Large detection range and high strain sensitivity fiber SPR sensor based on wave structure.

To achieve a fiber strain sensor with a large detection range and high sensitivity, this paper proposes a wave structured fiber SPR strain sensor. When subjected to axial strain, the wave structured fiber is stretched axially, increasing the stretchability of the sensor and achieving a large detection range strain sensing. Meanwhile, axial strain reduces the longitudinal amplitude of the fiber wave structure, effectively changing the total reflection angle of the transmitted beam at the peak and valley (SPR incidence angle) to achieve high sensitivity SPR strain sensing. The experiment indicates that the strain detection range of the sensor can reach 0-1800µÎµ, with a maximum strain sensitivity of 36.25pm/µÎµ. The wave structured fiber SPR strain sensor designed in this article provides a new approach to improve the range and sensitivity of strain detection.

Spiral cone fiber SPR sensor for detecting ginsenoside Rg1.

The conical fiber SPR sensor is easy to manufacture and has been used in biochemical detection research, but it has the problem of structural fragility. This article proposes a spiral cone fiber SPR sensor, which introduces a spiral structure on the 76µm fiber coarse cone, achieving good coupling of the core mode into the cladding mode, and improving the physical strength and practicality of the cone-shaped fiber SPR sensor. By modifying the target protein on the surface of the sensor gold film, specific detection of ginsenoside Rg1, an active ingredient of traditional Chinese medicine ginseng, was achieved. The detection sensitivity was 0.138 nm/(µm/ml) and the detection limit was 0.22µm/ml. The proposed spiral cone fiber SPR sensor provides a new scheme for the specific detection of active ingredients in traditional Chinese medicine, which is structurally stable and physically strong.

High sensitivity fiber SPR sensor based on a spiral coarse cone structure.

A fiber SPR sensor can achieve rapid and portable detection of trivalent arsenic ions (As3+) in drinking water or food, but their sensitivity and detection limit need to be further improved and developed toward specific detection. This article proposed the implementation of the SPR sensor using a biased core fiber spiral coarse cone structure. The fine core of the biased core fiber was used to reduce the mode of transmitted light. By controlling the pitch of the spiral core to control the SPR incidence angle, a significant increase in the sensitivity of the fiber SPR sensor was achieved. Meanwhile, the harmless glutathione (GSH) was modified on the surface of the sensing gold film to achieve the specific detection of As3+. The experimental results indicate that the spiral coarse cone fiber SPR sensor proposed in this article has a detection sensitivity of 32.48 nm/ppb for As3+, with a detection limit as low as 0.011 ppb, meeting the detection requirements of the World Health Organization for As3+ in water, which provides a new feasible solution for fast, portable, and highly sensitive detection of metal ions in water and food.

Multi working mode SPR chip laboratory for high refractive index detection.

The Fiber SPR chip laboratory has become a popular choice in biochemical detection. To meet the needs of different kinds of analytes for the detection range and number of channels of the chip, we proposed a multi-mode SPR chip laboratory based on microstructure fiber in this paper. The chip laboratory was integrated with microfluidic devices made from PDMS and detection units made of bias three-core fiber and dumbbell fiber. By injecting light into different cores of a bias three-core fiber, different detection areas of dumbbell fiber can be selected, enabling the chip laboratory to enter high refractive index detection, multi-channel detection and other working modes. In the high refractive index detection mode, the chip can detect liquid samples with a refractive index range of 1.571-1.595. In multi-channel detection mode, the chip can achieve dual parameter detection of glucose and GHK-Cu, with sensitivities of 4.16 nm/(mg/mL) and 9.729 nm/(mg/mL), respectively. Additionally, the chip can switch to temperature compensation mode. The proposed multi working mode SPR chip laboratory, based on micro structured fiber, offers a new approach for the development of portable testing equipment that can detect multiple analytes and meet multiple requirements.

Three-dimensional micro displacement sensor based on fiber SPR mechanisms.

