Staying hungry: a roadmap to harnessing central regulators of symbiotic nitrogen fixation under fluctuating nitrogen availability.

Legumes have evolved specific inventions to enhance nitrogen (N) acquisition by establishing symbiotic interactions with N-fixing rhizobial bacteria. Because symbiotic N fixation is energetically costly, legumes have developed sophisticated mechanisms to ensure carbon-nitrogen balance, in a variable environment, both locally and at the whole plant level, by monitoring nodule number, nodule development, and nodular nitrogenase activity, as well as controlling nodule senescence. Studies of the autoregulation of nodulation and regulation of nodulation by nodule inception (NIN) and NIN-LIKE PROTEINs (NLPs) have provided great insights into the genetic mechanisms underlying the nitrate-induced regulation of root nodulation for adapting to N availability in the rhizosphere. However, many aspects of N-induced pleiotropic regulation remain to be fully explained, such as N-triggered senescence in mature nodules. Wang et al. determined that this process is governed by a transcriptional network regulated by NAC-type transcription factors. Characterization and dissection of these soybean nitrogen-associated NAPs (SNAPs) transcription factor-mastered networks have yielded a roadmap for exploring how legumes rewire nodule functions across a range of N levels, laying the foundation for enhancing the growth of N-deprived crops in agricultural settings.

A Novel Angle Segmentation Method for Magnetic Encoders Based on Filtering Window Adaptive Adjustment Using Improved Particle Swarm Optimization.

In this paper we outline newly-developed control algorithms, designed to achieve high-precision feedback for a motor control system using a magnetic encoder. The magnetic encoder, combing single-pole and multi-pole magnetic steels, was adopted to extend the resolution of the magnetic encoder. First, with a view to settling the issue of the jump points of the multi-pole angle value at the convergence of two adjacent magnetic poles, the angle segmentation method, which uses the window filter discrimination method, is employed to determine the actual angle value. The appropriate filter window width is selected via the improved particle swarm optimization (IPSO) algorithm, and an expanded resolution is achieved. Second, a compensation table is completed via a linear compensation algorithm based on virtual cutting to enhance the accuracy of the combined magnetic encoder. On this basis, a linear difference algorithm is used to achieve deviation correction of the angle. Finally, the jump points can be restrained effectively via the angle segmentation method. The resolution reaches 0.05°, and the accuracy is 0.045°.

Stabilization of membrane topologies by proteinaceous remorin scaffolds.

In plants, the topological organization of membranes has mainly been attributed to the cell wall and the cytoskeleton. Additionally, few proteins, such as plant-specific remorins have been shown to function as protein and lipid organizers. Root nodule symbiosis requires continuous membrane re-arrangements, with bacteria being finally released from infection threads into membrane-confined symbiosomes. We found that mutations in the symbiosis-specific SYMREM1 gene result in highly disorganized perimicrobial membranes. AlphaFold modelling and biochemical analyses reveal that SYMREM1 oligomerizes into antiparallel dimers and may form a higher-order membrane scaffolding structure. This was experimentally confirmed when expressing this and other remorins in wall-less protoplasts is sufficient where they significantly alter and stabilize de novo membrane topologies ranging from membrane blebs to long membrane tubes with a central actin filament. Reciprocally, mechanically induced membrane indentations were equally stabilized by SYMREM1. Taken together we describe a plant-specific mechanism that allows the stabilization of large-scale membrane conformations independent of the cell wall.

Transcellular progression of infection threads in Medicago truncatula roots is associated with locally confined cell wall modifications.

The root nodule symbiosis with its global impact on nitrogen fertilization of soils is characterized by an intracellular colonization of legume roots by rhizobia. Although the symbionts are initially taken up by morphologically adapted root hairs, rhizobia persistently progress within a membrane-confined infection thread through several root cortical and later nodular cell layers. Throughout this transcellular passaging, rhizobia have to repeatedly pass host plasma membranes and cell walls. Here, we investigated this essential process and describe the concerted action of one of the symbiosis-specific pectin methyl esterases (SyPME1) and the nodulation pectate lyase (NPL) at the infection thread and transcellular passage sites. Their coordinated function mediates spatially confined pectin alterations in the cell-cell interface that result in the establishment of an apoplastic compartment where bacteria are temporarily released into and taken up from the subjacent cell. This process allows successful intracellular progression of infection threads through the entire root cortical tissue.

Polysaccharide-rich fractions from Enteromorpha prolifera improve hepatic steatosis and gut barrier integrity in high-fat diet-induced obese mice linking to modulation of gut microbiota.

