Metalloid arsenic (As) is not a necessary element for plants, but its excessive accumulation is toxic to plants, and it also poses a great health risk to humans via the food chain.  Plants absorb and metabolize As through a variety of processes.  Arsenate in the form of As5+ is absorbed by phosphate transporters, but methylated As and As³⁺ enter plant tissues mainly through aquaporin channels.  Various strategies and practices have been proposed and applied to alleviate As toxicity or reduce As accumulation in plants, but an efficient and environment-friendly approach has yet to be developed.  This review comprehensively explores As sources and uptake mechanisms, as well as the interactions of phosphorus (P) and As in their uptake, transportation and influences on plant growth and physiological activities.  This comprehensive review covers the transport, metabolism, and tolerance processes that plants exhibit in response to As stress and the addition of P.  In addition, we also present recent advances in reducing As toxicity and accumulation by improving P nutrition, manipulating P transporter genes and optimizing the plant microbial community.  Finally, the future research directions and main challenges are briefly discussed.  

Maize root system plays a crucial role in the development of the aboveground plant and determines the yield through the uptake of water and nutrients in the field.  However, the genetic architecture of the maize root system is largely unknown mainly due to its complexity and the interactions between genotype and environment.  Using a high-throughput semi-automatic hydroponic platform with stable conditions, we comprehensively characterized the root system in a core population of 518 diverse inbred lines of maize.  Population structure analysis revealed that the panel has stratification and a linkage disequilibrium decay distance of less than 50 kb.  Based on genotyping with the high-density 600 K SNPs, we conducted a genome wide association analysis (GWAS) and identified nine SNPs and seven candidate genes significantly associated with 24 traits.  One candidate gene, GRMZM2G400533, is located at the upstream 5 kb region from the leading SNP (AX-91771718) and was significantly associated with primary root length and preferentially expressed in the primary root and crown root.  Expression of GRMZM2G400533 increased as the primary root developed but was negatively correlated with primary root elongation.  An analysis of candidate gene GRMZM2G400533 identified three functional variants and eight allelic haplotypes.  This study will broaden our understanding of maize root development and provide a theoretical basis for maize improvement through optimization of the root system.

Two cotton research institute (CRI) near-isogenic lines, CRI-12 glanded and CRI-12 glandless, were used to pinpoint potential genes and metabolic pathways linked to gossypol biosynthesis through transcriptome sequencing.  We discovered more than 235 million clean reads and 1,184 differentially expressed genes (DEGs).  Consecutively, we conducted a weighted gene co-expression network analysis and found a strong correlation between white and yellow modules containing GhTPS (GH_D09G0090) and GhCYP (GH_D05G2016) hub genes with the gossypol content.  Importance of the GhTPS and GhCYP genes was demonstrated using RT-qPCR, virus-induced gene silencing (VIGS), and target metabolite analysis.  Silencing these genes resulted in fewer glands on both leaves and stems two weeks after the infection compared to the wild type.  In addition, 152 metabolites were identified through targeted metabolite profiling.  Differential metabolite screening revealed 12 and 18 significantly different metabolites in TRV:GhTPS and TRV:GhCYP plants vs. the control group, respectively, showing a reduction in the accumulation of metabolites compared to the control.  Content of hemigossypol, the final product of gossypol biosynthesis, was also reduced, as revealed by target metabolite analysis, suggesting the role of these genes in the gossypol biosynthetic pathway.  Furthermore, a highly significant difference in gossypol content between the glanded and glandless lines was recorded.  Findings of this study reveal a strong link between the gossypol content and GhTPS and GhCYP hub genes, suggesting their role in the gossypol biosynthetic pathway to reduce the accumulation of hemigossypol, which may offer new comprehension into the regulatory checkpoints of the gossypol biosynthesis pathway in cotton.