Three fiber micro displacement sensors can be combined to realize three-dimensional (3D) displacement sensing, but the system is complex. In this paper, a 3D displacement sensor based on fiber SPR was proposed, which was composed of displacement fiber and sensing fiber. By cascading the eccentric dual-core fiber and graded multimode fiber, the displacement fiber was realized. The V-groove was processed in the vertical and horizontal directions of the graded multimode fiber, and the inclined SPR sensing areas were fabricated to realize the sensing fiber. A straight beam from the middle core of the displacement fiber contacted the vertical V-groove inclined plane of the sensing fiber to realize the Y axis (up and down) direction micro displacement, contacted the horizontal V-groove inclined plane of the sensing fiber to realize the Z axis (front and back) direction micro displacement sensing. An oblique beam from the eccentric core of the displacement fiber cooperated with the sensing fiber to realize the micro displacement sensing in the X-axis (left and right) direction. The testing results indicate that the fiber SPR 3D micro displacement sensor can sense micro displacement in the X axis, Y axis and Z axis, and the wavelength sensitivity is 0.148 nm/µm, -3.724 nm/µm and 3.543 nm/µm, respectively. The light intensity sensitivity is -0.0014a.u./µm, -0.0458a.u./µm and -0.0494a.u./µm, respectively. When adjusting the parameters of eccentric dual-core fiber, the larger the core distance is, the greater the displacement sensitivity in the X-axis direction of the sensor is, and the smaller the detection range is. The proposed sensor can realize 3D micro displacement sensing by itself, which is expected to be used in the field of 3D micro displacement measurement and 3D space precision positioning.

Temperature-compensated fiber-optic SPR microfluidic sensor based on micro-nano 3D printing.

The current temperature-compensated fiber-optic surface plasmon resonance (SPR) biosensors are mainly open-ended outside the sensing structure, and there is a lack of temperature compensation schemes in fiber-optic microfluidic chips. In this paper, we proposed a temperature-compensated optical fiber SPR microfluidic sensor based on micro-nano 3D printing. Through the optical fiber micro-machining technology, the two sensing areas were designed on both sides of the same sensing fiber. The wavelength division multiplexing technology was used to collect the sensing light signals of the two sensing areas at the same time. The specific measurement of berberine and the detection of ambient temperature in the optical fiber SPR biological microfluidic channel were realized, and the temperature compensation matrix relationship was constructed, and then the temperature compensation was realized when measuring berberine biomolecules. Experiments have shown that the temperature sensitivity of the optical fiber SPR microfluidic sensor was 2.18 nm/°C, the sensitivity of the detection of berberine was 0.2646 nm/(µg/ml), the detection limit (LOD) was 0.38 µg/ml, and in a mixed solution showed an excellent specific detection impact.

High-sensitivity fiber SPR strain sensor based on n-type structure.

At present, fiber strain sensors are mainly of the grating type and interference type, while there is relatively little research on fiber surface plasmon resonance (SPR) strain sensors. In this Letter, we propose a highly sensitive fiber SPR strain sensor based on an n-type structure. The strain changes the shape of the fiber n-type structure, causing the transmission mode of light in the fiber to change, thereby changing the SPR incidence angle and causing the SPR resonance valley wavelength to shift, achieving highly sensitive SPR strain sensing. The test results indicate that the strain sensing sensitivity of the proposed sensor reaches 21.33 pm/µÎµ, and two n-type structures are connected in series to obtain a double n-type structure, further enhancing the strain sensing sensitivity to 33.44 pm/µÎµ. This fiber strain sensor has advantages of high sensitivity, low temperature cross talk, strong structural stability, and low production cost, and is expected to become a new solution for wearable intelligent monitoring equipment and strain sensors in the aerospace field.

Highly sensitive SPR curvature sensor based on graded-index fiber.