Polysaccharides from Enteromorpha prolifera (EP) possess important benefits in the management of obesity and associated metabolic diseases, but to date, the underlying mechanism linking this alleviative effect of EP to gut microbiota remains obscure. This study aimed to investigate the effects of EP in improving lipid metabolism disorders and intestinal barrier disruption in mice with high-fat diet (HFD), and its association with modulation of gut microbiota. C57BL/6 mice were fed a control diet or a HFD with or without 5% EP for 12 weeks. Factors related to lipid metabolism, insulin signaling and intestinal barrier integrity, as well as the involvement of gut microbiota and metabolites, were measured. EP supplementation reduced HFD-induced adiposity and mitigated insulin resistance, hepatic steatosis and elevation of serum lipopolysaccharides (LPS). HFD impaired intestinal barrier integrity while improved due to EP. Moreover, EP administration ameliorated HFD-induced gut dysbiosis, as revealed by the increased short-chain fatty acid (SCFA)-producing bacteria (e.g., Bacteroides, Parabacteroides, Alloprevotella, and Ruminococcus) and gut barrier-protective Akkermansia muciniphila and decreased endotoxin-producing bacteria (e.g., Desulfovibrionaceae and Bilophila), accompanied by enrichment in intestinal SCFA content and reduction in circulating LPS level. The change of dominant bacterial genera is significantly correlated with improved metabolic profiles and intestinal permeability induced by EP. In conclusion, our results indicate that EP can attenuate HFD-induced metabolic disorders along with restoration of gut barrier integrity and lowering of circulating endotoxin, and these improvements are associated with modulation of gut microbiota composition and related metabolites. These data deepen mechanistic understanding of the anti-obesity and metabolic improving effects of EP.

Formin-mediated bridging of cell wall, plasma membrane, and cytoskeleton in symbiotic infections of Medicago truncatula.

Legumes have maintained the ability to associate with rhizobia to sustain the nitrogen-fixing root nodule symbiosis (RNS). In Medicago truncatula, the Nod factor (NF)-dependent intracellular root colonization by Sinorhizobium meliloti initiates from young, growing root hairs. They form rhizobial traps by physically curling around the symbiont.1,2 Although alterations in root hair morphology like branching and swelling have been observed in other plants in response to drug treatments3 or genetic perturbations,4-6 full root hair curling represents a rather specific invention in legumes. The entrapment of the symbiont completes with its full enclosure in a structure called the "infection chamber" (IC),1,2,7,8 from which a tube-like membrane channel, the "infection thread" (IT), initiates.1,2,9 All steps of rhizobium-induced root hair alterations are aided by a tip-localized cytosolic calcium gradient,10,11 global actin re-arrangements, and dense subapical fine actin bundles that are required for the delivery of Golgi-derived vesicles to the root hair tip.7,12-14 Altered actin dynamics during early responses to NFs or rhizobia have mostly been shown in mutants that are affected in the actin-related SCAR/WAVE complex.15-18 Here, we identified a polarly localized SYMBIOTIC FORMIN 1 (SYFO1) to be required for NF-dependent alterations in membrane organization and symbiotic root hair responses. We demonstrate that SYFO1 mediates a continuum between the plasma membrane and the cell wall that is required for the onset of rhizobial infections.

Exosomal miR-103a-3p ameliorates lipopolysaccharide-induced immune response in BEAS-2B cells via NF-κB pathway by targeting transducin ß-like 1X related protein 1.

Abnormal immune response contributes to pathophysiology of pneumonia and is recognized as a main factor for high incidence rate in children. The association between exosomes and inflammation has been reported in diverse cell types and diseases. The current study focuses on exploring the effects of exosomal miR-103a-3p on lipopolysaccharide (LPS)-induced inflammation, and investigates the underlying mechanisms. We proved that miR-103a-3p was lowly expressed in blood samples of pneumonia patients and LPS-induced lung cells, and overexpression of miR-103a-3p weaken the LPS-induced inflammation. Using luciferase reporter assay and immunoprecipitation assay, we demonstrated that miR-103a-3p directly binds to a specific region of transducin ß-like 1X related protein 1 (TBL1XR1), mediating the NF-κB signalling pathway, thus regulating immune response. Taken together, our data revealed that miR-103a-3p functions as an anti-inflammatory gene in childhood pneumonia and can be applied as therapeutic targets for the treatment of childhood pneumonia in the future.

Smart Scanning Ion-Conductance Microscopy Imaging Technique Using Horizontal Fast Scanning Method.

To solve extended acquisition time issues inherent in the conventional hopping-scanning mode of scanning ion-conductance microscopy (SICM), a new transverse-fast scanning mode (TFSM) is proposed. Because the transverse motion in SICM is not the detection direction and therefore presents no collision problem, it has the ability to move at high speed. In TSFM, the SICM probe gradually descends in the vertical/detection direction and rapidly scans in the transverse/nondetection direction. Further, the highest point that decides the hopping height of each scanning line can be quickly obtained. In conventional hopping mode, however, the hopping height is artificially set without a priori knowledge and is typically very large. Consequently, TFSM greatly improves the scanning speed of the SICM imaging system by effectively reducing the hopping height of each pixel. This study verifies the feasibility of this novel scanning method via theoretical analysis and experimental study, and compares the speed and quality of the scanning images obtained in the TFSM with that of the conventional hopping mode. The experimental results indicate that the TFSM method has a faster scanning speed than other SICM scanning methods while maintaining the quality of the images. Therefore, TFSM provides the possibility to quickly obtain high-resolution three-dimensional topographical images of extremely complex samples.