Gossypium raimondii (2n=2x=26, D₅), an untapped wild species, is the putative progenitor of the D-subgenome of G. hirsutum (2n=4x=52, AD₁), an extensively cultivated species.  Here, we developed a G. hirsutum (recipient)–G. raimondii (donor) introgression population to exploit the favorable QTLs/genes and mapped potential quantitative trait loci (QTLs) from wild cotton species.  The introgression population consisted of 256 lines with an introgression rate of 52.33% for the G. raimondii genome.  The introgression segment length range was 0.03–19.12 Mb, with an average of 1.22 Mb.  The coverage of total introgression fragments from G. raimondii was 386.98 Mb.  Further genome-wide association analysis (Q+K+MLM) and QTL mapping (RSTEP-LRT) identified 59 common QTLs, including 14 stable QTLs and six common QTL (co-QTL) clusters, and one hotspot of micronaire (MIC).  The common QTLs for seed index all showed positive additive effects, while the common QTLs for boll weight all had negative additive effects, indicating that the linkage between seed index and boll weight could be broken.  QTLs for lint percentage showed positive effects and could be beneficial for improving cotton yield.  Most QTLs for fiber quality had negative additive effects, implying these QTLs were domesticated/improved in G. hirsutum.  A few fiber quality QTLs showed positive additive effects, so they could be used to improve cotton fiber quality.  The introgression lines developed could be useful for molecular marker-assisted breeding and mapping QTLs precisely for mining desirable genes from the wild species G. raimondii.  Such genes can improve cultivated cotton in the future through a design-breeding approach. 

The practice of conservation tillage or straw return to the farmland influences the grain yield and quality of rice (Oryza sativa).  The key volatile compound responsible for the fragrance of fragrant rice is 2-acetyl-1-pyrroline (2-AP), which is significantly affected by field management measures.  The purpose of this study was to investigate the impact of tillage management and straw return on the grain yield and biosynthesis of 2-AP in fragrant rice.  This study was conducted over two years in 2016 and 2017 and used two fragrant rice cultivars (Meixiangzhan 2 and Xiangyaxiangzhan) as materials.  The experimental design consisted of different tillage management and straw return treatments, which included three tillage management regimes: rotary tillage (T0), minimum tillage (T1), and no tillage (T2); and two straw return treatments: without straw return (S0) and straw return (S1).  The straw used for the experiment was sourced from the residue of the corresponding fragrant rice cultivar harvested in the early season.  Tillage management and straw return substantially affected the grain yields, grain quality, and 2-AP contents of both fragrant rice cultivars.  Compared with the T0S0 treatment, tillage management and straw return resulted in 2-AP content improvements in 2016 (12.41–116.85%) and 2017 (34.85–103.89%) on average.  Higher 2-AP contents were also detected in both fragrant rice cultivars in the T2S1 and T1S1 treatments.  A structural equation model (SEM) demonstrated that the activities of enzymes related to fragrance metabolism in the leaves and grain jointly regulated the biosynthesis of precursors of fragrance metabolism in the grain, which further promoted the accumulation of 2-AP.  In addition, a principal component analysis indicated that the T1S1 treatment was positively correlated with both 2-AP and grain yield.  The SEM demonstrated that the enzymes related to nitrogen metabolism, parameters related to photosynthesis, and yield components contributed to the grain yield.  The T1S1 treatment resulted in the highest average grain yield of 760.75 g m^–2, which could be attributed to increases in various attributes, such as the leaf area index, SPAD value, nitrogen metabolism, panicle number m^–2, and grain number per panicle.  In summary, the minimum tillage and straw return (T1S1) treatment is more effective at simultaneously improving both the grain yield and 2-AP content in fragrant rice.

Plant biomass is an important agronomic trait that has been subjected to intense human selection for yield improvement.  The underlying mechanism regulating biomass formation is currently gaining increasing attention, but it remains unexplored.  In this study, we isolated a cucumber (Cucumis sativus L.) minicuke mutant with remarkably reduced biomass.  The causative gene was identified as CsNMT1, a homologue of the Arabidopsis thaliana N-myristoyltransferase1.  Our clustered regularly interspaced shot palindromic repeat-based genome editing confirmed the key role of CsNMT1 in biomass regulation.  Multi-omics analyses integrating metabolomic and transcriptomic analyses revealed the suppression of a very early step of lignin biosynthesis and the corresponding down-regulation of genes involved in lignin biosynthesis in the minicikue mutant, suggesting an unexpected pathway for regulating biomass accumulation through lignin sink strength.  Our findings demonstrate the function of NMT1 in regulating plant biomass and its potential application value for biomass improvement in cucurbits.

