Generation of a DMD loss-of-function mutant human embryonic stem cell lines by CRISPR base editing.

Duchenne muscular dystrophy (DMD) is a fatal X-linked recessive disorder, which is caused mostly by frame-disrupting, out-of-frame variation in the dystrophin (DMD) gene. Loss-of- function mutations are the most common type of mutation in DMD, accounting for approximately 60-90% of all DMD variations. In this study, we used adenine base editing to generate a human embryonic stem cell line with splice-site mutations to mimic exon deletion variants in clinical Duchenne muscular dystrophy patients. This cell line has differentiation potential and a normal karyotypic.

The pseudoenzyme ADPRHL1 affects cardiac function by regulating the ROCK pathway.

BACKGROUND: Pseudoenzymes, catalytically deficient variants of active enzymes, have a wide range of regulatory functions. ADP-ribosylhydrolase-like 1 (ADPRHL1), a pseudoenzyme belonging to a small group of ADP-ribosylhydrolase enzymes that lacks the amino acid residues necessary for catalytic activity, may have a significant role in heart development based on accumulating evidence. However, the specific function of ADPRHL1 in this process has not been elucidated. To investigate the role of ADPRHL1 in the heart, we generated the first in vitro human embryonic stem cell model with an ADPRHL1 knockout. METHOD: Using the CRISPR/Cas9 system, we generated ADPRHL1 knockout in the human embryonic stem cell (hESC) H9 line. The cells were differentiated into cardiomyocytes using a chemically defined and xeno-free method. We employed confocal laser microscopy to detect calcium transients and microelectrode array (MEA) to assess the electrophysiological activity of ADPRHL1 deficiency cardiomyocytes. Additionally, we investigated the cellular mechanism of ADPRHL1 by Bulk RNA sequencing and western blot. RESULTS: The results indicate that the absence of ADPRHL1 in cardiomyocytes led to adhered abnormally, as well as perturbations in calcium transients and electrophysiological activity. We also revealed that disruption of focal adhesion formation in these cardiomyocytes was due to an excessive upregulation of the ROCK-myosin II pathway. Notably, inhibition of ROCK and myosin II effectively restores focal adhesions in ADPRHL1-deficient cardiomyocytes and improved electrical conduction and calcium activity. CONCLUSIONS: Our findings demonstrate that ADPRHL1 plays a critical role in maintaining the proper function of cardiomyocytes by regulating the ROCK-myosin II pathway, suggesting that it may serve as a potential drug target for the treatment of ADPRHL1-related diseases.

KCNQ1-deficient and KCNQ1-mutant human embryonic stem cell-derived cardiomyocytes for modeling QT prolongation.

BACKGROUND: The slowly activated delayed rectifier potassium current (IKs) mediated by the KCNQ1 gene is one of the main currents involved in repolarization. KCNQ1 mutation can result in long-QT syndrome type 1 (LQT1). IKs does not participate in repolarization in mice; thus, no good model is currently available for research on the mechanism of and drug screening for LQT1. In this study, we established a KCNQ1-deficient human cardiomyocyte (CM) model and performed a series of microelectrode array (MEA) detection experiments on KCNQ1-mutant CMs constructed in other studies to explore the pathogenic mechanism of KCNQ1 deletion and mutation and perform drug screening. METHOD: KCNQ1 was knocked out in human embryonic stem cell (hESC) H9 line using the CRISPR/cas9 system. KCNQ1-deficient and KCNQ1-mutant hESCs were differentiated into CMs through a chemically defined differentiation protocol. Subsequently, high-throughput MEA analysis and drug intervention were performed to determine the electrophysiological characteristics of KCNQ1-deficient and KCNQ1-mutant CMs. RESULTS: During high-throughput MEA analysis, the electric field potential and action potential durations in KCNQ1-deficient CMs were significantly longer than those in wild-type CMs. KCNQ1-deficient CMs also showed an irregular rhythm. Furthermore, KCNQ1-deficient and KCNQ1-mutant CMs showed different responses to different drug treatments, which reflected the differences in their pathogenic mechanisms. CONCLUSION: We established a human CM model with KCNQ1 deficiency showing a prolonged QT interval and an irregular heart rhythm. Further, we used various drugs to treat KCNQ1-deficient and KCNQ1-mutant CMs, and the three models showed different responses to these drugs. These models can be used as important tools for studying the different pathogenic mechanisms of KCNQ1 mutation and the relationship between the genotype and phenotype of KCNQ1, thereby facilitating drug development.