At present, fiber curvature sensors based on surface plasmon resonance (SPR) are mostly of the multimode fiber core type or cladding type. These types have many SPR modes, resulting that the sensitivity cannot be adjusted and is difficult to improve. In this Letter, a highly sensitive SPR curvature sensor based on graded-index fiber is proposed. The light-injecting fiber is eccentrically connected with the graded-index fiber to inject single-mode light. Due to the self-focusing effect, the light beam propagates in the graded-index multimode fiber with a cosine trajectory, and the cosine beam contacts the flat grooved sensing region fabricated on the graded-index fiber to generate SPR. Due to the single transmission mode of the proposed fiber SPR sensor, the curvature sensing sensitivity is greatly improved. By changing the light injection position of the graded-index multimode fiber, the sensitivity can be adjusted. The proposed curvature sensing probe has a high sensitivity and can identify the bending direction. When bending in the X direction, the sensitivity reaches 5.62 nm/m-1, and when bending in the - X direction, the sensitivity reaches 4.75 nm/m-1, which provides a new scheme for highly sensitive and directionally identifiable curvature measurement.

Single-cell RNA-seq of Lotus japonicus provide insights into identification and function of root cell types of legume.

The roots of legume plant play a crucial role in nitrogen fixation. However, the transcriptomes of different cell types of legume root and their functions remain largely unknown. Here, we performed single-cell RNA sequencing and profiled more than 22,000 single cells from root tips of Lotus japonicus, a model species of legume. We identified seven clusters corresponding to seven major cell types, which were validated by in situ hybridization. Further analysis revealed regulatory programs including phytohormone and nodulation associated with specific cell types, and revealed conserved and diverged features for the cell types. Our results represent the first single-cell resolution transcriptome for legume root tips and a valuable resource for studying the developmental and physiological functions of various cell types in legumes.

Expression, purification and structural characterization of resveratrol synthase from Polygonum cuspidatum.

Polygonum cuspidatum, an important medicinal plant in China, is a rich source of resveratrol compounds, and its synthesis related resveratrol synthase (RS) gene is highly expressed in stems. The sequence of the resveratrol synthase was amplified with specific primers. Sequence comparison showed that it was highly homologous to the STSs. The RS gene of Polygonum cuspidatum encodes 389 amino acids and has a theoretical molecular weight of 42.4 kDa, which is called PcRS1. To reveal the molecular basis of the synthesized resveratrol activity of PcRS1, we expressed the recombinant protein of full-length PcRS1 in Escherichia coli, and soluble protein products were produced. The collected products were purified by Ni-NTA chelation chromatography and appeared as a single band on SDS-PAGE. In order to obtain higher purity PcRS1, SEC was used to purify the protein and sharp single peak, and DLS detected that the aggregation state of protein molecules was homogeneous and stable. In order to verify the enzyme activity of the high-purity PcRS1, the reaction product was detected at 303 nm. By predicting the structural information of monomer PcRS1 and PcRS1 ligand complexes, we analyzed the ligand binding pocket and protein surface electrostatic potential of the complex, and compared it with the highly homologous STSs protein structures of the iso-ligand. New structural features of protein evolution are proposed. PcRS1 obtained a more complete configuration and the optimal orientation of the active site residues, thus improving its catalytic capacity in resveratrol synthesis.

The key regulator LcERF056 enhances salt tolerance by modulating reactive oxygen species-related genes in Lotus corniculatus.

BACKGROUND: The APETALA2/ethylene response factor (AP2/ERF) family are important regulatory factors involved in plants' response to environmental stimuli. However, their roles in salt tolerance in Lotus corniculatus remain unclear. RESULTS: Here, the key salt-responsive transcription factor LcERF056 was cloned and characterised. LcERF056 belonging to the B3-1 (IX) subfamily of ERFs was considerably upregulated by salt treatment. LcERF056-fused GFP was exclusively localised to nuclei. Furthermore, LcERF056- overexpression (OE) transgenic Arabidopsis and L. corniculatus lines exhibited significantly high tolerance to salt treatment compared with wild-type (WT) or RNA interference expression (RNAi) transgenic lines at the phenotypic and physiological levels. Transcriptome analysis of OE, RNAi, and WT lines showed that LcERF056 regulated the downstream genes involved in several metabolic pathways. Chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR) and yeast one-hybrid (Y1H) assay demonstrated that LcERF056 could bind to cis-element GCC box or DRE of reactive oxygen species (ROS)-related genes such as lipid-transfer protein, peroxidase and ribosomal protein. CONCLUSION: Our results suggested that the key regulator LcERF056 plays important roles in salt tolerance in L. corniculatus by modulating ROS-related genes. Therefore, it may be a useful target for engineering salt-tolerant L. corniculatus or other crops.