Flowering is one of the most important phenological periods, as it determines the timing of fruit maturation and seed dispersal.  To date, both nitric oxide (NO) and DNA demethylation have been reported to regulate flowering in plants.  However, there is no compelling experimental evidence for a relationship between NO and DNA demethylation during plant flowering.  In this study, an NO donor and a DNA methylation inhibitor were used to investigate the involvement of DNA demethylation in NO-mediated tomato (Solanum lycopersicum cv. Micro-Tom) flowering.  The results showed that the promoting effect of NO on tomato flowering was dose-dependent, with the greatest positive effect observed at 10 μmol L^–1 of the NO donor S-nitrosoglutathione (GSNO).  Treatment with 50 μmol L^–1 of the DNA methylation inhibitor 5-azacitidine (5-AzaC) also significantly promoted tomato flowering.  Moreover, GSNO and 5-AzaC increased the peroxidase (POD) and catalase (CAT) activities and cytokinin (CTK) and proline contents, while they reduced the gibberellic acid (GA3) and indole-3-acetic acid (IAA) contents.  Co-treatment with GSNO and 5-AzaC accelerated the positive effects of GSNO and 5-AzaC in promoting tomato flowering.  Meanwhile, compared with a GSNO or 5-AzaC treatment alone, co-treatment with GSNO+5-AzaC significantly increased the global DNA demethylation levels in different tissues of tomato.  The results also indicate that DNA demethylation may be involved in NO-induced flowering.  The expression of flowering genes was significantly altered by the GSNO+5-AzaC treatment.  Five of these flowering induction genes, ARGONAUTE 4 (AGO4A), SlSP3D/SINGLE FLOWER TRUSS (SFT), MutS HOMOLOG 1 (MSH1), ZINC FINGER PROTEIN 2 (ZFP2), and FLOWERING LOCUS D (FLD), were selected as candidate genes for further study.  An McrBC-PCR analysis showed that DNA demethylation of the SFT gene in the apex and the FLD gene in the stem might be involved in NO-induced flowering.  Therefore, this study shows that NO might promote tomato flowering by mediating the DNA demethylation of flowering induction genes, and it provides direct evidence for a synergistic effect of NO and DNA demethylation in promoting tomato flowering.

Watermelon (Citrullus lanatus) is an economically important horticultural crop.  However, it is susceptible to low-temperature stress, which significantly challenges its production and supply.  Despite the great economic importance of watermelon, little is known about its response to low-temperature stress at the transcriptional level.  In this study, we performed a time-course transcriptome analysis to systematically investigate the regulatory network of watermelon under low-temperature stress.  Six low-temperature-responsive gene clusters representing six expression patterns were identified, revealing diverse regulation of metabolic pathways in watermelon under low-temperature stress.  Analysis of temporally specific differentially expressed genes revealed the time-dependent nature of the watermelon response to low temperature.  Moreover, ClMYB14 was found to be a negative regulator of low-temperature tolerance as ClMYB14-OE lines were more susceptible to low-temperature stress.  Co-expression network analysis demonstrated that ClMYB14 participates in the low-temperature response by regulating the unsaturated fatty acid pathway and heat shock transcription factor.  This study provides substantial information for understanding the regulatory network of watermelon in response to low-temperature stress, and identifies candidate genes for the genetic improvement of watermelon with higher low-temperature tolerance.

