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.

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.

Nitrogen (N) uptake is regulated by water availability, and a water deficit can limit crop N responses by reducing N uptake and utilization.  The complex and multifaceted interplay between water availability and the crop N response makes it difficult to predict and quantify the effect of water deficit on crop N status.  The nitrogen nutrition index (NNI) has been widely used to accurately diagnose crop N status and to evaluate the effectiveness of N application.  The decline of NNI under water-limiting conditions has been documented, although the underlying mechanism governing this decline is not fully understood.  This study aimed to elucidate the reason for the decline of NNI under water-limiting conditions and to provide insights into the accurate utilization of NNI for assessing crop N status under different water–N interaction treatments.  Rainout shelter experiments were conducted over three growing seasons from 2018 to 2021 under different N (75 and 225 kg N ha^–1, low N and high N) and water (120 to 510 mm, W0 to W3) co-limitation treatments.  Plant N accumulation, shoot biomass (SB), plant N concentration (%N), soil nitrate-N content, actual evapotranspiration (ET_a), and yield were recorded at the stem elongation, booting, anthesis and grain filling stages.  Compared to W0, W1 to W3 treatments exhibited NNI values that were greater by 10.2 to 20.5%, 12.6 to 24.8%, 14 to 24.8%, and 16.8 to 24.8% at stem elongation, booting, anthesis, and grain filling, respectively, across the 2018–2021 seasons.  This decline in NNI under water-limiting conditions stemmed from two main factors.  First, reduced ET_a and SB led to a greater critical N concentration (%N_c) under water-limiting conditions, which contributed to the decline in NNI primarily under high N conditions.  Second, changes in plant %N played a more significant role under low N conditions.  Plant N accumulation exhibited a positive allometric relationship with SB and a negative relationship with soil nitrate-N content under water-limiting conditions, indicating co-regulation by SB and the soil nitrate-N content.  However, this regulation was influenced by water availability.  Plant N accumulation sourced from the soil nitrate-N content reflects soil N availability.  Greater soil water availability facilitated greater absorption of soil nitrate-N into the plants, leading to a positive correlation between plant N accumulation and ET_a across the different water–N interaction treatments.  Therefore, considering the impact of soil water availability is crucial when assessing soil N availability under water-limiting conditions.  The findings of this study provide valuable insights into the factors contributing to the decline in NNI among different water–N interaction treatments and can contribute to the more accurate utilization of NNI for assessing winter wheat N status.

Avian metapneumovirus (aMPV) is a highly contagious pathogen that causes acute upper respiratory tract diseases in chickens and turkeys, resulting in serious economic losses.  Subtype B aMPV has recently become the dominant epidemic strain in China.  We developed an attenuated aMPV subtype B strain by serial passaging in Vero cells and evaluated its safety and efficacy as a vaccine candidate.  The safety test showed that after the 30th passage, the LN16-A strain was fully attenuated, as clinical signs of infection and histological lesions were absent after inoculation.  The LN16-A strain did not revert to a virulent strain after five serial passages in chickens.  The genomic sequence of LN16-A differed from that of the parent wild-type LN16 (wtLN16) strain and had nine amino acid mutations.  In chickens, a single immunization with LN16-A induced robust humoral and cellular immune responses, including the abundant production of neutralizing antibodies, CD4⁺ T lymphocytes, and the Th1 (IFN-γ) and Th2 (IL-4 and IL-6)

cytokines.  We also confirmed that LN16-A provided 100% protection against subtype B aMPV and significantly reduced viral shedding and turbinate inflammation.  Our findings suggest that the LN16-A strain is a promising live attenuated vaccine candidate that can prevent infection with subtype B aMPV.

Improving plant resistance to Verticillium wilt (VW), which causes massive losses in Gossypium hirsutum, is a global challenge.  Crop plants need to efficiently allocate their limited energy resources to maintain a balance between growth and defense.  However, few transcriptional regulators specifically respond to Verticillium dahliae and the underlying mechanism has not been identified in cotton.  In this study, we found that the that expression of most R2R3-MYB members in cotton is significantly changed by V. dahliae infection relative to the other MYB types.  One novel R2R3-MYB transcription factor (TF) that specifically responds to V. dahliae, GhMYB3D5, was identified.  GhMYB3D5 was not expressed in 15 cotton tissues under normal conditions, but it was dramatically induced by V. dahliae stress.  We functionally characterized its positive role and underlying mechanism in VW resistance.  Upon V. dahliae infection, the up-regulated GhMYB3D5 bound to the GhADH1 promoter and activated GhADH1 expression.  In addition, GhMYB3D5 physically interacted with GhADH1 and further enhanced the transcriptional activation of GhADH1.  Consequently, the transcriptional regulatory module GhMYB3D5-GhADH1 then promoted lignin accumulation by improving the transcriptional levels of genes related to lignin biosynthesis (GhPAL, GhC4H, Gh4CL, and GhPOD/GhLAC) in cotton, thereby enhancing cotton VW resistance.  Our results demonstrated that the GhMYB3D5 promotes defense-induced lignin accumulation, which can be regarded as an effective way to orchestrate plant immunity and growth. 

