Marine mammals are important models for studying convergent evolution and aquatic adaption, and thus reference genomes of marine mammals can provide evolutionary insights. Here, we present the first chromosome‐level marine mammal genome assembly based on the data generated by the BGISEQ‐500 platform, for a stranded female sperm whale (Physeter macrocephalus). Using this reference genome, we performed chromosome evolution analysis of the sperm whale, including constructing ancestral chromosomes, identifying chromosome rearrangement events and comparing with cattle chromosomes, which provides a resource for exploring marine mammal adaptation and speciation. We detected a high proportion of long interspersed nuclear elements and expanded gene families, and contraction of major histocompatibility complex region genes which were specific to sperm whale. Using comparisons with sheep and cattle, we analysed positively selected genes to identify gene pathways that may be related to adaptation to the marine environment. Further, we identified possible convergent evolution in aquatic mammals by testing for positively selected genes across three orders of marine mammals. In addition, we used publicly available resequencing data to confirm a rapid decline in global population size in the Pliocene to Pleistocene transition. This study sheds light on the chromosome evolution and genetic mechanisms underpinning sperm whale adaptations, providing valuable resources for future comparative genomics. 相似文献
Litterfall dynamics (production, seasonality and nutrient composition) are key factors influencing nutrient cycling. Leaf litter characteristics are modified by species composition, site conditions and water availability. However, significant evidence on how large‐scale, global circulation patterns affect ecophysiological processes at tree and ecosystem level remains scarce due to the difficulty in separating the combined influence of different factors on local climate and tree phenology. To fill this gap, we studied links between leaf litter dynamics with climate and other forest processes, such as tree‐ring width (TRW) and intrinsic water‐use efficiency (iWUE) in two mixtures of Scots pine (Pinus sylvestris L.) and European beech (Fagus sylvatica L.) in the south‐western Pyrenees. Temporal series (18 years) of litterfall production and elemental chemical composition were decomposed following the ensemble empirical mode decomposition method and relationships with local climate, large‐scale climatic indices, TRW and Scots pine's iWUE were assessed. Temporal trends in N:P ratios indicated increasing P limitation of soil microbes, thus affecting nutrient availability, as the ecological succession from a pine‐dominated to a beech‐dominated forest took place. A significant influence of large‐scale patterns on tree‐level ecophysiology was explained through the impact of the North Atlantic Oscillation (NAO) and El Niño–Southern Oscillation (ENSO) on water availability. Positive NAO and negative ENSO were related to dry conditions and, consequently, to early needle shedding and increased N:P ratio of both species. Autumn storm activity appears to be related to premature leaf abscission of European beech. Significant cascading effects from large‐scale patterns on local weather influenced pine TRW and iWUE. These variables also responded to leaf stoichiometry fallen 3 years prior to tree‐ring formation. Our results provide evidence of the cascading effect that variability in global climate circulation patterns can have on ecophysiological processes and stand dynamics in mixed forests. 相似文献
Increasing drought and extreme rainfall are major threats to maize production in the United States. However, compared to drought impact, the impact of excessive rainfall on crop yield remains unresolved. Here, we present observational evidence from crop yield and insurance data that excessive rainfall can reduce maize yield up to ?34% (?17 ± 3% on average) in the United States relative to the expected yield from the long‐term trend, comparable to the up to ?37% loss by extreme drought (?32 ± 2% on average) from 1981 to 2016. Drought consistently decreases maize yield due to water deficiency and concurrent heat, with greater yield loss for rainfed maize in wetter areas. Excessive rainfall can have either negative or positive impact on crop yield, and its sign varies regionally. Excessive rainfall decreases maize yield significantly in cooler areas in conjunction with poorly drained soils, and such yield loss gets exacerbated under the condition of high preseason soil water storage. Current process‐based crop models cannot capture the yield loss from excessive rainfall and overestimate yield under wet conditions. Our results highlight the need for improved understanding and modeling of the excessive rainfall impact on crop yield. 相似文献
Ecological restoration studies have been widely conducted for many years to solve eco‐environmental problems. However, no publications offer a systematic and quantitative analysis of the evolution of the field of ecological restoration. To address this knowledge gap, for the first time, we applied a bibliometric analysis approach to analyze ecological restoration studies. We analyzed 3,929 articles published between 1988 and 2017 catalogued in the Science Citation Index Expanded database and the Social Sciences Citation Index database. The results show that annual article output stably increased after 2004, and the number of annual articles of each country has also increased notably since then. The United States occupies the leading position in ecological restoration studies, with China attaining a close second position in recent years. Four institutions and seven journals are outstanding in the field of ecological restoration. Academic collaborations of authors or institutions exhibit an increasing trend, but international collaboration needs to be strengthened because eco‐environmental problems are a global challenge. Forest, grassland, and wetland ecosystems have received the most attention. Biodiversity, ecosystem services, and climate change are core issues of ecological restoration studies and are predicted to remain the research hotspots in the future. Novel ecosystems are likely to become one of the most important research areas in the near future. More importantly, it is crucial for researchers to places more emphasis on social issues of ecological restoration in the future. 相似文献
Objectives: Mounting evidence has demonstrated that C-Phycocyanin (C-PC) exhibits marked antitumor activity in a wide type of tumors, such as pancreas cancer, breast carcinoma, lung cancer, and colon cancer. The current study aimed to confirm the antitumor efficacy of C-PC in esophageal squamous cell carcinoma (ESCC).
Methods: The efficacy of C-PC was evaluated against the proliferation of ESCC cell lines EC9706 and EC1 by CCK-8 kit and in a mice model of ESCC EC9706. Cell cycle and apoptosis were investigated by flow cytometry, and cell invasion was determined via transwell chamber. Protein expression was examined by Western blots.
Results: We found that C-PC exhibited anti-proliferation ability in a time-dependent manner and a dose-dependent manner in ESCC EC9706 and EC1 cells. Besides, C-PC markedly arrested cell cycle in the G0/G1 phase, induced cell apoptosis and suppressed cell invasion ability in both EC9706 and EC1 cells (p?<?.01). Notably, C-PC evoked the elevations of Bax, PARP, and cleaved-caspase-3 protein, but reduced cyclin D1, CDK4, Bcl-2, MMP-2, and MMP-9 expression levels. Further investigation from in vivo experiment revealed that C-PC displayed significant antitumor efficacy in the xenografted EC9706 model.
Conclusions: Our data presented herein suggest C-PC exerts antitumor efficacy in ESCC. 相似文献
Probiotics and Antimicrobial Proteins - Although the use of the probiotic bacterium Lactobacillus for the treatment and prevention of diseases caused by various pathogenic bacteria has received... 相似文献