Pyrus pyrifolia, commonly known as sand pear, is a key economic fruit tree in temperate regions that possesses highly diverse germplasm resources for pear quality improvement.  However, research on the relationship between resistance and fruit quality traits in the breeding of fruit species like pear is limited.  Pan-transcriptomes effectively capture genetic information from coding regions and reflect variations in gene expression between individuals.  Here, we constructed a pan-transcriptome based on 506 samples from different tissues of sand pear, and explored the intrinsic relationships among phenotypes and the selection for disease resistance during improvement based on expression presence/absence variations (ePAVs).  The pan-transcriptome in this study contains 156,744 transcripts, among which the novel transcripts showed significant enrichment in the defense response.  Interestingly, disease resistance genes are highly expressed in landraces of pear but have been selected against during the improvement of this perennial tree species.  We found that the genetically diverse landraces can be divided into two subgroups and inferred that they have undergone different dispersal processes.  Through co-expression network analysis, we confirmed that the formation of stone cells in pears, the synthesis of fruit anthocyanins, and the ability to resist stress are interrelated.  They are jointly regulated by several modules, and the expression of regulatory genes has significant correlations with these three processes.  Moreover, we identified candidate genes such as HKL1 that may affect sugar content and are missing from the reference genome.  This study provides insights into the associations between complex fruit traits, while providing a database resource for pear disease resistance and fruit quality breeding.

UBL-UBA protein functions as a shuttle factor in the 26S ubiquitin degradation pathway, playing a critical role in plant growth and development, and responding to various biotic and abiotic stresses.  Although RAD23, a type of UBL-UBA protein, has been extensively studied in several plants, there is currently no comprehensive analysis available for kiwifruit (Actinidia chinensis).  In this study, we identified six AcRAD23 genes in kiwifruit and further analyzed their phylogenetic relationships, gene structure, conserved motif composition and cis-acting element in the promoter.  Subcellular localization experiments revealed that all AcRAD23 were localized in the nucleus and the cell membranes.  Quantitative real-time PCR (qRT-PCR) analysis demonstrated differential expression patterns of these AcRAD23 genes across different tissues and under various stress conditions (drought, waterlogging, salt stress, etc.), with AcRAD23D1 showing the highest responsiveness to abiotic stress.  Additionally, we investigated the biological function of AcRAD23D1 using VIGS-mediated gene silencing methods under drought stress conditions.  Suppression of AcRAD23D1 expression resulted in reduced relative water content (RWC) but increased malondialdehyde (MDA) content and relative electrolyte leakage (REL) levels in D1-VIGS lines compared to control lines.  Furthermore, D1-VIGS lines exhibited a higher accumulation of reactive oxygen species (ROS) along with decreased superoxide dismutase (SOD) and peroxidase (POD) enzyme activities.  These findings suggest that AcRAD23D1 may play a positive role in regulating kiwifruit’s response to drought stress.  Our results provide new insights into the potential involvement of AcRAD23 under abiotic stress conditions while offering a theoretical foundation for understanding the molecular mechanisms underlying kiwifruit’s adaptation to stresses. 

Xanthomonas oryzae pv. oryzae (Xoo) causes bacterial blight in rice, which reduces crop yield and leads to significant economic losses.  Bacterial sigma (σ) factors are highly specialized proteins that allow RNA polymerase to recognize and bind to specific promoters.  σ⁷⁰ factors also regulate the expression of genes involved in stress response and virulence.  However, the role of RpoD in Xoo is still unclear.  In this study, we found that σ⁷⁰ factor RpoD is quite conservative among phytopathogenic bacteria, especially in Xanthomonas sp.  In Xoo, PXO_RpoD plays an important role in oxidative stress tolerance and cell motility, as well as being essential for full virulence.  Cleavage under targets and tagmentation (CUT&Tag) analyses indicated that RpoD mediates the type three secretion system (T3SS) by regulating the regulation of hrpG and hrpX.  By performing bacterial one-hybrid and electrophoretic mobility assay (EMSA), we observed that RpoD directly bound to the promoters of hrpG and hrpX.  Collectively, these results demonstrate the transcriptional mechanism and pathogenic functions of RpoD in regulating cell motility and oxidative stress response, providing novel insights into potential targets for disease control.