Ranolazine rescues the heart failure phenotype of PLN-deficient human pluripotent stem cell-derived cardiomyocytes.

Phospholamban (PLN) is a key regulator that controls the function of the sarcoplasmic reticulum (SR) and is required for the regulation of cardiac contractile function. Although PLN-deficient mice demonstrated improved cardiac function, PLN loss in humans can result in dilated cardiomyopathy (DCM) or heart failure (HF). The CRISPR-Cas9 technology was used to create a PLN knockout human induced pluripotent stem cell (hiPSC) line in this study. PLN deletion hiPSCs-CMs had enhanced contractility at day 30, but proceeded to a cardiac failure phenotype at day 60, with decreased contractility, mitochondrial damage, increased ROS production, cellular energy metabolism imbalance, and poor Ca2+ handling. Furthermore, adding ranolazine to PLN knockout hiPSCs-CMs at day 60 can partially restore Ca2+ handling disorders and cellular energy metabolism, alleviating the PLN knockout phenotype of HF, implying that the disorder of intracellular Ca2+ transport and the imbalance of cellular energy metabolism are the primary mechanisms for PLN deficiency pathogenesis.

Generation of a homozygous S100A1 knockout human embryonic stem cell line (WAe009-A-73) by the CRISPR/Cas9 editing system.

S100A1 is a calcium-binding protein involved in myocardial contractility,which possesses a high affinity for calcium.  Several studies have demonstrated that S100A1 is a protector against myocardial injury. In this study, we have generated a homozygous S100A1 knockout (S100A1-KO) human embryonic stem cell (hESC) line by the CRISPR/Cas9 editing system. This S100A1-KO hESC line maintained normal morphology, pluripotency and karyotype, which can differentiate into three germ layers in vivo.

Generation of a homozygous MYH7 gene knockout human embryonic stem cell line (WAe009-A-69) using an episomal vector-based CRISPR/Cas9 system.

Myosin heavy chain 7 (MYH7) encodes the human heart myosin heavy chain subunit, which plays an important role in myocardial contraction. MYH7 is the main pathogenic gene that causes Hypertrophic cardiomyopathy (HCM) and Dilated cardiomyopathy (DCM). In this experiment, a MYH7 homozygous knockout human embryonic stem cell (hESC) line, WAe009-A-69, was generated using an episomal vector-based CRISPR/Cas9 system. It can be an ideal tool to further study the function of MYH7. The cell line was confirmed with pluripotency, normal karyotype and trilineage differentiation potential.

hERG-deficient human embryonic stem cell-derived cardiomyocytes for modelling QT prolongation.

BACKGROUND: Long-QT syndrome type 2 (LQT2) is a common malignant hereditary arrhythmia. Due to the lack of suitable animal and human models, the pathogenesis of LQT2 caused by human ether-a-go-go-related gene (hERG) deficiency is still unclear. In this study, we generated an hERG-deficient human cardiomyocyte (CM) model that simulates 'human homozygous hERG mutations' to explore the underlying impact of hERG dysfunction and the genotype-phenotype relationship of hERG deficiency. METHODS: The KCNH2 was knocked out in the human embryonic stem cell (hESC) H9 line using the CRISPR/Cas9 system. Using a chemically defined differentiation protocol, we obtained and verified hERG-deficient CMs. Subsequently, high-throughput microelectrode array (MEA) assays and drug interventions were performed to characterise the electrophysiological signatures of hERG-deficient cell lines. RESULTS: Our results showed that KCNH2 knockout did not affect the pluripotency or differentiation efficiency of H9 cells. Using high-throughput MEA assays, we found that the electric field potential duration and action potential duration of hERG-deficient CMs were significantly longer than those of normal CMs. The hERG-deficient lines also exhibited irregular rhythm and some early afterdepolarisations. Moreover, we used the hERG-deficient human CM model to evaluate the potency of agents (nifedipine and magnesium chloride) that may ameliorate the phenotype. CONCLUSIONS: We established an hERG-deficient human CM model that exhibited QT prolongation, irregular rhythm and sensitivity to other ion channel blockers. This model serves as an important tool that can aid in understanding the fundamental impact of hERG dysfunction, elucidate the genotype-phenotype relationship of hERG deficiency and facilitate drug development.