Genome-Wide Identification and Analysis of the Polycomb Group Family in Medicago truncatula.

Polycomb group (PcG) proteins, which are important epigenetic regulators, play essential roles in the regulatory networks involved in plant growth, development, and environmental stress responses. Currently, as far as we know, no comprehensive and systematic study has been carried out on the PcG family in Medicago truncatula. In the present study, we identified 64 PcG genes with distinct gene structures from the M. truncatula genome. All of the PcG genes were distributed unevenly over eight chromosomes, of which 26 genes underwent gene duplication. The prediction of protein interaction network indicated that 34 M. truncatula PcG proteins exhibited protein-protein interactions, and MtMSI1;4 and MtVRN2 had the largest number of protein-protein interactions. Based on phylogenetic analysis, we divided 375 PcG proteins from 27 species into three groups and nine subgroups. Group I and Group III were composed of five components from the PRC1 complex, and Group II was composed of four components from the PRC2 complex. Additionally, we found that seven PcG proteins in M. truncatula were closely related to the corresponding proteins of Cicer arietinum. Syntenic analysis revealed that PcG proteins had evolved more conservatively in dicots than in monocots. M. truncatula had the most collinearity relationships with Glycine max (36 genes), while collinearity with three monocots was rare (eight genes). The analysis of various types of expression data suggested that PcG genes were involved in the regulation and response process of M. truncatula in multiple developmental stages, in different tissues, and for various environmental stimuli. Meanwhile, many differentially expressed genes (DEGs) were identified in the RNA-seq data, which had potential research value in further studies on gene function verification. These findings provide novel and detailed information on the M. truncatula PcG family, and in the future it would be helpful to carry out related research on the PcG family in other legumes.

LNK1 and LNK2 Corepressors Interact with the MYB3 Transcription Factor in Phenylpropanoid Biosynthesis.

Subgroup 4 of R2R3-MYB transcription factors consists of four members, MYB3, MYB4, MYB7, and MYB32, which possess the conserved EAR repression motif (pdLHLD/LLxiG/S) in their C termini. Here, we show that MYB3 is a newly identified repressor in Arabidopsis (Arabidopsis thaliana) phenylpropanoid biosynthesis. However, the repression mechanism of MYB3 is completely different from MYB4, MYB7, and MYB32. Yeast two-hybrid screening using MYB3 as a bait isolates NIGHT LIGHT-INDUCIBLE AND CLOCK-REGULATED1 (LNK1) and LNK2, members of a small family of four LNK proteins. The repression activity of MYB3 to cinnamate 4-hydroxylase (C4H) gene expression is directly regulated by corepressors LNK1 and LNK2, which could facilitate binding of MYB3 with C4H promoter. The two conserved Asp residues in both region 1 and 2 domain of LNKs are essential to mediate protein-protein interaction. Importantly, the Extra N-terminal Tail domain plays a negative role in LNK-MYB3 transcription complex-dependent repression of the C4H gene. We conclude that LNK1 and LNK2 act as transcriptional corepressors necessary for expression of the phenylpropanoids biosynthesis gene C4H through recruitment to its promoter via interaction with MYB3.

Biosynthesis and regulation of cyanogenic glycoside production in forage plants.

The natural products cyanogenic glycosides (CNglcs) are present in various forage plant species including Sorghum spp., Trifolium spp., and Lotus spp. The release of toxic hydrogen cyanide (HCN) from endogenous CNglcs, which is known as cyanogenesis, leads to a serious problem for animal consumption while as defensive secondary metabolites, CNglcs play multiple roles in plant development and responses to adverse environment. Therefore, it is highly important to fully uncover the molecular mechanisms of CNglc biosynthesis and regulation to manipulate the contents of CNglcs in forage plants for fine-tuning the balance between defensive responses and food safety. This review summarizes recent studies on the production, function, polymorphism, and regulation of CNglcs in forage plants, aiming to provide updated knowledge on the ways to manipulate CNglcs for further beneficial economic effects.

