Flavonoid content and radical scavenging activity in fruits of Chinese dwarf cherry(Cerasus humilis) genotypes

The Chinese dwarf cherry(Cerasus humilis(Bge.) Sok.) is a small shrub with edible fruits. It is native to northern and western China. This species was included as a medicinal plant in the ‘‘Chinese Pharmacopeia'' and has emerged as an economically important crop for fresh fruit consumption, processing into juice and wine and nutraceutical products as well. To gain a better understanding of flavonoid biosynthesis and help develop value added products and better cultivars with greater health benefits, we analyzed total flavonoid content(TFC), composition, and radical scavenging activities in fruit extracts of 16 Chinese dwarf cherry genotypes. Fruit peel TFC ranged from 33.5 to72.8 mg/g REáFW(RE: rutin equivalent, FW: fresh weight)while fruit flesh TFC ranged from 4.3 to 16.9 mg/g REáFW.An HPLC analysis revealed that fruit extracts contained 14 flavonoids with considerable variation in their profiles across genotypes. The most abundant flavonoids in most genotypes were proanthocyanidin B1(PA-B1), proanthocyanidin B2(PA-B2), phloretin 20-O-glucoside(PG), and phloretin 20,40-O-diglucoside(PDG). Principal component analysis showed that PG, PA-B1, and PA-B2 had large,positive factor loading values in the first principal component for each genotype. Increased scavenging activity of2,2-diphenyl-1-picrylhydrazyl(DPPH) radicals was apparent in genotypes ‘Nongda 4', ‘Nongda 3', ‘Nongda 6',‘Wenfenli', and '10-32', suggesting promising applications in the production of nutraceutical products. In summary, our results will aid in breeding, fruit processing, and developing medicinal uses of the Chinese dwarf cherry.

草地生物多样性与稳定性及对草地保护与修复的启示

草地为人类社会提供了生物多样性保护、水土保持、气候调节、畜牧生产等重要的生态系统服务。在全球变化背景下,草地退化导致了生物多样性丧失,生态系统多功能性下降、稳定性减弱等一系列问题。解析草地生物多样性与稳定性的维持机制,对草地保护与功能提升至关重要。本文系统梳理了草地生物多样性与生产力关系、多营养级生物多样性、生态系统多功能性、生态系统地上—地下互作及生态系统稳定性对全球变化响应等方面的研究进展与发展趋势。结合学术前沿、“生态安全”“双碳”等重大国家需求,本文建议未来应加强新技术新方法在生物多样性跨尺度监测中的应用,深化生物多样性与气候变化研究的融合,研发退化草地的近自然恢复技术,提升草地生物多样性和稳定性,从而为草地生态系统的科学管理和可持续发展提供科技支撑。

Nitrogen addition and mowing alter drought resistance and recovery of grassland communities

Nitrogen enrichment and land use are known to influence various ecosystems,but how these anthropogenic changes influence community and ecosystem responses to disturbance remains poorly understood.Here we investigated the effects of increased nitrogen input and mowing on the resistance and recovery of temperate semiarid grassland experiencing a three-year drought.Nitrogen addition increased grassland biomass recovery but decreased structural recovery after drought,whereas annual mowing increased grassland biomass recovery and structural recovery but reduced structural resistance to drought.The treatment effects on community biomass/structural resistance and recovery were largely modulated by the stability of the dominant species and asynchronous dynamics among species,and the community biomass resistance and recovery were also greatly driven by the stability of grasses.Community biomass resistance/recovery in response to drought was positively associated with its corresponding structural stability.Our study provides important experimental evidence that both nitrogen addition and mowing could substantially change grassland stability in both functional and structural aspects.Our findings emphasize the need to study changes across levels of ecological organization for a more complete understanding of ecosystem responses to disturbances under widespread environmental changes.

氮水添加改变内蒙古典型草原两种优势植物的氮吸收偏好

植物对不同形态氮的吸收直接影响输入到生态系统中氮的去向和氮动态的变化,但是资源添加如何影响植物氮吸收偏好仍不明确.本研究依托内蒙古典型草原连续开展了10年氮、水添加实验平台,选择克氏针茅(Stipa krylovii)和冰草(Agropyron cristatum)两个优势物种为研究对象,使用15N自然丰度法测定植物叶片和土壤各形态氮含量及其同位素特征,利用同位素混合模型量化不同氮源对植物氮的贡献,探究植物氮吸收偏好及其对资源添加的响应.结果表明,(1)自然状态下硝态氮和铵态氮对植物氮的贡献分别约为80%和20%;(2)氮添加减小了两种植物对硝态氮的利用,水分添加降低了克氏针茅而提高了冰草对硝态氮的利用,氮、水处理对植物氮吸收偏好的影响具有显著的交互作用.结果揭示,内蒙古典型草原优势植物在自然状态下主要利用较丰富的硝态氮,对较贫瘠的铵态氮利用较少;并且氮吸收特征随着资源添加而改变,水分对氮吸收的影响受到了氮素供给的调节.未来氮沉降加剧和硝态氮比例增加并非总是产生负效应,很可能促进温带草原优势植物的生长,减缓全球环境变化的生态后果.