Cell sheet formation enhances the therapeutic effects of human umbilical cord mesenchymal stem cells on myocardial infarction as a bioactive material.

Stem cell-based therapy has been used to treat ischaemic heart diseases for two decades. However, optimal cell types and transplantation methods remain unclear. This study evaluated the therapeutic effects of human umbilical cord mesenchymal stem cell (hUCMSC) sheet on myocardial infarction (MI). METHODS: hUCMSCs expressing luciferase were generated by lentiviral transduction for in vivo bio-luminescent imaging tracking of cells. We applied a temperature-responsive cell culture surface-based method to form the hUCMSC sheet. Cell retention was evaluated using an in vivo bio-luminescent imaging tracking system. Unbiased transcriptional profiling of infarcted hearts and further immunohistochemical assessment of monocyte and macrophage subtypes were used to determine the mechanisms underlying the therapeutic effects of the hUCMSC sheet. Echocardiography and pathological analyses of heart sections were performed to evaluate cardiac function, angiogenesis and left ventricular remodelling. RESULTS: When transplanted to the infarcted mouse hearts, hUCMSC sheet significantly improved the retention and survival compared with cell suspension. At the early stage of MI, hUCMSC sheet modulated inflammation by decreasing Mcp1-positive monocytes and CD68-positive macrophages and increasing Cx3cr1-positive non-classical macrophages, preserving the cardiomyocytes from acute injury. Moreover, the extracellular matrix produced by hUCMSC sheet then served as bioactive scaffold for the host cells to graft and generate new epicardial tissue, providing mechanical support and routes for revascularsation. These effects of hUCMSC sheet treatment significantly improved the cardiac function at days 7 and 28 post-MI. CONCLUSIONS: hUCMSC sheet formation dramatically improved the biological functions of hUCMSCs, mitigating adverse post-MI remodelling by modulating the inflammatory response and providing bioactive scaffold upon transplantation into the heart. TRANSLATIONAL PERSPECTIVE: Due to its excellent availability as well as superior local cellular retention and survival, allogenic transplantation of hUCMSC sheets can more effectively acquire the biological functions of hUCMSCs, such as modulating inflammation and enhancing angiogenesis. Moreover, the hUCMSC sheet method allows the transfer of an intact extracellular matrix without introducing exogenous or synthetic biomaterial, further improving its clinical applicability.

Microscale grooves regulate maturation development of hPSC-CMs by the transient receptor potential channels (TRP channels).

The use of human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) is limited in drug discovery and cardiac disease mechanism studies due to cell immaturity. Micro-scaled grooves can promote the maturation of cardiomyocytes by aligning them in order, but the mechanism of cardiomyocytes alignment has not been studied. From the level of calcium activity, gene expression and cell morphology, we verified that the W20H5 grooves can effectively promote the maturation of cardiomyocytes. The transient receptor potential channels (TRP channels) also play an important role in the maturation and development of cardiomyocytes. These findings support the engineered hPSC-CMs as a powerful model to study cardiac disease mechanism and partly mimic the myocardial morphological development. The important role of the TRP channels in the maturation and development of myocardium is first revealed.

The establishment of a homozygous SNTA1 knockout human embryonic stem cell line (WAe009-A-50) using the CRISPR/Cas9 system.

SNTA1 encodes α1-syntrophin, a scaffold protein, which is a component of the dystrophin-associated protein complex. Additionally, α1-syntrophin interacts with SCN5A and nNOS-PMCA4b complex in cardiomyocytes. SNTA1 is a susceptibility locus for arrhythmia and cardiomyopathy. We generated a homozygous SNTA1 knockout human embryonic stem cell (H9SNTA1KO) using the CRISPR/Cas9 system. H9SNTA1KO maintained pluripotency and a normal karyotype and differentiated into three germ layers in vivo.

Ascorbic acid can promote the generation and expansion of neuroepithelial-like stem cells derived from hiPS/ES cells under chemically defined conditions through promoting collagen synthesis.

