Mitochondrial GPAT-derived LPA controls auxin-dependent embryonic and postembryonic development.

Membrane properties are emerging as important cues for the spatiotemporal regulation of hormone signaling. Lysophosphatidic acid (LPA) evokes multiple biological responses by activating G protein-coupled receptors in mammals. In this study, we demonstrated that LPA derived from the mitochondrial glycerol-3-phosphate acyltransferases GPAT1 and GPAT2 is a critical lipid-based cue for auxin-controlled embryogenesis and plant growth in Arabidopsis thaliana. LPA levels decreased, and the polarity of the auxin efflux carrier PIN-FORMED1 (PIN1) at the plasma membrane (PM) was defective in the gpat1 gpat2 mutant. As a consequence of distribution defects, instructive auxin gradients and embryonic and postembryonic development are severely compromised. Further cellular and genetic analyses revealed that LPA binds directly to PIN1, facilitating the vesicular trafficking of PIN1 and polar auxin transport. Our data support a model in which LPA provides a lipid landmark that specifies membrane identity and cell polarity, revealing an unrecognized aspect of phospholipid patterns connecting hormone signaling with development.

Edwardsiella tarda Attenuates Virulence upon Oxytetracycline Resistance.

The relationship between antibiotic resistance and bacterial virulence has not yet been fully explored. Here, we use Edwardsiella tarda as the research model to investigate the proteomic change upon oxytetracycline resistance (LTB4-ROTC). Compared to oxytetracycline-sensitive E. tarda (LTB4-S), LTB4-ROTC has 234 differentially expressed proteins, of which the abundance of 84 proteins is downregulated and 15 proteins are enriched to the Type III secretion system, Type VI secretion system, and flagellum pathways. Functional analysis confirms virulent phenotypes, including autoaggregation, biofilm formation, hemolysis, swimming, and swarming, are impaired in LTB4-ROTC. Furthermore, the in vivo bacterial challenge in both tilapia and zebrafish infection models suggests that the virulence of LTB4-ROTC is attenuated. Analysis of immune gene expression shows that LTB4-ROTC induces a stronger immune response in the spleen but a weaker response in the head kidney than that induced by LTB4-S, suggesting it's a potential vaccine candidate. Zebrafish and tilapia were challenged with a sublethal dose of LTB4-ROTC as a live vaccine followed by LTB4-S challenge. The relative percentage of survival of zebrafish is 60% and that of tilapia is 75% after vaccination. Thus, our study suggests that bacteria that acquire antibiotic resistance may attenuate virulence, which can be explored as a potential live vaccine to tackle bacterial infection in aquaculture.

Interspecies co-expression analysis of lateral root development using inducible systems in rice, Medicago, and Arabidopsis.

Lateral roots are crucial for plant growth and development, making them an important target for research aiming to improve crop yields and food security. However, their endogenous ontogeny and, as it were, stochastic appearance challenge their study. Lateral Root Inducible Systems (LRIS) can be used to overcome these challenges by inducing lateral roots massively and synchronously. The combination of LRISs with transcriptomic approaches significantly advanced our insights in the molecular control of lateral root formation, in particular for Arabidopsis. Despite this success, LRISs have been underutilized for other plant species or for lateral root developmental stages later than the initiation. In this study, we developed and/or adapted LRISs in rice, Medicago, and Arabidopsis to perform RNA-sequencing during time courses that cover different developmental stages of lateral root formation and primordium development. As such, our study provides three extensive datasets of gene expression profiles during lateral root development in three different plant species. The three LRISs are highly effective but timing and spatial distribution of lateral root induction vary among the species. Detailed characterization of the stages in time and space in the respective species enabled an interspecies co-expression analysis to identify conserved players involved in lateral root development, as illustrated for the AUX/IAA and LBD gene families. Overall, our results provide a valuable resource to identify potentially conserved regulatory mechanisms in lateral root development, and as such will contribute to a better understanding of the complex regulatory network underlying lateral root development.

CEPs suppress auxin signaling but promote cytokinin signaling to inhibit root growth in Arabidopsis.

