分类： 生物学 >> 生态学 提交时间： 2022-11-08 合作期刊: 《干旱区科学》
摘要：Competition, spatial pattern, and regeneration are important factors affecting community composition, structure, and dynamics. In this study, we surveyed 300 quadrats from three dunes (i.e., fixed dunes, semifixed dunes, and mobile dunes) in the Gurbantunggut Desert, Northwest China, from late May to early June in 2021. The intraspecific and interspecific competition, spatial pattern, and regeneration of Haloxylon ammodendron and Haloxylon persicum were studied using the Hegyi competition index and point pattern analysis methods. The results showed that the optimal competition distance of the objective tree in the H. ammodendron and H. persicum communities was 6 m. The intraspecific and interspecific competition of H. ammodendron was the greatest in fixed dunes, while the competition intensity of H. persicum in semifixed dunes and mobile dunes was greater than that in fixed dunes. The order of competition intensity of the two populations was seedlings>saplings>adults, and the competition intensity gradually decreased with the increase in plant diameter. The spatial distribution pattern of the three life stages of H. ammodendron and H. persicum was random, and there were no correlations between seedlings and saplings, adults and saplings, and seedlings and adults. The density of regenerated seedlings and saplings of H. ammodendron in the three dunes followed the order of fixed dunes>semifixed dunes>mobile dunes, and that of H. persicum in the three dunes followed the order of mobile dunes>semifixed dunes>fixed dunes. Therefore, when artificially planting H. ammodendron and H. persicum for sand control, the planting interval should be 6 m, and seedlings should be planted next to adults to minimize the competition between plants, which can promote the renewal of H. ammodendron and H. persicum and the stabilization of the ecosystem.
分类： 生物学 >> 植物学 提交时间： 2024-04-15 合作期刊: 《干旱区科学》
摘要： The maintenance of sand-fixing vegetation is important for the stability of artificial sand-fixing systems in which seed dispersal plays a key role. Based on field wind tunnel experiments using 11 common plant species on the southeastern edge of the Tengger Desert, China, we studied the secondary seed dispersal in the fixed and semi-fixed sand dunes as well as in the mobile dunes in order to understand the limitations of vegetation regeneration and the maintenance of its stability. Our results indicated that there were significant variations among the selected 11 plant species in the threshold of wind speed (TWS). The TWS of Caragana korshinskii was the highest among the 11 plant species, whereas that of Echinops gmelinii was the lowest. Seed morphological traits and underlying surface could generally explain the TWS. During the secondary seed dispersal processes, the proportions of seeds that did not disperse (no dispersal) and only dispersed over short distance (short-distance dispersal within the wind tunnel test section) were significantly higher than those of seeds that were buried (including lost seeds) and dispersed over long distance (long-distance dispersal beyond the wind tunnel test section). Compared with other habitats, the mobile dunes were the most difficult places for secondary seed dispersal. Buried seeds were the easiest to be found in the semi-fixed sand dunes, whereas fixed sand dunes were the best sites for seeds that dispersed over long distance. The results of linear mixed models showed that after controlling the dispersal distance, smaller and rounder seeds dispersed farther. Shape index and wind speed were the two significant influencing factors on the burial of seeds. The explanatory power of wind speed, underlying surface, and seed morphological traits on the seeds that did not disperse and dispersed over short distance was far greater than that on the seeds that were buried and dispersed over long distance, implying that the processes and mechanisms of burial and long-distance dispersal are more complex. In summary, most seeds in the study area either did not move, were buried, or dispersed over short distance, promoting local vegetation regeneration.
分类： 生物学 >> 生态学 提交时间： 2023-12-20 合作期刊: 《干旱区科学》
摘要： Grassland degradation can alter the structure and function of ecosystem and soil seed bank. Therefore, estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial. We selected grasslands with three levels of degradation, namely non-degraded (ND), mildly degraded (MD), and heavily degraded (HD) to analyze the effect of grassland degradation on soil seed bank, as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands, China. Soil samples from each level were collected in May, before seedling emergence, in August, after completion of transient seed bank germination, and in December, after seed dispersal, to determine the seed density and species composition through germination experiment. Result showed that a total of 35 plant species was identified, including 15 species observed in both soil seed bank and above-ground vegetation. A total of 19, 15, and 14 species of soil seed bank were identified in December, May, and August, respectively. The most abundant species in soil seed bank were Compositae (5 species), followed by Poaceae (4 species), and Cyperaceae (3 species). Degradation level has no significant impact on species richness and Shannon- Wiener index of soil seed bank. In addition, sampling month and grassland degradation affected soil seed bank density, in which December>May>August, and ND>MD>HD, indicating that density of transient seed bank was greater than persistent seed bank. Soil seed bank density of surface layer (05 cm) accounting for 42%72% of the total density, which was significantly higher than that of deep layer (510 cm). Similarity of species composition between vegetation and soil seed bank was low, and it increased with degradation level (ranged from 0.14 to 0.69). We concluded that grassland degradation affects soil seed bank density more than species diversity, and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland. Therefore, it is unlikely that degraded alpine meadow can be restored solely through soil seed bank.