FtSAD2 and FtJAZ1 regulate activity of the FtMYB11 transcription repressor of the phenylpropanoid pathway in Fagopyrum tataricum.

Little is known about the molecular mechanism of the R2R3-MYB transcriptional repressors involved in plant phenylpropanoid metabolism. Here, we describe one R2R3-type MYB repressor, FtMYB11 from Fagopyrum tataricum. It contains the SID-like motif GGDFNFDL and it is regulated by both the importin protein 'Sensitive to ABA and Drought 2' (SAD2) and the jasmonates signalling cascade repressor JAZ protein. Yeast two hybrid and bimolecular fluorescence complementation assays demonstrated that FtMYB11 interacts with SAD2 and FtJAZ1. Protoplast transactivation assays demonstrated that FtMYB11 acts synergistically with FtSAD2 or FtJAZ1 and directly represses its target genes via the MYB-core element AATAGTT. Changing the Asp122 residue to Asn in the SID-like motif results in cytoplasmic localization of FtMYB11 because of loss of interaction with SAD2, while changing the Asp126 residue to Asn results in the loss of interaction with FtJAZ1. Overexpression of FtMYB11or FtMYB11D126N in F. tataricum hairy roots resulted in reduced accumulation of rutin, while overexpression of FtMYB11D122N in hairy roots did not lead to such a change. The results indicate that FtMYB11 acts as a regulator via interacting with FtSAD2 or FtJAZ1 to repress phenylpropanoid biosynthesis, and this repression depends on two conserved Asp residues of its SID-like motif.

Changing a conserved amino acid in R2R3-MYB transcription repressors results in cytoplasmic accumulation and abolishes their repressive activity in Arabidopsis.

Sub-group 4 R2R3-type MYB transcription factors, including MYB3, MYB4, MYB7 and MYB32, act as repressors in phenylpropanoid metabolism. These proteins contain the conserved MYB domain and the ethylene-responsive element binding factor-associated amphiphilic repression (EAR) repression domain. Additionally, MYB4, MYB7 and MYB32 possess a putative zinc-finger domain and a conserved GY/FDFLGL motif in their C-termini. The protein 'sensitive to ABA and drought 2' (SAD2) recognizes the nuclear pore complex, which then transports the SAD2-MYB4 complex into the nucleus. Here, we show that the conserved GY/FDFLGL motif contributes to the interaction between MYB factors and SAD2. The Asp → Asn mutation in the GY/FDFLGL motif abolishes the interaction between MYB transcription factors and SAD2, and therefore they cannot be transported into the nucleus and cannot repress their target genes. We found that MYB4(D261N) loses the capacity to repress expression of the cinnamate 4-hydroxylase (C4H) gene and biosynthesis of sinapoyl malate. Our results indicate conservation among MYB transcription factors in terms of their interaction with SAD2. Therefore, the Asp → Asn mutation may be used to engineer transcription factors.

Production and transcriptional regulation of proanthocyanidin biosynthesis in forage legumes.

Proanthocyanidins (PA), also known as condensed tannins, contribute to important forage legumes traits including disease resistance and forage quality. PA in forage plants has both positive and negative effects on feed digestibility and animal performance. The analytical methods and their applicability in measuring the contents of PA in forage plants are essential to studies on their nutritional effects. In spite of important breakthroughs in our understanding of the PA biosynthesis, important questions still remain to be answered such as the PA polymerization and transport. Recent advances in the understanding of transcription factor-mediated gene regulation mechanisms in anthocyanin and PA biosynthetic pathway in model plants suggest new approaches for the metabolic engineering of PA in forage plants. The present review will attempt to present the state-of-the-art of research in these areas and provide an update on the production and metabolic engineering of PA in forage plants. We hope that this will contribute to a better understanding of the ways in which PA production to manipulate the content of PA for beneficial effects in forage plants.

Genome-wide analysis of AP2/ERF family genes from Lotus corniculatus shows LcERF054 enhances salt tolerance.