C-terminally encoded peptides (CEPs) are peptide hormones that function as mobile signals coordinating crucial developmental programs in plants. Previous studies have revealed that CEPs exert negative regulation on root development through interaction with CEP receptors (CEPRs), CEP DOWNSTREAMs (CEPDs), the cytokinin receptor ARABIDOPSIS HISTIDINE KINASE (AHKs) and the transcriptional repressor Auxin/Indole-3-Acetic Acid (AUX/IAA). However, the precise molecular mechanisms underlying CEPs-mediated regulation of root development via auxin and cytokinin signaling pathways still necessitate further detailed investigation. In this study, we examined prior research and elucidated the underlying molecular mechanisms. The results showed that both synthetic AtCEPs and overexpression of AtCEP5 markedly supressed primary root elongation and lateral root (LR) formation in Arabidopsis. Molecular biology and genetics elucidated how CEPs inhibit root growth by suppressing auxin signaling while promoting cytokinin signaling. In summary, this study elucidated the inhibitory effects of AtCEPs on Arabidopsis root growth and provided insights into their potential molecular mechanisms, thus enhancing our comprehension of CEP-mediated regulation of plant growth and development.

Signal communication during microbial modulation of root system architecture.

Every living organism on Earth depends on its interactions with other organisms. In the rhizosphere, plants and microorganisms constantly exchange signals and influence each other's behavior. Recent studies have shown that many beneficial rhizosphere microbes can produce specific signaling molecules that affect plant root architecture and therefore could have substantial effects on above-ground growth. This review examines these chemical signals and summarizes their mechanisms of action, with the aim of enhancing our understanding of plant-microbe interactions and providing references for the comprehensive development and utilization of these active components in agricultural production. In addition, we highlight future research directions and challenges, such as searching for microbial signals to induce primary root development.

The beneficial rhizobacterium Bacillus velezensis SQR9 regulates plant nitrogen uptake via an endogenous signaling pathway.

Nitrogen fertilizer is widely used in agriculture to boost crop yields. Plant growth-promoting rhizobacteria (PGPRs) can increase plant nitrogen use efficiency through nitrogen fixation and organic nitrogen mineralization. However, it is not known whether they can activate plant nitrogen uptake. In this study, we investigated the effects of volatile compounds (VCs) emitted by the PGPR strain Bacillus velezensis SQR9 on plant nitrogen uptake. Strain SQR9 VCs promoted nitrogen accumulation in both rice and Arabidopsis. In addition, isotope labeling experiments showed that strain SQR9 VCs promoted the absorption of nitrate and ammonium. Several key nitrogen-uptake genes were up-regulated by strain SQR9 VCs, such as AtNRT2.1 in Arabidopsis and OsNAR2.1, OsNRT2.3a, and OsAMT1 family members in rice, and the deletion of these genes compromised the promoting effect of strain SQR9 VCs on plant nitrogen absorption. Furthermore, calcium and the transcription factor NIN-LIKE PROTEIN 7 play an important role in nitrate uptake promoted by strain SQR9 VCs. Taken together, our results indicate that PGPRs can promote nitrogen uptake through regulating plant endogenous signaling and nitrogen transport pathways.

Functional Proteomics Analysis of Norfloxacin-Resistant Edwardsiella tarda.

Multidrug-resistant Edwardsiella tarda threatens both sustainable aquaculture and human health, but the control measure is still lacking. In this study, we adopted functional proteomics to investigate the molecular mechanism underlying norfloxacin (NOR) resistance in E. tarda. We found that E. tarda had a global proteomic shift upon acquisition of NOR resistance, featured with increased expression of siderophore biosynthesis and Fe3+-hydroxamate transport. Thus, either inhibition of siderophore biosynthesis with salicyl-AMS or treatment with another antibiotic, kitasamycin (Kit), which was uptake through Fe3+-hydroxamate transport, enhanced NOR killing of NOR-resistant E. tarda both in vivo and in vitro. Moreover, the combination of NOR, salicyl-AMS, and Kit had the highest efficacy in promoting the killing effects of NOR than any drug alone. Such synergistic effect not only confirmed in vitro and in vivo bacterial killing assays but also applicable to other clinic E. tarda isolates. Thus, our data suggest a proteomic-based approach to identify potential targets to enhance antibiotic killing and propose an alternative way to control infection of multidrug-resistant E. tarda.

Alternative splicing of OsGS1;1 affects nitrogen-use efficiency, grain development, and amylose content in rice.

