Excessive climate warming exacerbates nitrogen limitation on microbial metabolism in an alpine meadow of the Tibetan Plateau: Evidence from soil ecoenzymatic stoichiometry.

Soil ecoenzymatic stoichiometry reflects the dynamic equilibrium between microorganism's nutrient requirements and resource availability. However, uncertainties persist regarding the key determinants of nutrient restriction in relation to microbial metabolism under varying degrees of warming. Our long-term and multi-level warming field experiment (control treatment, +0.42 °C, +1.50 °C, +2.55 °C) in a typical alpine meadow unveiled a decline in carbon (C)- and nitrogen (N)-acquired enzymes with escalating warming magnitudes, while phosphorus (P)-acquired enzymes displayed an opposite trend. Employing enzymatic stoichiometry modeling, we assessed the nutrient limitations of microbial metabolic activity and found that C and N co-limited microbial metabolic activities in the alpine meadow. Remarkably, high-level warming (+2.55 °C) exacerbated microbe N limitation, but alleviate C limitations. The structural equation modeling further indicated that alterations in soil extracellular enzyme characteristics (SES) were more effectively elucidated by microbial characteristics (microbial biomass C, N, P, and their ratios) rather than by soil nutrients (total nutrient contents and their ratios). However, the microbial control over SES diminished with higher levels of warming magnitude. Overall, our results provided novel evidence that the factors driving microbe metabolic limitation may vary with the degree of warming in Tibet alpine grasslands. Changes in nutrient demand for microorganism's metabolism in response to warming should be considered to improve nutrient management in adapting to different future warming scenarios.

Integrated physicochemical, hormonal, and transcriptomic analysis reveals the underlying mechanism of callus formation in Pinellia ternata hydroponic cuttings.

Introduction: P. ternata is a perennial herb of the family Araceae that grows in China and has various medicinal properties and applications. At present, the artificial cultivation of P. ternata is constrained by seedling propagation. To address the problems of low seedling breeding propagation efficiency and high cost, our group has developed a highly efficient cultivation technology for "hydroponic cuttings of P. ternata "for the first time. P. ternata is used as the source material and is grown in a hydroponic system, increasing the seedling production rate 10-fold compared with the traditional cultivation mode. However, the callus formation mechanism in cuttings from hydroponic cultivation is still remains unclear. Methods: In order to better understand the biological process of callus formation in cuttings from hydroponic P. ternata, anatomical characterization, endogenous hormone content determination and transcriptome sequencing were performed on five callus stages from early growth to early senescence. Results: Regarding the four major hormones during the callus developmental stages of P. ternata hydroponic cuttings, cytokinins showed an increasing trend during callus formation. IAA(indole-3-acetic acid) and abscisic acid contents increased at 8d and then decreased, while jasmonic acid content gradually decreased. A total of 254137 unigenes were identified by transcriptome sequencing in five callus formation stages. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of the differentially expressed genes (DEGs) that differentially expressed unigenes were involved in various plant hormone signaling and hormone synthesis-related pathways. The expression patterns of 7 genes were validated using quantitative real-time PCR. Discussion: This study presented integrated transcriptomic and metabolic analysis approach to obtain insights into the underlying biosynthetic mechanisms and function of key hormones involved in the callus formation process from hydroponic P. ternata cuttings.

Climate warming alters the relative importance of plant root and microbial community in regulating the accumulation of soil microbial necromass carbon in a Tibetan alpine meadow.

Climate warming is predicted to considerably affect variations in soil organic carbon (SOC), especially in alpine ecosystems. Microbial necromass carbon (MNC) is an important contributor to stable soil organic carbon pools. However, accumulation and persistence of soil MNC across a gradient of warming are still poorly understood. An 8-year field experiment with four levels of warming was conducted in a Tibetan meadow. We found that low-level (+0-1.5°C) warming mostly enhanced bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and total MNC compared with control treatment across soil layers, while no significant effect was caused between high-level (+1.5-2.5°C) treatments and control treatments. The contributions of both MNC and BNC to soil organic carbon were not significantly affected by warming treatments across depths. Structural equation modeling analysis demonstrated that the effect of plant root traits on MNC persistence strengthened with warming intensity, while the influence of microbial community characteristics waned along strengthened warming. Overall, our study provides novel evidence that the major determinants of MNC production and stabilization may vary with warming magnitude in alpine meadows. This finding is critical for updating our knowledge on soil carbon storage in response to climate warming.

T cell immunity induced by a bivalent Salmonella-based CEACAM6 and 4-1BBL vaccines in a rat colorectal cancer model.

The present study investigated the anti-tumor mechanisms of recombinant non-specific cross-reacting antigen (CEACAM6) and 4-1BB ligand (4-1BBL) Salmonella-based vaccines, and the effect that these vaccinations have on memory T cells and T helper (Th) cell polarization. Colon tumors were induced in rats via 1,2-dimethylhydrazine (DMH) injections. Rats were then treated with injections of attenuated Salmonella typhimurium carrying pIRES-CEACAM6, pIRES-4-1BBL or pIRES-CEACAM6-4-1BBL. In total, 4 vaccine injections, one every other week, were administered during the 8 weeks subsequent to the DMH injection. Rats were sacrificed 18 weeks subsequent to the DMH injections, and the colons and spleens were collected for further analysis. Cluster of differentiation (CD) 45RO, interleukin (IL)-4 and IL-17 expression was analyzed in colon tumor tissues, and the expression of interferon (IFN)-γ, CD3+, CD4+, CD8+, CD56+, forkhead/winged-helix transcription factor box P3 (FOXP3+), IL-4 and IL-17 were analyzed in splenic tissues. Compared with the pIRES/SL3261 group, the pIRES-CEACAM6-4-1BBL/SL3261 treatment group had a significantly higher number of CD45RO+ expressing tumor infiltrating lymphocytes and lower expression levels of IL-4 and IL-17. Splenic tissues from the same treatment group exhibited significantly increased expression of IFN-γ, CD3+ and CD8+ and reduced expression levels of Foxp3, IL-4 and IL-7. CD56+ T cell expression was increased in all groups except for the group that received no vaccine. The present study concluded that the combined CEACAM6 and 4-1BBL-attenuated recombinant Salmonella vaccine was able to inhibit the growth of DMH-induced colorectal tumors. This was mediated by generating an anti-tumor immune response, increasing the number of of CD45RO+ memory T cells, decreasing the number of FOXP3+ cells and promoting Th1 polarization.