groups by function, namely, cell division and expansion, cell-wall morphogenesis, transcription factors, LRR-RLK (leucine-rich repeat receptor-like kinases), plant hormone biosynthesis and transduction. Quantitative real-time PCR was performed as validation of the transcriptome data. These selected genes are candidate genes for the tapetum degradation and microspore development of lily and our work provides a theoretical basis for breeding new lily cultivars without pollen.

[Novel adsorption material for solid phase extraction in sample pretreatment of plant hormones]

植物激素在植物生长过程中具有重要作用,调节植物生长、发育及抗逆的各个过程。植物激素超微精准定量分析一直是植物生理学研究的瓶颈问题。植物激素的准确、高效检测目前大多是基于液相色谱-串联质谱联用技术。样品前处理是植物激素色谱-质谱分析中必不可少的一个步骤,直接影响后续检测方法的灵敏度和准确性。在植物激素各种前处理方法中,固相萃取(SPE)技术应用非常广泛。在萃取小柱基础上发展了多种新形式(分散固相萃取、磁性固相萃取、固相微萃取等,称之为SPE相关方法)。在上述SPE相关方法中,吸附材料的选择均是关键因素,决定了样品前处理过程的目标物提取、净化和富集效果。碳基材料(包括碳纳米管、石墨烯、碳氮化合物等)和有机骨架材料(包括金属有机骨架、共价有机材料)拥有结构可设计、比表面积大、稳定性良好等特性,非常适合作为吸附材料。分子印迹聚合物和超分子化合物依靠主-客体特异性分子识别作用,能显著提高样品前处理方法的选择性。本文重点针对植物激素样品前处理中的SPE技术,综述了近5年来上述几类功能化吸附材料的最新应用进展,并对其发展趋势进行展望。

Metabolomics for Crop Breeding: General Considerations

The development of new, more productive varieties of agricultural crops is becoming an increasingly difficult task. Modern approaches for the identification of beneficial alleles and their use in elite cultivars, such as quantitative trait loci (QTL) mapping and marker-assisted selection (MAS), are effective but insufficient for keeping pace with the improvement of wheat or other crops. Metabolomics is a powerful but underutilized approach that can assist crop breeding. In this review, basic methodological information is summarized, and the current strategies of applications of metabolomics related to crop breeding are explored using recent examples. We briefly describe classes of plant metabolites, cellular localization of metabolic pathways, and the strengths and weaknesses of the main metabolomics technique. Among the commercialized genetically modified crops, about 50 with altered metabolic enzyme activities have been identified in the International Service for the Acquisition of Agri-biotech Applications (ISAAA) database. These plants are reviewed as encouraging examples of the application of knowledge of biochemical pathways. Based on the recent examples of metabolomic studies, we discuss the performance of metabolic markers, the integration of metabolic and genomic data in metabolic QTLs (mQTLs) and metabolic genome-wide association studies (mGWAS). The elucidation of metabolic pathways and involved genes will help in crop breeding and the introgression of alleles of wild relatives in a more targeted manner.

Fluorescent biosensors illuminating plant hormone research

Phytohormones act as key regulators of plant growth that coordinate developmental and physiological processes across cells, tissues and organs. As such, their levels and distribution are highly dynamic owing to changes in their biosynthesis, transport, modification and degradation that occur over space and time. Fluorescent biosensors represent ideal tools to track these dynamics with high spatiotemporal resolution in a minimally invasive manner. Substantial progress has been made in generating a diverse set of hormone sensors with recent FRET biosensors for visualising hormone concentrations complementing information provided by transcriptional, translational and degron-based reporters. In this review, we provide an update on fluorescent biosensor designs, examine the key properties that constitute an ideal hormone biosensor, discuss the use of these sensors in conjunction with in vivo hormone perturbations and highlight the latest discoveries made using these tools.