Soybean cyst nematode (SCN, Heterodera glycines) is a devastating pathogen that infects soybean (Glycine max L. Merrill) and disrupts soybean production worldwide.  SCN infection upregulates or downregulates the expression of multiple genes in soybean.  However, the regulatory mechanisms that underlie these changes in gene expression remain largely unexplored.  N⁶-methyladenosine (m⁶A) methylation, one of the most prevalent mRNA modifications, contributes to transcriptional reprogramming during plant responses to pathogen infection.  Nevertheless, the role of m⁶A methylation in establishing compatible and incompatible soybean responses to SCN has not previously been studied.  Here, we performed transcriptome-wide m⁶A profiling of soybean roots infected with virulent and avirulent populations of SCN.  Compared with the compatible response, the incompatible response was associated with higher global m⁶A methylation levels, as well as more differentially modified m⁶A peaks (DMPs) and differentially expressed genes (DEGs).  A total of 133 and 194 genes showed significant differences in both transcriptional expression and m⁶A methylation levels in compatible and incompatible interactions; the most significantly enriched gene ontology terms associated with these genes were plant–pathogen interaction (compatible) and folate biosynthesis (incompatible).  Our findings demonstrate that the m⁶A methylation profiles of compatible and incompatible soybean responses are distinct and provide new insights into the regulatory mechanism underlying soybean response to SCN at the post-transcriptional modification level, which will be valuable for improving the SCN-resistant breeding.

Mating behavior is essential for sexual reproduction, and it is often modulated by key chemical cues.  In many moth species, males find compatible mates through the reception of sex pheromones which are released by females.  Pheromone receptors (PRs) are key elements in sensing these chemical signals.  Concurrently, male moths emit a complex blend of volatile compounds during courtship; however, the mechanisms for recognizing putative male pheromones remain poorly understood.  Here, we employed gas chromatography coupled with electroantennographic detection and mass spectrometry to analyze the volatile compounds produced by males of the cotton bollworm, Helicoverpa armigera.  Three candidate male sex pheromones were identified, with (Z)-7-dodecen-1-yl acetate (Z7-12:OAc) eliciting the most pronounced electrophysiological response in the male antenna.  The olfactory receptor neuron (ORN) ORN-a in Type A trichoid sensilla was shown to respond to Z7-12:OAc by conducting single sensillum recording (SSR) assays.  Additionally, we found that the OR13s from five Heliothinae species responded to Z7-12:OAc by using the Xenopus oocyte expression system and two-electrode voltage-clamp recording.  Our findings identified a candidate for evaluation in future behavioral studies of the poorly understood chemosensory recognition mechanisms underlying male sex pheromones.  If its relevance is supported by behavioral data, this knowledge may facilitate the design of novel olfactory regulators for effective pest control strategies involving mating disruption.

The ecdysone-induced transcription factor E93 in model insects plays multiple roles in the insect metamorphosis processes, such as remodeling larval tissues and determining adult tissue formation.  The knockdown of E93 in insects leads to incomplete metamorphosis, suggesting that E93 is a potential target for pest control.  In this study, the HaE93 gene in the cotton bollworm Helicoverpa armigera, a polyphagous pest of various commercial crops worldwide, was identified and found to have high expression in the egg, prepupal, and pupal stages.  The injection of dsHaE93 induced about 60% mortality in H. armigera at the larval-pupal stage.  About 30% survived but showed delayed pupation and abnormal wings, and the females developed reduced ovaries.  Therefore, about 90% of the HaE93 knockdown individuals failed to reproduce before they died.  The results of qRT-PCR showed that the expression levels of ecdysone primary-response genes, chitin synthesis-related genes, and wing and ovary development-related genes were reduced in HaE93 knockdown H. armigera.  These results indicated that HaE93 plays a critical role in larva-pupa-adult metamorphosis and the development of the cuticle, wing, and ovary in female H. armigera by regulating the expression of the associated genes.  Bioassays of dsHaE93 administered by either oral delivery or injection showed similar knockdown results, which suggested that HaE93 can be used as a target gene for the RNAi control of the pest H. armigera.