分类： 生物学 >> 生物物理学 >> 免疫学 提交时间： 2016-05-15
Xia, Pengyan
Wang, Shuo
Du, Ying
Huang, Guanling
Fan, Zusen
Huang, Guanling
Satoh, Takashi
Akira, Shizuo
摘要： The lineage commitment of HSCs generates balanced myeloid and lymphoid populations in hematopoiesis. However, the underlying mechanisms that control this process remain largely unknown. Here, we show that insulin-insulin receptor (InsR) signaling is required for lineage commitment of multipotent progenitors (MPPs). Deletion of Insr in murine bone marrow causes skewed differentiation of MPPs to myeloid cells. mTOR acts as a downstream effector that modulates MPP differentiation. mTOR activates Stat3 by phosphorylation at serine 727 under insulin stimulation, which binds to the promoter of Ikaros, leading to its transcription priming. Our findings reveal that the insulin-InsR signaling drives MPP differentiation into lymphoid lineages in early lymphopoiesis, which is essential for maintaining a balanced immune system for an individual organism.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-11
摘要： Mesenchymal stem cells (MSCs) are a reliable cell source for tissue regeneration. However, the molecular mechanisms underlying the directed differentiation of MSCs remain unclear; thus, their use is limited. Here, we investigate HOXB7 function in the osteogenic differentiation potentials of MSCs using stem cells from apical papilla (SCAPs) and bone marrow stem cells (BMSCs). The HOXB7 gene is highly expressed in BMSCs compared with dental tissue-derived MSCs. We found that, in vitro, over-expression of HOXB7 in SCAPs enhanced alkaline phosphatase (ALP) activity and mineralization. HOXB7 over-expression affected the mRNA expression of osteonectin (ON), collagen alpha-2(I) chain (COL1A2), bone sialoprotein (BSP), and osteocalcin (OCN), led to the expression of the key transcription factor, runt-related transcription factor 2 (RUNX2), and promoted SCAP osteogenic differentiation in vitro. The knock-down of HOXB7 inhibited ALP activity, mineralization, and the expression of ON, BSP, COL1A2, OCN, and RUNX2 in BMSCs in vitro. In addition, transplant experiments in nude mice confirmed that SCAP osteogenesis was triggered when HOXB7 was activated. Furthermore, Over-expression of HOXB7 significantly increased the levels of HOXB7 associated with the BSP promoter by ChIP assays. Taken together, these results indicate that HOXB7 enhances SCAP osteogenic differentiation by up-regulating RUNX2 and directly activating transcript of BSP. Thus, the activation of HOXB7 signaling might improve tissue regeneration mediated by MSCs. These results provide insight into the mechanism underlying the directed differentiation of MSCs.
分类： 生物学 >> 生物物理学 提交时间： 2016-05-05
Chen, Jiamei
Liu, Chenghai
Liu, Ping
Chen, Jiamei
Gao, Wei
Zhou, Ping
Ma, Xiaocui
Tschudy-Seney, Benjamin
Zern, Mark A.
Duan, Yuyou
Chen, Jiamei
Gao, Wei
Zhou, Ping
Ma, Xiaocui
Tschudy-Seney, Benjamin
Zern, Mark A.
Duan, Yuyou
Chen, Jiamei
Duan, Yuyou
Gao, Wei
摘要： Chinese medicine, Fuzhenghuayu (FZHY), appears to prevent fibrosis progression and improve liver function in humans. Here we found that FZHY enhanced hepatocyte differentiation from human embryonic stem cells (hESC). After treatment with FZHY, albumin expression was consistently increased during differentiation and maturation process, and expression of metabolizing enzymes and transporter were also increased. Importantly, expression of mesenchymal cell and cholangiocyte marker was significantly reduced by treatment with FZHY, indicating that one possible mechanism of FZHY's role is to inhibit the formation of mesenchymal cells and cholangiocytes. Edu-labelled flow cytometric analysis showed that the percentage of the Edu positive cells was increased in the treated cells. These results indicate that the enhanced proliferation involved hepatocytes rather than another cell type. Our investigations further revealed that these enhancements by FZHY are mediated through activation of canonical Wnt and ERK pathways and inhibition of Notch pathway. Thus, FZHY not only promoted hepatocyte differentiation and maturation, but also enhanced hepatocyte proliferation. These results demonstrate that FZHY appears to represent an excellent therapeutic agent for the treatment of liver fibrosis, and that FZHY treatment can enhance our efforts to generate mature hepatocytes with proliferative capacity for cell-based therapeutics and for pharmacological and toxicological studies.
分类： 生物学 >> 植物学 >> 植物生态学和植物地理学 提交时间： 2016-05-04
摘要： Biochar management has been proposed as a possible tool to mitigate anthropogenic CO2 emissions, and thus far its impacts in forested environments remain poorly understood. We conducted a large-scale, replicated field experiment using 0.05-ha plots in the boreal region in northern Sweden to evaluate how soil and vegetation properties and processes responded to biochar application and the disturbance associated with burying biochar in the soil. We employed a randomized block design, where biochar and soil mixing treatments were established in factorial combination (i.e., control, soil mixing only, biochar only, and biochar and soil mixing; n = 6 plots of each). After two growing seasons, we found that biochar application enhanced net soil N mineralization rates and soil NH4+ concentrations regardless of the soil mixing treatment, but had no impact on the availability of NO3− , the majority of soil microbial community parameters, or soil respiration. Meanwhile, soil mixing enhanced soil NO3− concentrations, but had negative impacts on net N mineralization rates and several soil microbial community variables. Many of the effects of soil mixing on soil nutrient and microbial community properties were less extreme when biochar was also added. Biochar addition had almost no effects on vegetation properties (except for a small reduction in species richness of the ground layer vegetation), while soil mixing caused significant reductions in graminoid and total ground layer vegetation cover, and enhanced seedling survival rates of P. sylvestris, and seed germination rates for four tree species. Our results suggest that biochar application can serve as an effective tool to store soil C in boreal forests while enhancing NH4+ availability. They also suggest that biochar may serve as a useful complement to site preparation techniques that are frequently used in the boreal region, by enhancing soil fertility and reducing nutrient losses when soils are scarified during site preparation.
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