Quantitative analysis of seven plant hormones in Lotus japonicus using standard addition method

Plant hormones have been identified to be versatile signaling molecules essential for plant growth, development, and stress response. Their content levels vary depending on the species, and they also change in response to any external stimuli. Thus, simultaneous quantification of multiple plant hormones is required to understand plant physiology. Sensitive and quantitative analysis using liquid chromatography-linked mass spectrometry (LC-MS/MS) has been used in detecting plant hormones; however, quantification without stable isotopes is yet to be established. In this study, we quantified seven representative plant hormones of Lotus japonicus, which is a model legume for standard addition method. Accurate masses for monoisotopic ions of seven phytohormones were determined for high-resolution mass spectrometry (HR-MS). Selected ion monitoring (SIM) mode based on accurate masses was used in detecting phytohormones in the roots, stems, and leaves. Evaluation of matrix effects showed ion suppression ranging from 10.2% to 87.3%. Both stable isotope dilution and standard addition methods were able to detect plant hormones in the roots, stems, and leaves, with no significant differences in using both approaches and thus a standard addition method can be used to quantify phytohormones in L. japonicus. The method will be effective, especially when stable isotopes are not available to correct for matrix effects.

Selective, sensitive, and miniaturized analytical method based on molecularly imprinted graphene oxide composites for the determination of naphthalene-derived plant growth regulators in apples

This paper reports a selective, sensitive, and miniaturized analytical method based on a molecularly imprinted graphene oxide (MIP-GO) composite as adsorbent for miniaturized tip solid-phase extraction (MTSPE) to determine naphthalene-derived plant growth regulators (PGRs) in apples. The proposed method combines the advantages of MIP-GOs (high selectivity), MTSPE (low consumption), and high-performance liquid chromatography-fluorescence detection (high sensitivity). Under optimized conditions, the method exhibited appreciable linearity (2.00-200 ng/g), low detection limits (0.21-0.53 ng/g), high accuracy (absolute recoveries: 87.6-99.5%), and high precision (relative standard deviations ≤ 3.0%), along with low consumption (0.5 mL sample solution and 2.0 mg adsorbent). In addition, the adsorption performance of the MIP-GO adsorbent did not decrease over ten months, highlighting the long storage and operational lifetime of the adsorbent. The proposed method was employed for the analysis of naphthalene-derived PGR residues in apples and exhibited promising potential for application in food safety analysis.

Hormones as go-betweens in plant microbiome assembly

The interaction of plants with complex microbial communities is the result of co-evolution over millions of years and contributed to plant transition and adaptation to land. The ability of plants to be an essential part of complex and highly dynamic ecosystems is dependent on their interaction with diverse microbial communities. Plant microbiota can support, and even enable, the diverse functions of plants and are crucial in sustaining plant fitness under often rapidly changing environments. The composition and diversity of microbiota differs between plant and soil compartments. It indicates that microbial communities in these compartments are not static but are adjusted by the environment as well as inter-microbial and plant-microbe communication. Hormones take a crucial role in contributing to the assembly of plant microbiomes, and plants and microbes often employ the same hormones with completely different intentions. Here, the function of hormones as go-betweens between plants and microbes to influence the shape of plant microbial communities is discussed. The versatility of plant and microbe-derived hormones essentially contributes to the creation of habitats that are the origin of diversity and, thus, multifunctionality of plants, their microbiota and ultimately ecosystems.

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.

Analytical methods in strigolactone research

Strigolactones (SLs) are important plant hormones that are produced via the carotenoid biosynthetic pathway and occur at extremely low concentrations in various plant species. They regulate root development, play important roles in symbioses between higher plants and mycorrhizal fungi, and stimulate germination of plant-parasitic Orobanche and Striga species. Chemical analysis is central to research on the biochemistry of SLs and their roles in developmental biology and plant physiology. Here we summarize key issues relating to the identification and quantification of SLs isolated from plant tissues and exudates. The advantages and drawbacks of different protocols used for strigolactone analysis are discussed, and guidelines for selecting a procedure that will minimize losses during isolation and purification prior to final analysis are proposed. Hyphenated techniques suitable for SL analysis such as GC-MS and LC-MS/MS are also discussed, and newer ambient techniques such as HR-DART-MS and DESI-MS are highlighted as tools with considerable potential in SL research. A key advantage of these methods is that they require only simply sample preparation.