Lotus corniculatus is used in agriculture as a main forage plant. Members of the Apetala2/ethylene response factor (AP2/ERF) family play important roles in regulating gene expression in response to many forms of stress, including drought and salt. Here, starting from database of the L. corniculatus var. japonicus genome, we identified 127 AP2/ERF genes by insilico cloning method. The phylogeny, gene structures, and putative conserved motifs in L. corniculatus var. japonicus ERF proteins were analyzed. Based on the number of AP2/ERF domains and the function of the genes, 127 AP2/ERF genes from L. corniculatus var. japonicus were classified into five subfamilies named the AP2, dehydration-responsive element binding factor (DREB), ERF, RAV, and a soloist. Outside the AP2/ERF domain, many L. corniculatus var. japonicus-specific conserved motifs were detected. Expression profile analysis of AP2/ERF genes by quantitative real-time PCR revealed that 19 LcERF genes, including LcERF054 (KJ004728), were significantly induced by salt stress. The results showed that the LcERF054 gene encodes a nuclear transcription activator. Overexpression of LcERF054 in Arabidopsis enhanced the tolerances to salt stress, showed higher germination ratio of seeds, and had elevated levels of relative moisture contents, soluble sugars, proline, and lower levels of malondialdehyde under stress conditions compared to wild-type plants. The expression of hyperosmotic salinity response genes COR15A, LEA4-5, P5CS1, and RD29A was found to be elevated in the LcERF054-overexpressing Arabidopsis plants compared to wild type. These results revealed that the LcERF genes play important roles in L. corniculatus cv Leo under salt stress and that LcERFs are attractive engineering targets in applied efforts to improve abiotic stress tolerances in L. corniculatus cv Leo or other crops.

Comparative Genomics of Lotus japonicus Reveals Insights into Proanthocyanidin Accumulation and Abiotic Stress Response.

Lotus japonicus, is an important perennial model legume, has been widely used for studying biological processes such as symbiotic nitrogen fixation, proanthocyanidin (PA) biosynthesis, and abiotic stress response. High-quality L. japonicus genomes have been reported recently; however, the genetic basis of genes associated with specific characters including proanthocyanidin distribution in most tissues and tolerance to stress has not been systematically explored yet. Here, based on our previous high-quality L. japonicus genome assembly and annotation, we compared the L. japonicus MG-20 genome with those of other legume species. We revealed the expansive and specific gene families enriched in secondary metabolite biosynthesis and the detection of external stimuli. We suggested that increased copy numbers and transcription of PA-related genes contribute to PA accumulation in the stem, petiole, flower, pod, and seed coat of L. japonicus. Meanwhile, According to shared and unique transcription factors responding to five abiotic stresses, we revealed that MYB and AP2/ERF play more crucial roles in abiotic stresses. Our study provides new insights into the key agricultural traits of L. japonicus including PA biosynthesis and response to abiotic stress. This may provide valuable gene resources for legume forage abiotic stress resistance and nutrient improvement.

Wave type fiber SPR sensor for rapid and highly sensitive detection of hyperoside.

The fiber surface plasmon resonance (SPR) sensor used for the detection of active ingredients in traditional Chinese medicine has the problems of low sensitivity and difficult specific recognition. This paper proposed a wave type fiber SPR sensor, which reduced the mode of transmitted light through a periodic wave structure and caused concentrated and total reflection of the transmitted beam at the interface between the bent peak cladding and the air. A 50 nm gold film was coated on the surface of the cladding in the wave structure area to form the SPR sensing area. By controlling the width and height of the wave structure to control the total reflection angle of the transmitted light, i.e., the SPR incidence angle, the sensitivity of the fiber SPR sensor was effectively improved to 4972 nm/RIU. Furthermore, HSP90AA protein was modified on the gold film of the sensor to achieve specific detection of hyperoside. The longest single detection time was only 3 minutes, and the detection sensitivity was 0.53 nm/(µg/ml), with a detection limit as low as 0.68µg/ml, which is comparable to liquid chromatography. The proposed wave type fiber SPR sensor is fast in production and has high structural mechanical strength, providing a new approach for the rapid, highly sensitive, and specific detection of active ingredients in traditional Chinese medicine.