INTRODUCTION: Spinal cord injury (SCI) is a neurological, medically incurable disorder. Human pluripotent stem cells (hPSCs) have the potential to generate neural stem/progenitor cells (NS/PCs), which hold promise in the treatment of SCI by transplantation. In our study, we aimed to establish a chemically defined culture system using serum-free medium and ascorbic acid (AA) to generate and expand long-term self-renewing neuroepithelial-like stem cells (lt-NES cells) differentiated from hPSCs effectively and stably. METHODS: We induced human embryonic stem cells (hESCs)/induced PSCs (iPSCs) to neurospheres using a newly established in vitro induction system. Moreover, lt-NES cells were derived from hESC/iPSC-neurospheres using two induction systems, i.e., conventional N2 medium with gelatin-coated plates (coated) and N2+AA medium without pre-coated plates (AA), and were characterized by reverse transcription polymerase chain reaction (RT-PCR) analysis and immunocytochemistry staining. Subsequently, lt-NES cells were induced to neurons. A microelectrode array (MEA) recording system was used to evaluate the functionality of the neurons differentiated from lt-NES cells. Finally, the mechanism underlying the induction of lt-NES cells by AA was explored through RNA-seq and the use of inhibitors. RESULTS: HESCs/iPSCs were efficiently induced to neurospheres using a newly established induction system in vitro. lt-NES cells derived from hESC/iPSC-neurospheres using the two induction systems (coated vs. AA) both expressed the neural pluripotency-associated genes PAX6, NESTIN, SOX1, and SOX2. After long-term cultivation, we found that they both exhibited long-term expansion for more than a dozen generations while maintaining neuropluripotency. Moreover, the lt-NES cells retained the ability to differentiate into general functional neurons that express ß-tubulin at high levels. We also demonstrated that AA promotes the generation and long-term expansion of lt-NES cells by promoting collagen synthesis via the MEK-ERK1/2 pathway. CONCLUSIONS: This new chemically defined culture system was stable and effective regarding the generation and culture of lt-NES cells induced from hESCs/iPSCs using serum-free medium combined with AA. The lt-NES cells induced under this culture system maintained their long-term expansion and neural pluripotency, with the potential to differentiate into functional neurons.

Determinants of post-fire regeneration demography in a subtropical monsoon-climate forest in Southwest China.

Understanding the determinants of post-fire regeneration is critical for determining an appropriate restoration program following fire disturbances. However, studies addressing the drivers of post-fire regeneration of forests in monsoon climate are rare. This study explored the temporal and spatial variations of post-fire forest regeneration in the Central Yunnan Plateau of Southwest China, and disentangled the direct and indirect effects of the environmental factors via structural equation models (SEMs). We found that the overall post-fire regeneration density was generally greater for the habitat with higher values of elevation, pre-fire abundance, and soil pH. Post-fire regeneration was mainly composed of resprouts; seedlings were less relevant and appeared later. The SEM approach showed more variation of recruitment in resprouting (R2 = 0.66) than seeding (R2 = 0.33), and revealed different direct and indirect pathways. Resprouts were widely distributed, and significantly influenced by pre-fire abundance, elevation, soil pH, and years since the last fire. In contrast, seedlings preferentially occurred in infertile habitats, and were mainly influenced by topographic position and soil nutrients, showing distinct distribution from that of resprouts. Overall, forests under the subtropical monsoon climate in the Central Yunnan Plateau were resilient to fire mainly due to rapid post-fire resprouting. These findings indicate the complementary roles of resprouting and seeding in post- fire regeneration, and help to understand the mechanisms that regulate post-fire plant regeneration in a spatially heterogeneous landscape. Our results should contribute to improving the post-fire management of forest ecosystems under the influence of a semi-humid monsoon climate.

Increasing water availability and facilitation weaken biodiversity-biomass relationships in shrublands.

Positive biodiversity-ecosystem-functioning (BEF) relationships are commonly found in experimental and observational studies, but how they vary in different environmental contexts and under the influence of coexisting life forms is still controversial. Investigating these variations is important for making predictions regarding the dynamics of plant communities and carbon pools under global change. We conducted this study across 433 shrubland sites in northern China. We fitted structural equation models (SEMs) to analyze the variation in the species-richness-biomass relationships of shrubs and herbs along a wetness gradient and general liner models (GLMs) to analyze how shrub or herb biomass affected the species-richness-biomass relationship of the other life form. We found that the positive species-richness-biomass relationships for both shrubs and herbs became weaker or even negative with higher water availability, likely indicating stronger interspecific competition within life forms under more benign conditions. After accounting for variation in environmental contexts using residual regression, we found that the benign effect of greater facilitation by a larger shrub biomass reduced the positive species-richness-biomass relationships of herbs, causing them to become nonsignificant. Different levels of herb biomass, however, did not change the species-richness-biomass relationship of shrubs, possibly because greater herb biomass did not alter the stress level for shrubs. We conclude that biodiversity in the studied plant communities is particularly important for plant biomass production under arid conditions and that it might be possible to use shrubs as nurse plants to facilitate understory herb establishment in ecological restoration.