Excessive nitrogen fertilizer application is harmful to the environment and reduces the quality of cereal crops. Maintaining crop yields under low nitrogen (LN) conditions and improving quality are important goals for cereal crop breeding. Although the effects of nitrogen assimilation on crop nitrogen-use efficiency (NUE) have been intensively studied, natural variations of the key assimilation genes underlying grain development and quality are largely unclear. Here, we identified an NUE-associated gene, OsGS1;1, encoding glutamine synthase, through genome-wide association analysis, followed by validation experiments and functional analysis. Fifteen single-nucleotide polymorphisms in the OsGS1;1 region led to alternative splicing that generated two functional transcripts: OsGS1;1a and OsGS1;1b. The elite haplotype of OsGS1;1 showed high OsGS1;1b activity, which improved NUE, affected grain development, and reduced amylose content. The results show that OsGS1;1, which is induced under LN conditions, affects grain formation by regulating sugar metabolism and may provide a new avenue for the breeding of high-yield and high-quality rice (Oryza sativa).

RNA-seq analysis reveals an immunomodulatory peptide from highland barley activating RAW264.7 macrophages via TNF/NF-κB signaling pathway.

Highland barley (HB) is an important cereal crop distributed in the plateau region. Bioactive peptides (BAPs) derived from cereal proteins have shown biological functions. However, the knowledge of highland barley peptide (HBP) is limited. This study aims to explore the immunomodulatory activity of HBP and the relationship between immunomodulatory activity and related gene expression through RNA-seq. Firstly, HBP is isolated from protease hydrolysates of HB protein, yielding 12.04% of crude HB protein. The molecular weight of HBP is about 1702 Da analyzed by gel filtration chromatography, and HBP has a specific amino acid sequence as Gln-Pro-Gln-Gln-Pro-Phe-Pro-Gln (QPQPFPQ) analyzed by LC-MS. Besides, HBP contains 42.20% hydrophobic amino acids and 10.86% basic amino acids. Next, the immunomodulatory activity of HBP in vitro shows that HBP enhances the phagocytosis of RAW264.7 macrophages, promotes nitric oxide (NO) production and the mRNA expression of pro-inflammatory genes including tumor necrosis factor α (TNF-α), interleukin 1ß (IL-1ß), and inducible nitric oxide synthase (iNOS), and decreases the mRNA expression of anti-inflammatory gene, transforming growth factor ß1 (TGF-ß1). RNA-seq analysis reveals TNF and nuclear factor kappa B (NF-κB) pathways are upregulated, and RT-qPCR is performed to verify RNA-seq analysis. In conclusion, HBP activates RAW264.7 macrophages via TNF/NF-κB signaling pathway. HBP, as a significant immunomodulatory peptide, might be a promising resource for future functional foods.

The dynamic nature and regulation of the root clock.

Plants explore the soil by continuously expanding their root system, a process that depends on the production of lateral roots (LRs). Sites where LRs can be produced are specified in the primary root axis through a pre-patterning mechanism, determined by a biological clock that is coordinated by temporal signals and positional cues. This 'root clock' generates an oscillatory signal that is translated into a developmental cue to specify a set of founder cells for LR formation. In this Review, we summarize recent findings that shed light on the mechanisms underlying the oscillatory signal and discuss how a periodic signal contributes to the conversion of founder cells into LR primordia. We also provide an overview of the phases of the root clock that may be influenced by endogenous factors, such as the plant hormone auxin, and by exogenous environmental cues. Finally, we discuss additional aspects of the root-branching process that act independently of the root clock.

GH3-mediated auxin inactivation attenuates multiple stages of lateral root development.

Lateral root (LR) positioning and development rely on the dynamic interplay between auxin production, transport but also inactivation. Nonetheless, how the latter affects LR organogenesis remains largely uninvestigated. Here, we systematically analyze the impact of the major auxin inactivation pathway defined by GRETCHEN HAGEN3-type (GH3) auxin conjugating enzymes and DIOXYGENASE FOR AUXIN OXIDATION1 (DAO1) in all stages of LR development using reporters, genetics and inhibitors in Arabidopsis thaliana. Our data demonstrate that the gh3.1/2/3/4/5/6 hextuple (gh3hex) mutants display a higher LR density due to increased LR initiation and faster LR developmental progression, acting epistatically over dao1-1. Grafting and local inhibitor applications reveal that root and shoot GH3 activities control LR formation. The faster LR development in gh3hex is associated with GH3 expression domains in and around developing LRs. The increase in LR initiation is associated with accelerated auxin response oscillations coinciding with increases in apical meristem size and LR cap cell death rates. Our research reveals how GH3-mediated auxin inactivation attenuates LR development. Local GH3 expression in LR primordia attenuates development and emergence, whereas GH3 effects on pre-initiation stages are indirect, by modulating meristem activities that in turn coordinate root growth with LR spacing.