Genotyping by target sequencing (GBTS) integrates the advantages of silicon-based technology (high stability and reliability) and genotyping by sequencing (high flexibility and cost-effectiveness).  However, GBTS panels are not currently available in pigs.  In this study, based on GBTS technology, we first developed a 50K panel, including 52,000 single-nucleotide polymorphisms (SNPs), in pigs, designated GBTS50K.  A total of 6,032 individuals of Large White, Landrace, and Duroc pigs from 10 breeding farms were used to assess the newly developed GBTS50K.  Our results showed that GBTS50K obtained a high genotyping ability, the SNP and individual call rates of GBTS50K were 0.997–0.998, and the average consistency rate and genotyping correlation coefficient were 0.997 and 0.993, respectively, in replicate samples.  We also evaluated the efficiencies of GBTS50K in the application of population genetic structure analysis, selection signature detection, genome-wide association studies (GWAS), genotyped imputation, genetic selection (GS), etc.  The results indicate that GBTS50K is plausible and powerful in genetic analysis and molecular breeding.  For example, GBTS50K could gain higher accuracies than the current popular GGP-Porcine bead chip in genomic selection on 2 important traits of backfat thickness at 100 kg and days to 100 kg in pigs.  Particularly, due to the multiple SNPs (mSNPs), GBTS50K generated 100K qualified SNPs without increasing genotyping cost, and our results showed that the haplotype-based method can further improve the accuracies of genomic selection on growth and reproduction traits by 2 to 6%.  Our study showed that GBTS50K could be a powerful tool for underlying genetic architecture and molecular breeding in pigs, and it is also helpful for developing SNP panels for other farm animals.

Related to ABI3 and VP1 (RAV) transcription factors belong to the AP2 and B3 superfamily.  RAVs genes have been reported to be involved in plant growth and development regulation.  This study screened three RAV genes from Medicago truncatula and named one of them MtRAV1.  The MtRAV1 overexpressing plants exhibits traits such as plant dwarfing, delayed flowering, reduced leaf and floral organs, increased branching, and reduced pods and seeds.  Gene expression analysis results showed that overexpression of MtRAV1 inhibited the expression of Flowering Locus T (MtFTa1), Suppressor of Overexpression of CO 1 (MtSOC1), GA3-oxidase1 (MtGA3OX1), DWARF14 (MtD14) and Carotenoid Cleavage Dioxygenase 7 (MtCCD7).  To further investigate the regulation pathway involved by MtRAV1, RNA-sequencing (RNA-seq) and DNA affinity purification sequencing (DAP-seq) analysis were conducted.  RNA-seq results indicated that MtRAV1 might affect plant growth and development by regulating some genes in photosynthesis, circadian rhythm and plant hormone signaling pathways, especially the auxin signaling pathway.  Conjoint analysis of DAP-seq and RNA-seq revealed that MtRAV1 might inhibit the expression of Ferredoxin (MtFd-l3), Light-harvesting Chlorophyll a/b Binding Protein 1 (MtLhcb-l2) and Small Auxin Up-regulated RNA (MtSAUR-l), which related to photosystem II and auxin signaling pathway.  Summarily, MtRAV1 was preliminarily proven to be a key growth inhibitory factor in M. truncatula.

Toxin–antitoxin (TA) systems, which are prevalent in bacteria and archaea, play diverse roles in bacterial physiology and have been proposed to be significant in stress adaptation.  Despite the extensive characterization of numerous TA systems in various bacteria, the investigation of these systems within Streptococcus suis is still limited.  Here, we systematically analyzed the type II TA systems of 95 S. suis genomes available in the GenBank database using TAfinder.  A total of 612 putative type II TA systems were retrieved and classified into 10 categories by phylogenetic analysis.  Notably, an elevated occurrence of these TA systems was observed among the important prevalent serotypes 2, 4, 5, 9, 14, Chz, NCL1, and NCL3 strains.  The following study identified the activities of TA systems using 2 strategies and confirmed the regulatory effect of HigBA on the type VII secretion system in S. suis by measuring β-galactosidase activity and transcriptional changes.  Moreover, we unveiled a hitherto uncharacterized, highly prevalent novel TA system, with the composition of antitoxin–toxin–antitoxin (SS-ATA), which regulates the downstream two-component signaling system.  Altogether, this study systematically analyzed the type II TA systems within S. suis, highlighting the widespread distribution of HigBA and SS-ATA as important regulatory elements in S. suis.

