Songchong Lu

Vicia villosa Roth var. glabrescens (smooth vetch) is an economically important legume cover crop valued for its nitrogen-fixing capacity, high biomass yield, and adaptability across diverse agroecosystems. Here, we present a chromosome-scale, high-quality genome assembly of V. villosa var. glabrescens, constructed using PacBio HiFi sequencing combined with Hi-C scaffolding. The assembly spans 3.70 Gb with a scaffold N50 of 4.69 Mb and exhibits lower heterozygosity (0.9%) compared to V. villosa Roth (3.1%). Genome analysis revealed significant expansion of long terminal repeat retrotransposons (LTR-RTs), as well as lineage-specific proliferation of miniature inverted-repeat transposable elements (MITEs) in V. villosa var. glabrescens. Comparative genomics with V. villosa Roth highlighted gene family expansions associated with trichome development, providing insights into the genetic basis of morphological and adaptive differences within the Vicia species. This reference genome provides a foundational resource for accelerating the breeding of V. villosa varieties with enhanced agronomic traits and contributes to a broader understanding of legume genomics and plant genome evolution.

Soil salinization poses a serious threat to plant development and represents a major obstacle to the sustainable production of crops worldwide. Melatonin (MT) contributes prominently to plant tolerance against abiotic environments. However, the molecular basis of transcriptional regulation underlying melatonin accumulation in tomato under saline–alkali stress is still largely unknown. Herein, we identify SlNAC2, a NAC transcription factor in tomato induced by saline–alkali stress, which suppresses the key melatonin biosynthetic genes SlCOMT2 and SlSNAT, while activating SlCV, a gene linked to reactive oxygen species (ROS) accumulation and programmed cell death. These regulatory effects reduce MT levels and promote excessive ROS production, ultimately altering the plant’s tolerance to saline–alkali stress. Silencing of SlNAC2 through the RNA interference method significantly improves saline–alkali tolerance in tomato, while its constitutive overexpression shows increased susceptibility to saline–alkali stress. Further evidence reveals that under saline–alkali conditions, SlNAC2 directly targets cis-elements of SlCOMT2 and SlSNAT promoters, suppressing their transcription and consequently reducing melatonin levels, whereas simultaneously binding to the SlCV promoter to activate its expression, ultimately leading to ROS accumulation. Moreover, comprehensive protein interaction analyses confirmed that SlNAC2 physically associates with SlDREB2, a DREB-type transcription factor involved in salt stress response. Through its interaction with SlNAC2, SlDREB2 partially attenuates its repression of SlCOMT2 and SlSNAT, thereby increasing melatonin accumulation and ROS scavenging, ultimately enhancing tomato’s resilience to saline–alkali stress conditions. Collectively, our findings reveal a SlNAC2–SlDREB2 regulatory module that finely tunes melatonin synthesis and ROS levels to regulate tomato’s response to saline–alkali stress, providing new strategies for developing stress-resilient tomato varieties.

Leaf senescence is the terminal stage of leaf development, and its initiation and progression are closely controlled by the integration of a myriad of endogenous signals and environmental stimuli. It has been documented that WRKY transcription factors (TFs) play essential roles in regulating leaf senescence, yet the molecular mechanism of WRKY-mediated leaf senescence still lacks detailed elucidation in crop plants. In this study, we cloned and identified a tobacco WRKY TF gene, designated NtWRKY70b, acting as a positive regulator of natural leaf senescence. The expression profile analysis showed that NtWRKY70b transcript levels were induced by aging and hydrogen peroxide (H₂O₂) and downregulated upon hydrogen sulfide (H₂S) treatment. The physiological and biochemical assays revealed that overexpression of NtWRKY70b (OE) clearly promoted leaf senescence, triggering increased levels of reactive oxygen species (ROS) and decreased H₂S content, while disruption of NtWRKY70b by chimeric repressor silencing technology (SRDX) significantly delayed the onset of leaf senescence, leading to a decreased accumulation of ROS and elevated concentration of H₂S. The quantitative real-time PCR analysis showed that the expression levels of various senescence-associated genes and ROS biosynthesis-related genes (NtRbohD and NtRbohE) were upregulated in OE lines, while the expression of H₂S biosynthesis-related genes (NtDCD and NtCYSC1) were inhibited in OE lines. Furthermore, the Yeast one-hybrid analysis (Y1H) and dual luciferase assays showed that NtWRKY70b could directly upregulate the expression of an ROS biosynthesis-related gene (NtRbohD) and a chlorophyll degradation-related gene (NtPPH) by binding to their promoter sequences. Accordingly, these results indicated that NtWYKY70b directly activated the transcript levels of NtRbohD and NtPPH and repressed the expression of NtDCD and NtCYCS1, thereby promoting ROS accumulation and impairing the endogenous H₂S production, and subsequently accelerating leaf aging. These observations improve our knowledge of the regulatory mechanisms of WRKY TFs controlling leaf senescence and provide a novel method for ensuring high agricultural crop productivity via genetic manipulation of leaf senescence in crops.