The rice transcription factor Nhd1 regulates root growth and nitrogen uptake by activating nitrogen transporters.

Plants adjust root architecture and nitrogen (N) transporter activity to meet the variable N demand, but their integrated regulatory mechanism remains unclear. We have previously reported that a floral factor in rice (Oryza sativa), N-mediated heading date-1 (Nhd1), regulates flowering time. Here, we show that Nhd1 can directly activate the transcription of the high-affinity ammonium (NH4+) transporter 1;3 (OsAMT1;3) and the dual affinity nitrate (NO3-) transporter 2.4 (OsNRT2.4). Knockout of Nhd1 inhibited root growth in the presence of NO3- or a low concentration of NH4+. Compared to the wild-type (WT), nhd1 and osamt1;3 mutants showed a similar decrease in root growth and N uptake under low NH4+ supply, while nhd1 and osnrt2.4 mutants showed comparable root inhibition and altered NO3- translocation in shoots. The defects of nhd1 mutants in NH4+ uptake and root growth response to various N supplies were restored by overexpression of OsAMT1;3 or OsNRT2.4. However, when grown in a paddy field with low N availability, nhd1 mutants accumulated more N and achieved a higher N uptake efficiency (NUpE) due to the delayed flowering time and prolonged growth period. Our findings reveal a molecular mechanism underlying the growth duration-dependent NUpE.

Metabolome analysis reveals the toxic effects of cadmium exposure on the egg sac of spider Pardosa pseudoannulata.

The investigation of the toxic effects of cadmium (Cd) on rice field invertebrates has attracted accumulating attention. Spider grants a novel insight into the impacts of Cd stress on invertebrates, but the effects of Cd-induced toxicity and molecular response mechanism of related metabolites in spider's egg sacs remain elusive. This investigation found that Cd stress distinctively decreased vitellogenin (Vg) content and hatched spiderlings numbers in the egg sac of Pardosa pseudoannulata. In addition, Cd stress exerted oxidative stress in the egg sac, manifested as the increase of superoxide dismutase and malondialdehyde levels. Further results showed that Cd exposure could affect egg sacs' energy metabolism, including protein and lipid contents. Metabolome analysis generated 73 up-regulated and 63 down-regulated differentially expressed metabolites (DEMs), mainly affecting phenylalanine metabolism, alpha-linolenic acid metabolism, pentose phosphate pathway, and biosynthesis of amino acids. Specifically, pathway analysis showed that Cd exposure down-regulated several key factors, including tyrosine, L-phenylalanine, O-phospho-L-serine, and L-cystathionine, and inhibited the metabolism of amino acids in the egg sacs. The subsequent correlation analysis found that three metabolite indicators, 9-Oxo-ODE, PG (17:0/18:2), and PE (17:0/20:5), were the dominant contributors to the egg sec's properties (i.e., Vg content and gained spiderlings). Collectively, this study hopes to provide valuable data for the protection of rice field spiders and offer novel perspectives for Cd pollution assessment and management.

Does Radiographic Alignment Correlate With Patient-Reported Functional Outcomes and Posttreatment Complications in Older Patients Treated for Wrist Fractures?

PURPOSE: Surgical treatment of distal radius fractures provides better fracture alignment than closed reduction; however, surgical treatment does not lead to better patient-reported function at 12 months. The aims of this study were to report the radiographic outcomes from the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, investigate the association between radiographic outcomes and patient-reported function, and explore whether this association was affected by posttreatment complications and direction of malalignment. METHODS: This study used the outcomes of the Combined Randomized and Observational Study of Surgery for Fractures In the distal Radius in the Elderly trial, which is a combined randomized and observational trial that compared volar-locking plate fixation with closed reduction and cast immobilization, to treat distal radius fractures in patients aged ≥60 years. Four radiographic outcomes (dorsal angulation, radial inclination, ulnar variance, and articular step) were reported at the following three time frames: (1) baseline, (2) after treatment, and (3) ≥6 weeks by treatment group. Secondary analysis was correlation of 12-month patient-reported function scores with 6-week radiographic measures for each of four radiographic parameters, and a subgroup analysis was conducted to investigate if this was affected by posttreatment complications. Tertiary analysis investigated if direction of malalignment affected the secondary analysis. RESULTS: We recruited 300 participants (166 randomized and 134 observational); 113 had volar-locking plate fixation, and 187 had closed reduction. There were no between-group differences for each of the four pretreatment radiographic parameters, but there were between-treatment group differences for all four radiographic parameters apart from articular step. We found no association between patient-reported function at 12 months and each of the four radiographic parameters at 6 weeks. This lack of association was unaffected by posttreatment complications and the direction of malalignment. CONCLUSIONS: For patients with wrist fractures aged ≥60 years, final radiographic alignment did not correlate with patient-reported function at 12 months. These findings were not affected by treatment type, and there was no association between radiographic alignment and posttreatment complications. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