Avian metapneumovirus (aMPV), a paramyxovirus, causes acute respiratory diseases in turkeys and swollen head syndrome in chickens.  This study established a reverse genetics system for aMPV subtype B LN16-A strain based on T7 RNA polymerase.  Full-length cDNA of the LN16-A strain was constructed by assembling 5 cDNA fragments between the T7 promoter and hepatitis delta virus ribozyme.  Transfection of this plasmid, along with the supporting plasmids encoding the N, P, M2-1, and L proteins of LN16-A into BSR-T7/5 cells, resulted in the recovery of aMPV subtype B.  To identify an effective insertion site, the enhanced green fluorescent protein (EGFP) gene was inserted into different sites of the LN16-A genome to generate recombinant LN16-As.  The results showed that the expression levels of EGFP at the site between the G and L genes of LN16-A were significantly higher than those at the other two sites (between the leader and N genes or replacing the SH gene).  To verify the availability of the site between G and L for foreign gene expression, the VP2 gene of very virulent infectious bursal disease virus (vvIBDV) was inserted into this site, and recombinant LN16-A (rLN16A-vvVP2) was successfully rescued.  Single immunization of specific-pathogen-free chickens with rLN16A-vvVP2 induced high levels of neutralizing antibodies and provided 100% protection against the virulent aMPV subtype B and vvIBDV.  Establishing a reverse genetics system here provides an important foundation for understanding aMPV pathogenesis and developing novel vector vaccines.

Crops produced using the practice of continuous cropping can become seriously damaged by plant-parasitic nematodes, an important indicator of continuous cropping obstacles.  As a typical and important perennial economic crop, dragon fruit is prone to serious plant-parasitic nematode infestation; however, whether it encounters continuous cropping obstacles remains unclear.  Here, we studied plant-parasitic nematodes (Meloidogyne spp. and Tylenchorhynchus sp.) in the soil and roots, soil nematode communities, metabolic footprint, soil integrated fertility, and the yield of intensively planted dragon fruit under non-continuous cropping (Y1) and 3 years (Y3) and 5 years (Y5) of continuous cropping, to determine potential continuous-cropping obstacles and factors that affect the yield of this fruit.  The largest numbers of plant-parasitic nematodes in the soil and roots were observed in Y5; the associated yield was reduced, and the dragon fruit was severely stressed.  Further analysis of the composition, diversity, and ecological function indices of soil nematodes showed that the soil ecological environment deteriorated after 3 years of continuous cropping, with Y5 having the worst results.  Similarly, the soil at Y5 had a significant inhibitory effect on the growth and reproduction of Caenorhabditis elegans.  Mantel test analysis and a random forest model showed that soil available phosphorus, soil exchange calcium, and soil nematode abundance and diversity were related significantly to yield.  Partial least squares path modeling revealed that soil fertility and soil nematode diversity directly impacts the yield of continuously cropped dragon fruit.  In summary, continuous cropping obstacles occurred in Y5 of intensive dragon fruit cultivation, with soil nematode diversity and soil fertility determining the crop’s yield.

Oxytetracycline (OTC) is used extensively in animal husbandry and enters the soil in different forms, causing severe environmental pollution.  Previous studies have shown that the genus Pseudomonas can potentially degrade antibiotics in the soil environment.  Environmental conditions, such as the initial concentration of antibiotics, incubation temperature and others, have significant impacts on the activity of antibiotic-degrading bacteria.  However, few reports have clarified the environmental impacts on the effectiveness of Pseudomonas spp.  In the present study, we investigated the effects of different initial concentrations of OTC and incubation temperatures, as well as soil sterilization, on OTC degradation by Pseudomonas strain T4.  We also focused on the microbial degradation pathways of OTC, and variations in both antibiotic resistance genes (ARGs) and microbial communities with T4 functioning under optimal conditions.  The results showed that the most effective degradation occurred under an initial OTC concentration of 2.5 mg kg^–1 at 30°C in unsterilized soil spiked with T4.  These conditions yielded an OTC degradation rate of 69.53% within 63 days.  The putative degradation pathways of OTC in the presence of T4 included dehydration, demethylation, deamination, hydroxylation, oxidation and ring opening.  Bacteroidetes, Proteobacteria and Acidobacteria played key roles in the biodegradation of OTC with T4 in the soil.  The results also showed that tet(G) was the most frequently detected ARGs among the 13 common tetracycline ARGs that were investigated.  The bacterial community shift observed in this study may provide new insights into the microbial degradation of OTC in soil.