Symbiotic root infections in Medicago truncatula require remorin-mediated receptor stabilization in membrane nanodomains.

Plant cell infection is tightly controlled by cell surface receptor-like kinases (RLKs). Like other RLKs, the Medicago truncatula entry receptor LYK3 laterally segregates into membrane nanodomains in a stimulus-dependent manner. Although nanodomain localization arises as a generic feature of plant membrane proteins, the molecular mechanisms underlying such dynamic transitions and their functional relevance have remained poorly understood. Here we demonstrate that actin and the flotillin protein FLOT4 form the primary and indispensable core of a specific nanodomain. Infection-dependent induction of the remorin protein and secondary molecular scaffold SYMREM1 results in subsequent recruitment of ligand-activated LYK3 and its stabilization within these membrane subcompartments. Reciprocally, the majority of this LYK3 receptor pool is destabilized at the plasma membrane and undergoes rapid endocytosis in symrem1 mutants on rhizobial inoculation, resulting in premature abortion of host cell infections. These data reveal that receptor recruitment into nanodomains is indispensable for their function during host cell infection.

Identification and characterization of a novel geminivirus with a monopartite genome infecting apple trees.

A novel circular DNA virus sequence has been identified through next-generation sequencing and in silico assembly of small RNAs of 21-24 nt from an apple tree grown in China. The virus genome was cloned using two independent approaches and sequenced. With a size of 2932 nt, it showed the same genomic structure and conserved origin of replication reported for members of the family Geminiviridae. However, the low nucleotide and amino acid sequence identity with known geminiviruses indicated that it was a novel virus, for which the provisional name apple geminivirus (AGV) is proposed. Rolling circle amplification followed by RFLP analyses indicated that AGV was a virus with a monopartite DNA genome. This result was in line with bioassays showing that the cloned viral genome was infectious in several herbaceous plants (Nicotiana bethamiana, Nicotiana glutinosa and Solanum lycopersicum), thus confirming it was complete and biologically active, although no symptoms were observed in these experimental hosts. AGV genome structure and phylogenetic analyses did not support the inclusion of this novel species in any of the established genera in the family Geminiviridae. A survey of 165 apple trees grown in four Chinese provinces showed a prevalence of 7.2% for AGV, confirming its presence in several cultivars and geographical areas in China, although no obvious relationship between virus infection and specific symptoms was found.

Differential distributions of mononucleotide repeat sequences in 256 viral genomes and its potential implications.

Mononucleotide repeats (MNRs) have been systematically investigated in the genomes of eukaryotic and prokaryotic organisms. However, detailed information on the distribution of MNRs in viral genomes is limited. In this study, we examined the distributions of MNRs in 256 fully sequenced virus genomes which showed extensive variations across viral genomes, and is significantly influenced by both genome size and CG content. Furthermore, the ratio of the observed to the expected number of MNRs (O/E ratio) appears to be influenced by both the host range and genome type of a particular virus. Additionally, the densities and frequencies of MNRs in genic regions are lower than in non-coding regions, suggesting that selective pressure acts on viral genomes. We also discuss the potential functional roles that these MNR loci could play in virus genomes. To our knowledge, this is the first analysis focusing on MNRs in viruses, and our study could have potential implications for a deeper understanding of virus genome stability and the co-evolution that occurs between a virus and its host.

A duplex, SYBR Green I-based RT-qPCR assay for the simultaneous detection of Apple chlorotic leaf spot virus and Cherry green ring mottle virus in peach.

BACKGROUND: Co-infections of Apple chlorotic leaf spot virus (ACLSV) and Cherry green ring mottle virus (CGRMV) in peach is common in China and have resulted in significant yield reductions. A reliable, sensitive and quantitive method is needed to detect and distinguish between ACLSV and CGRMV in peach. FINDINGS: We developed a sensitive and specific SYBR Green-I based RT-qPCR for the quantification of ACLSV and CGRMV in different peach tissues, and a duplex RT-qPCR system to detect ACLSV and CGRMV simultaneously. The RT-qPCR method was optimized using standard samples transcribed by the T7 Large Scale RNA Production System in vitro. The peach genes, RNA Polymerase subunit II (RPII) and Ubiquitin 10 (UBQ10), which were used as the internal controls for the quantification assay also showed good expression stability in this system. Single RT-qPCR assays showed that CGRMV in peach accumulates to a higher level than ACLSV. The detection limits of the duplex RT-qPCR assay were 10² and 104 copies for ACLSV and CGRMV, respectively. The sensitivity of the duplex RT-qPCR was as high as RT-qPCR and higher than RT-PCR. CONCLUSIONS: The SYBR Green-I RT-qPCR assay provided a sensitive, specific and reliable method for the detection and quantification of ACLSV and CGRMV in different peach tissues. The duplex RT-qPCR system provided a sensitive and specific method to detect and differentiate between ACLSV and CGRMV in a single sample. This RT-qPCR assay could be a useful tool for the routine diagnosis of these two viruses and for disease epidemiology studies in peach orchards.