Evaluating the Application Potential of a Recombinant Ganoderma Protein as Bioactive Ingredients in Cosmetics.

The aim of this study was to evaluate the application potential of a recombinant fungal immunomodulatory protein from Ganoderma lucidum (rFIP-glu). First, a recombinant plasmid pPIC9K::FIP-glu-His was transferred into Pichia pastoris for the production of protein. The protein was then to assess its free radical scavenging abilities and the effect on the viability of both human immortalized keratinocytes (HaCaT cells) and mouse B16-F10 melanoma cells (B16 cells) in vitro, followed by the effect on the melanin synthesis of B16 cells. The results of SDS-PAGE and western blot showed that rFIP-glu was successfully expressed. Furtherly, a bioactivity assay in vitro indicated that the scavenging rate of 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals reached 84.5% at 6.0 mg/mL (p ≤ 0.0001) of rFIP-glu, showing strong antioxidant activity. Subsequently, a safety evaluation demonstrated that rFIP-glu promoted the proliferation of HaCaT cells, with the cell viability reaching 124.3% at 48 µg/mL (p ≤ 0.01), regarding the cell viability of B16 cells after exposure to rFIP-glu (48 µg/mL) significantly inhibited, to 80.7% (p ≤ 0.01). Besides, rFIP-glu inhibited the melanin synthesis of B16 cells in a dose-dependent manner from 100-1000 µg/mL, and rFIP-glu at 500 µg/mL (p ≤ 0.01) exhibited the highest intracellular melanin amount reduction of 16.8%. Furthermore, a mechanism analysis showed that rFIP-glu inhibited tyrosinase (TYR) activity by up-regulating the expression of the microphthalmia-associated transcription factor (MITF) and down-regulating the gene expression of TYR and tyrosinase-related protein-1 (TYRP-1), thus inhibiting melanin synthesis. The data implied that rFIP-glu had significant antioxidant activity and whitening potency. It should be used as raw materials for cosmeceutical applications.

OsTUB1 confers salt insensitivity by interacting with Kinesin13A to stabilize microtubules and ion transporters in rice.

Salt stress is one of the major environmental factors limiting plant growth and development. Although microtubule (MT) organization is known to be involved in response to salt stress, few tubulin genes have been identified that confer salt insensitivity in plants. In this study, we identified a MT encoding gene, OsTUB1, that increased the survival rate of rice plants under salt stress by stabilizing MT organization and ion transporters. We found that OsTUB1 interacted with Kinesin13A protein, which was essential for OsTUB1-regulated MT organization under salt stress. Further molecular evidence revealed that a OsTUB1-Kinesin13A complex protected rice from salt stress by sustaining membrane-localized Na+ transporter OsHKT1;5, a key regulator of ionic homeostasis. Our results shed light on the function of tubulin and kinesin in regulating MT organization and stabilizing Na+ transporters and Na+ flux at the plasma membrane in rice. The identification of the OsTUB1-Kinesin13A complex provides novel genes for salt insensitivity rice breeding in areas with high soil salinity.

The volatile cedrene from Trichoderma guizhouense modulates Arabidopsis root development through auxin transport and signalling.