Legume Shrubs Are More Nitrogen-Homeostatic than Non-legume Shrubs.

Legumes are characterized as keeping stable nutrient supply under nutrient-limited conditions. However, few studies examined the legumes' stoichiometric advantages over other plants across various taxa in natural ecosystems. We explored differences in nitrogen (N) and phosphorus (P) stoichiometry of different tissue types (leaf, stem, and root) between N2-fixing legume shrubs and non-N2-fixing shrubs from 299 broadleaved deciduous shrubland sites in northern China. After excluding effects of taxonomy and environmental variables, these two functional groups differed considerably in nutrient regulation. N concentrations and N:P ratios were higher in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated between the plants and soil for non-N2-fixing shrubs, but not for legume shrubs, indicating a stronger stoichiometric homeostasis in legume shrubs than in non-N2-fixing shrubs. N concentrations were positively correlated among three tissue types for non-N2-fixing shrubs, but not between leaves and non-leaf tissues for legume shrubs, demonstrating that N concentrations were more dependent among tissues for non-N2-fixing shrubs than for legume shrubs. N and P concentrations were correlated within all tissues for both functional groups, but the regression slopes were flatter for legume shrubs than non-N2-fixing shrubs, implying that legume shrubs were more P limited than non-N2-fixing shrubs. These results address significant differences in stoichiometry between legume shrubs and non-N2-fixing shrubs, and indicate the influence of symbiotic nitrogen fixation (SNF) on plant stoichiometry. Overall, N2-fixing legume shrubs are higher and more stoichiometrically homeostatic in N concentrations. However, due to excess uptake of N, legumes may suffer from potential P limitation. With their N advantage, legume shrubs could be good nurse plants in restoration sites with degraded soil, but their P supply should be taken care of during management according to our results.

Hotspot analyses indicate significant conservation gaps for evergreen broadleaved woody plants in China.

Evergreen broadleaved woody plants (EBWPs) are dominant components in forests and savanna of the global tropic and subtropic regions. Southern China possesses the largest continuous area of subtropical EBWPs distribution, harboring a high proportion of endemic species. Hotspot and gap analyses are effective methods for analyzing the spatial pattern of biodiversity and conservation and were used here for EBWPs in China. Based on a distribution data set of 6,265 EBWPs with a spatial resolution of 50 × 50 km, we measured diversity of EBWPs in China using four indices: species richness, corrected weighted endemism, relative phylogenetic diversity, and phylogenetic endemism. According to the results based on 10% threshold, 15.73% of China's land area was identified as hotspots using at least one diversity index. Only 2.14% of China's land area was identified as hotspots for EBWPs by all four metrics simultaneously. Most of the hotspots locate in southern mountains. Moreover, we found substantial conservation gaps for Chinese EBWPs. Only 25.43% of the hotspots are covered by existing nature reserves by more than 10% of their area. We suggest to promote the establishment and management of nature reserve system within the hotspot gaps.

Influence of HMGB1 and MSCs transplantation on rat cardiac angiogenesis with acute myocardial infarction.