Grazing effects on herbage nutritive values depend on precipitation and growing season in Inner Mongolian grassland

Aims Grasslands are widely used for production of livestock,which depend on the nutritive value of herbage species.However,there are still large uncertainties as to how grazing,precipitation and growing season interactively affect herbage nutritive value.Methods Here,based on a grazing experiment with seven grazing intensities in an Inner Mongolian grassland since the year 2005,we analysed nutritive value of four dominant grass species from June to September in both a relatively wetter year(2008)and a drier year(2010).Herbage with high nutritive value is characterized by high concentration of crude protein,high concentration of cellulase digestible organic matter and low concentration of neutral detergent fibre.Important Findings We found that(i)grazing significantly increased the nutritive value of Leymus chinensis,Agropyron michnoi and Cleistogenes squarrosa but had minor effects on the nutritive value of Stipa grandis.(ii)For all species,nutritive values were greater in the wetter year than in the drier year and were greatest in the early growing season(June)and lowest at the end of the growing season(September).Inter-annual and inter-seasonal variations in nutritive value were much greater for L.chinensis and A.michnoi than for C.squarrosa and S.grandis,suggesting higher water use efficiency for the latter two species.(iii)Grazing significantly decreased the drought resistance of three species,but not of S.grandis.(iv)Grazing significantly increased inter-month variation in nutritive value for L.chinensis and A.michnoi but had relatively minor or no effects on that of C.squarrosa and S.grandis.Therefore,grazing effects on species nutritive values showed strong inter-annual and seasonal patterns,and species-specific responses might be related to species traits(i.e.water use efficiency,digestibility).Our results have important implications for ecosystem management of arid and semiarid grasslands under intense grazing and global climatic change.

Mass loss and nutrient dynamics during litter decomposition in response to warming and nitrogen addition in a desert steppe

Plant litter decomposition has been studied extensively in the context of both warming and increased atmospheric nitrogen deposition. However, the temporal patterns of mass loss and nutrient release in response to warming and nitrogen addition remain unclear. A 2-year decomposition experiment aimed to examine the effects of warming and nitrogen addition on decomposition rate, and nitrogen and phosphorus dynamics. The effects of warming and nitrogen addition on decomposition of litter of Stipa breviflora, a dominant species in a desert steppe of northern China, were studied. Warming and nitrogen addition significantly enhanced litter mass loss by 10% and 16%, respectively, and moreover promoted nitrogen and phosphorus release from the litter in the first year of decomposition, followed by an immobilization period. The interactive effects of warming and nitrogen addition on mass loss, nitrogen and phosphorus concentrations of litter were also found during the decomposition. This study indicates that warming and nitrogen addition increased litter mass loss through altering litter quality. These findings highlight that interactions between climate change and other global change factors could be highly important in driving decomposition responses.

氮添加对内蒙古草原植物地上和地下碳氮磷化学计量学特征的影响

氮沉降对生态系统功能和过程具有显著影响。已有研究表明氮添加会影响植物叶片C:N:P化学计量特征。然而,氮添加对植物根系C:N:P化学计量特征影响的研究罕有报道。本论文的主要目的是对比氮添加对草原植物群落地上和地下C:N:P化学计量特征的影响。我们在内蒙古锡林郭勒草原开展了一个7年的氮添加实验,该实验包括6个处理,分别是对照:control;N1:0.4 mol·m-2 N;N2:0.8 mol·m^(-2) N;N3:1.6 mol·m^(-2) N;N4:2.8 mol·m^(-2) N;N5:4 mol·m^(-2) N,每个处理6次重复。我们测量并分析了植物地上、地下生物量和C:N:P化学计量特征。研究结果表明,氮添加会导致植物群落地上部分碳浓度降低,氮浓度和磷浓度升高,C:N和C:P比值降低,N:P升高,而且地上碳、氮、磷库均因施氮而增加。然而,氮添加对0-10,10-30,30-50和50-100 cm 4个土层的地下部分碳、氮、磷浓度、比例、库和化学计量特征没有显著影响。综上所述,氮添加会显著改变植物群落地上部分C:N:P化学计量特征,进而影响草地生态系统的功能和过程,但对地下C:N:P化学计量特征几乎没有影响。

Transfer of disulfide bond formation modules via yeast artificial chromosomes promotes the expression of heterologous proteins inKluyveromyces marxianus

Kluyveromyces marxianus is a food-safe yeast with great potential for producing heterologous proteins.Improving the yield in K.marxianus remains a challenge and incorporating large-scale functional modules poses a technical obstacle in engineering.To address these issues,linear and circular yeast artificial chromosomes of K.marxianus(KmYACs)were constructed and loaded with disulfide bond formation modules from Pichia pastoris or K.marxianus.These modules contained up to seven genes with a maximum size of 15 kb.KmYACs carried telomeres either from K.marxianus or Tetrahymena.KmYACs were transferred successfully into K.marxianus and stably propagated without affecting the normal growth of the host,regardless of the type of telomeres and configurations of KmYACs.KmYACs increased the overall expression levels of disulfide bond formation genes and significantly enhanced the yield of various heterologous proteins.In high-density fermentation,the use of KmYACs resulted in a glucoamylase yield of 16.8 g/l,the highest reported level to date in K.marxianus.Transcriptomic and metabolomic analysis of cells containing KmYACs suggested increased flavin adenine dinucleotide biosynthesis,enhanced flux entering the tricarboxylic acid cycle,and a preferred demand for lysine and arginine as features of cells overexpressing heterologous proteins.Consistently,supplementing lysine or arginine further improved the yield.Therefore,KmYAC provides a powerful platform for manipulating large modules with enormous potential for industrial applications and fundamental research.Transferring the disulfide bond formation module via YACs proves to be an efficient strategy for improving the yield of heterologous proteins,and this strategy may be applied to optimize other microbial cell factories.