Rhizosphere microorganisms interact with plant roots by producing chemical signals that regulate root development. However, the distinct bioactive compounds and signal transduction pathways remain to be identified. Here, we showed that sesquiterpenes are the main volatile compounds produced by plant-beneficial Trichoderma guizhouense NJAU4742. Inhibition of sesquiterpene biosynthesis eliminated the promoting effect of this strain on root growth, indicating its involvement in plant-fungus cross-kingdom signalling. Sesquiterpene component analysis identified cedrene, a highly abundant sesquiterpene in strain NJAU4742, to stimulate plant growth and root development. Genetic analysis and auxin transport inhibition showed that the TIR1 and AFB2 auxin receptors, IAA14 auxin-responsive protein, and ARF7 and ARF19 transcription factors affected the response of lateral roots to cedrene. Moreover, the AUX1 auxin influx carrier and PIN2 efflux carrier were also found to be indispensable for cedrene-induced lateral root formation. Confocal imaging showed that cedrene affected the expression of pPIN2:PIN2:GFP and pPIN3:PIN3:GFP, which might be related to the effect of cedrene on root morphology. These results suggested that a novel sesquiterpene molecule from plant-beneficial T. guizhouense regulates plant root development through the transport and signalling of auxin.

Ammonium transporters cooperatively regulate rice crown root formation responding to ammonium nitrogen.

Crown roots (CRs) are major components of the rice root system. They form at the basal node of the shoot, and their development is greatly influenced by environmental factors. Ammonium nitrogen is known to impact plant root development through ammonium transporters (AMTs), but it remains unclear whether ammonium and AMTs play roles in rice CR formation. In this study, we revealed a significant role of ammonium, rather than nitrate, in regulating rice CR development. High ammonium supply increases CR formation but inhibits CR elongation. Genetic evidence showed that ammonium regulation of CR development relies on ammonium uptake mediated jointly by ammonium transporters OsAMT1;1, OsAMT1;2; OsAMT1;3, and OsAMT2;1, but not on root acidification which was the result of ammonium uptake. OsAMTs are also needed for glutamine-induced CR formation. Furthermore, we showed that polar auxin transport dependent on the PIN auxin efflux carriers acts downstream of ammonium uptake and assimilation to activate local auxin signaling at CR primordia, in turn promoting CR formation. Taken together, our results highlight a critical role for OsAMTs in cooperatively regulating CR formation through regulating auxin transport under nitrogen-rich conditions.

Phosphatidic Acid Directly Regulates PINOID-Dependent Phosphorylation and Activation of the PIN-FORMED2 Auxin Efflux Transporter in Response to Salt Stress.

Remodeling of auxin distribution during the integration of plant growth responses with the environment requires the precise control of auxin influx and efflux transporters. The plasma membrane-localized PIN-FORMED (PIN) proteins facilitate auxin efflux from cells, and their activity is regulated by reversible phosphorylation. How PIN modulates plant cellular responses to external stresses and whether its activity is coordinated by phospholipids remain unclear. Here, we reveal that, in Arabidopsis (Arabidopsis thaliana), the phosphatidic acid (PA)-regulated PINOID (PID) kinase is a crucial modulator of PIN2 activity and auxin redistribution in response to salt stress. Under salt stress, loss of phospholipase D function impaired auxin redistribution and resulted in markedly reduced primary root growth; these effects were reversed by exogenous PA. The phospholipase D-derived PA interacted with PID and increased PID-dependent phosphorylation of PIN2, which activated auxin efflux and altered auxin accumulation, promoting root growth when exposed to salt stress. Ablation of the PA binding motif not only diminished PID accumulation at the plasma membrane but also abolished PA-promoted PID phosphorylation of PIN2 and its function in coping with salt stress; however, this ablation did not affect inflorescence and cotyledon development or PIN2-dependent gravitropic and halotropic responses. Our data indicate a role for PA in coupling extracellular salt signaling to PID-directed PIN2 phosphorylation and polar auxin transport, highlighting the importance of lipid-protein interactions in the spatiotemporal regulation of auxin signaling.

Performance and complexity analysis using a sparse deep learning method for indoor terahertz transmission.

In this Letter, we propose and experimentally validate a sparse deep learning method (SDLM) for terahertz indoor wireless-over-fiber by transmitting a 16-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) signal over a 15-km single-mode fiber (SMF) and a wireless link distance of 60 cm at 135 GHz through a cost-effective intensity-modulated direct detection (IM-DD) communications system. The proposed SDLM imposes the L1-regularized mechanism on the cost function, which not only improves performance but also reduces complexity when compared with traditional Volterra nonlinear equalizer (VNLE), sparse VNLE, and conventional DLM. Our experimental findings show that the proposed SDLM provides viable options for successfully mitigating nonlinear distortions and outperforms conventional VNLE, conventional DLM, and SVNLE with a 76%, 72%, and 61% complexity reduction, respectively, for 8-QAM without losing signal integrity.