The Janus kinase (JAK)–signal transducer and activator of transcription (STAT) signaling pathway plays a crucial role in innate immunity by inducing antiviral proteins in response to interferon signals. Marek’s disease virus (MDV), a member of the alpha-herpes virus family, exerts potent tumorigenic and immunosuppressive effects. Recent studies have primarily focused on the tumorigenic mechanisms of MDV, and the mechanism of immune evasion has not been fully understood. In this study, we showed that MDV reduced the production of interferon-stimulated gene (ISGs) by inhibiting the phosphorylation and nuclear translocation of STAT1. Using a dual-luciferase reporter system, we screened for viral proteins that significantly suppress interferon-stimulated response element (ISRE) promoter activity. Meq overexpression markedly reduced ISRE promoter activity and ISG expression, whereas infection with Meq-deficient MDV induced higher ISG production in vitro and in vivo than infection with wild-type MDV. Meq also inhibited the phosphorylation and nuclear translocation of STAT1. Further experiments showed that Meq interacted with JAK1 and tyrosine kinase 2 (TYK2) and thereby inhibited JAK1–STAT1 interactions. Meq degraded TYK2 via a caspase-mediated pathway. The Meq-deficient MDV mutant replicated less efficiently than the wild-type MDV, both in vitro and in vivo. Collectively, these findings demonstrate that Meq played an immunosuppressive role in MDV by attenuating the JAK–STAT signaling pathway, which facilitated escape from innate immune-surveillance mechanisms.

The Huang-Huai-Hai wheat region (HHHR) is characterized by the largest cultivation area and yield among all the major wheat-producing regions in China.  Over the past 70 years, significant advances in wheat breeding have been achieved in this region, resulting in high and stable yields as well as improved disease resistance.  However, there is a notable deficiency in the systematic molecular-level analyses of wheat breeding advantages in HHHR.  To bridge this gap, we used a Wheat 55K SNP array to evaluate 384 accessions from a core collection of wheat germplasms across China to systematically analyze the distribution patterns of beneficial haplotypes associated with traits related to yield and powdery mildew resistance specific to HHHR.  Our findings indicate that varieties from HHHR demonstrate significantly superior performance in terms of yield-related traits and powdery mildew resistance compared to those from other wheat regions.  Using genome-wide association studies (GWAS) analysis, we identified the QTNs associated with both grain yield and powdery mildew resistance.  Importantly, beneficial haplotypes were found at significantly higher frequencies in the HHHR than in other wheat-growing regions.  Based on these haplotypes, the MFP-a gene was identified as potentially regulating jasmonic acid synthesis while also playing a role in grain development and conferring powdery mildew resistance.  Furthermore, identity by descent (IBD) analysis revealed specific conserved genomic segments that have become fixed through selective breeding practices in HHHR, which may serve as invaluable resources for the targeted enhancement of yield and disease resistance traits in other wheat-growing areas.  Finally, using the Aimengniu breeding lineage as a case study, we elucidated the genetic basis underlying the key founder parental formations utilized in breeding programs.  This study not only provides essential references and guidance for future molecular breeding initiatives in China but also has implications for enhancing wheat production worldwide.

In floodplain wetlands, alterations in hydrological patterns resulting from climate change and human activities could potentially diminish the carbon sequestration capacity of the soils, thereby having a negative impact on global climate change. However, the magnitude of the influence of hydrological regime change on soil carbon remains inadequately monitored. To address this research gap, we collected 306 upper layer (0-20 cm) soil samples from the Dongting Lake floodplain between 2013 and 2022. The Random Forest (RF) algorithm was used to analyze the spatial distribution of soil organic carbon (SOC) in the upper soil layer of Dongting Lake floodplain and the impact of climate and hydrological changes in the past decade on surface SOC in the East Dongting Lake area was studied. In 2022, the SOC concentration of the Dongting Lake floodplain upper layer soil ranged from 3.34 to 17.67 g kg^-1, averaging 10.43 g kg^-1, with a corresponding SOC density of 2.65±0.49 kg m^-2 and total SOC stock of 6.82 Tg C (2.87–13.48 Tg C). From 2013 to 2022, the SOC concentration of the upper soil layer of the East Dongting Lake area decreased from 18.37 g kg^-1 to 10.82 g kg^-1. This reduction could be attributed to climate and hydrological changes which reduce SOC input by reducing vegetation growth and accelerating SOC decomposition. Above 21.4 m elevation, the amount of SOC loss increased with elevation, the loss being related to the decline in Miscanthus community biomass and greater susceptibility of higher altitude areas to climate and hydrological changes. Our results highlight the need for strengthening wetland SOC management to increase SOC in the soils to help combat climate change.