Leaf senescence is a comprehensive process performed by integrating various internal and external signals, followed by nutrient reallocation, especially via organic nitrogen (e.g., amino acids) mobilization. Amino acid (AA) transporters play an important role in crop growth and development by participating in the process of organic nitrogen remobilization. However, the biological functions and downstream effectors of amino acid transporters involved in leaf senescence are still poorly understood. In the present study, we cloned and characterized a cationic amino acid transporter gene, NtCAT1, from tobacco (K326). We found that NtCAT1 transcript levels were induced by age and abscisic acid (ABA). The NtCAT1 protein was highly localized in the plasma membrane. The overexpressing NtCAT1 line (OECAT1) showed early leaf senescence, accompanied with increased reactive oxygen species (ROS) and ABA content. By contrast, the NtCAT1 mutant (ntcat1-36) generated by the CRSPR/Cas9 system, showed a delayed-senescence phenotype with a decreased accumulation of ROS and ABA. Moreover, we discovered that the overexpression of NtCAT1 could downregulate the expression of the target of rapamycin (TOR) kinase gene and upregulate the transcript levels of ABA-related genes during leaf senescence compared with wild type (WT), while the expression of these genes in ntcat1-36 plants exhibited inverse trends. Furthermore, an analysis of the amino acid concentration demonstrated that NtCAT1 transgenic plants displayed dramatic changes in the amino acid profile during leaf senescence. In summary, our results suggest that NtCAT1 could promote leaf senescence via the increased biosynthesis of ABA, and our study provides new insights into the molecular mechanism of leaf senescence.

The sea cucumber (Apostichopus japonicus) is the main economic species in China and has a significant role in aquaculture. Gut microbiome composition is closely related to external environments. In this study, we identified the effects of seasonal changes on the composition and main metabolites of symbiotic microorganisms in the intestine of A. japonicus. We used 16S rRNA sequencing to identify the composition of symbiotic microorganisms in different seasons. Intestinal metabolites were determined using liquid chromatography with tandem mass spectrometry, which linked symbiotic microorganisms to intestinal metabolites. Analyzing changes in intestinal microbial composition across different seasons. The results showed that seasonal changes of intestinal microorganisms were significant, A. japonicus were infected by Vibrio easily in summer, Stigmasterol and sitosterol could affect the growth of body wall of A. japonicus. It is vital importance for A. japonicus that the results benefit for the growth, immunity and aquaculture.

Soil salinity severely threatens plant growth and crop performance. Hydrogen sulfide (H₂S), a plant signal molecule, has been implicated in the regulation of plant responses to salinity stress. However, it is unclear how the transcriptional network regulates H₂S biosynthesis during salt stress response. In this study, we identify a rice NAC (NAM, ATAF and CUC) transcription factor, OsNAC35-like (OsNACL35), from a salt-tolerant cultivar ‘Sea Rice 86′ (SR86) and further show that it may have improved salt tolerance via enhanced H₂S production. The expression of OsNACL35 was significantly upregulated by high salinity and hydrogen peroxide (H₂O₂). The OsNACL35 protein was localized predominantly in the nucleus and was found to have transactivation activity in yeast. The overexpression of OsNACL35 (OsNACL35-OE) in japonica cultivar Nipponbare ramatically increased resistance to salinity stress, whereas its dominant-negative constructs (SUPERMAN repression domain, SRDX) conferred hypersensitivity to salt stress in the transgenic lines at the vegetative stage. Moreover, the quantitative real-time PCR analysis showed that many stress-associated genes were differentially expressed in the OsNACL35-OE and OsNACL35-SRDX lines. Interestingly, the ectopic expression of OsNACL35 triggered a sharp increase in H₂S content by upregulating the expression of a H₂S biosynthetic gene, OsDCD1, upon salinity stress. Furthermore, the dual luciferase and yeast one-hybrid assays indicated that OsNACL35 directly upregulated the expression of OsDCD1 by binding to the promoter sequence of OsDCD1. Taken together, our observations illustrate that OsNACL35 acts as a positive regulator that links H₂S production to salt stress tolerance, which may hold promising utility in breeding salt-tolerant rice cultivar.

Hydrogen sulfide (H₂S) has been shown to participate in various stress responses in plants, including drought, salinity, extreme temperatures, osmotic stress, and heavy metal stress. Manganese (Mn), as a necessary nutrient for plant growth, plays an important role in photosynthesis, growth, development, and enzymatic activation of plants. However, excessive Mn²⁺ in the soil can critically affect plant growth, particularly in acidic soil. In this study, the model plant Arabidopsis thaliana was used to explore the mechanism of H₂S participation and alleviation of Mn stress. First, using wild-type Arabidopsis with excessive Mn²⁺ treatment, the following factors were increased: H₂S content, the main H₂S synthetase L-cysteine desulfhydrase enzyme (AtLCD) activity, and the expression level of the AtLCD gene. Further, using the wild-type, AtLCD deletion mutant (lcd) and overexpression lines (OE5 and OE32) as materials, the phenotype of Arabidopsis seedlings was observed by exogenous application of hydrogen sulfide donor sodium hydrosulfide (NaHS) and scavenger hypotaurine (HT) under excessive Mn²⁺ treatment. The results showed that NaHS can significantly alleviate the stress caused by Mn²⁺, whereas HT aggravates this stress. The lcd mutant is more sensitive to Mn stress than the wild type, and the overexpression lines are more resistant. Moreover, the mechanism of H₂S alleviating Mn stress was determined. The Mn²⁺ content and the expression of the Mn transporter gene in the mutant were significantly higher than those of the wild-type and overexpression lines. The accumulation of reactive oxygen species was significantly reduced in NaHS-treated Arabidopsis seedlings and AtLCD overexpression lines, and the activities of various antioxidant enzymes (SOD, POD, CAT, APX) also significantly increased. In summary, H₂S is involved in the response of Arabidopsis to Mn stress and may alleviate the inhibition of Mn stress on Arabidopsis seedling growth by reducing Mn²⁺ content, reducing reactive oxygen species content, and enhancing antioxidant enzyme activity. This study provides an important basis for further study of plant resistance to heavy metal stress.