To observe whether HMGB1could enhance the paracrine effect of MSCs when the Mesenchymal stem cells (Mesenchymal stem cells, MSCs) are pre-proccessed by High Mobility Group Box-1 (High Mobility Group Box-1, HMGB1). And to observe whether it can further increase the quantity of local angiogenesis in myocardial infarcts on the rat model with acute myocardial infarction, HMGB1 was combined with MSCs transplantation. MSCs in rats were cultivated with adherence and centrifugation method. Receptors of TLR4and RAGE in HMGB1 were tested. The MSCs were interfered by HMGB1 with different concentration gradient respectively, then the expression of VEGF was tested with ELISA method. SD male rats were divided into four groups: the model group, the MSCs transplantation group, the HMGB1 injection group, the HMGB1 injection plus MSCs transplantation group (n = 24), preparing rat model with acute myocardial infarction. The serum VEGF concentration levels were detected on the 3rd day, 7th and 28th day with ELISA method. On the 28th day after post operation the density of angiogenesis in infarction area was detected by immunohistochemal. (1) MSCs owned the expression of TLR4 and RAGE. (2) the secretion of VEGF increased significantly after the intervention of HMGB1 with concentration of 12.5 ng/mL, 25 ng/mL, 50 ng/mL, 100 ng/mL and 200ng/ml on MSCs compared with the control group. While the concentration was 400ng/ml or 800ng/ml, the secretion of VEGF decreased compared with the control group (P < 0.05). (3) detection of the serum VEGF on the 3rd or7th day after post operation was arranged: The results showed that: HMGB1 injection plus MSCs transplantation group > MSCs transplantation group >HMGB1 injection group >model group (P < 0.05). (4) the quantity of CD31 stained angiogenesis in HMGB1 injection plus MSCs transplantation group increased obviously. Combining MSCs transplantation, contributed to new angiogenesis of rats with acute myocardial infarction in myocardial infarction area and its near area in rats with acute myocardial infarction.

Knockdown of SCARA5 inhibits PDGF-BB-induced vascular smooth muscle cell proliferation and migration through suppression of the PDGF signaling pathway.

Vascular smooth muscle cell (VSMC) proliferation and migration are critical in the progression of atherosclerosis and can be induced by platelet-derived growth factor (PDGF). Several studies have demonstrated that scavenger receptor class A, member 5 (SCARA5) is important in cancer cell migration and invasion. However, the role of SCARA5 in VSMCs remains to be elucidated in the development of atherosclerosis. Therefore, the role of SCARA5 was investigated in PDGF­BB­stimulated VSMC proliferation and migration. In the present study, it was shown that SCARA5 expression was enhanced by PDGF­BB in human aortic smooth muscle cells (HASMCs). Knockdown of SCARA5 by small interfering (si)RNA significantly inhibited PDGF­BB­induced HASMC proliferation and migration. Furthermore, siRNA­SCARA5 significantly inhibited the phosphorylation of PDGF receptor (PDGFR) ß, AKT and extracellular signal­regulated kinase 1/2 in PDGF­BB­stimulated HASMCs. In conclusion, this study demonstrated that knockdown of SCARA5 inhibits PDGF­BB­induced HASMC proliferation and migration through suppression of the PDGF signaling pathway. Thus, SCARA5 may be a novel therapeutic target for preventing or treating vascular diseases involving VSMC proliferation and migration.

The links between ecosystem multifunctionality and above- and belowground biodiversity are mediated by climate.

Plant biodiversity is often correlated with ecosystem functioning in terrestrial ecosystems. However, we know little about the relative and combined effects of above- and belowground biodiversity on multiple ecosystem functions (for example, ecosystem multifunctionality, EMF) or how climate might mediate those relationships. Here we tease apart the effects of biotic and abiotic factors, both above- and belowground, on EMF on the Tibetan Plateau, China. We found that a suite of biotic and abiotic variables account for up to 86% of the variation in EMF, with the combined effects of above- and belowground biodiversity accounting for 45% of the variation in EMF. Our results have two important implications: first, including belowground biodiversity in models can improve the ability to explain and predict EMF. Second, regional-scale variation in climate, and perhaps climate change, can determine, or at least modify, the effects of biodiversity on EMF in natural ecosystems.

Nitrogen dynamics differed among the first six root branch orders of Fraxinus mandshurica and Larix gmelinii during short-term decomposition.

Fine root (<2 mm) decomposition provides a substantial amount of available nitrogen (N) that sustains plant growth. The N release pattern during litter decomposition is generally controlled by initial N concentrations or C/N. Because root branch order and mycorrhizal colonization (related with branch order) are both highly related with different initial chemistry, a hypothesis was proposed that N dynamics during root decomposition varied among different branch orders. Using the litterbag method, decomposition of the first six order roots for Fraxinus mandshurica (an arbuscular mycorrhizal species) and Larix gmelinii (an ectomycorrhizal species) was studied in Northeast China during a 513-day period. Results showed a similar pattern for the two species with contrasting mycorrhizal type: lower-order roots (the lateral root tips), which had an initial C/N of 17-21, continuously released N without any immobilization and maintained a consistently low C/N (<20), whereas higher-order roots, which had an initial C/N of 28-48, periodically immobilized N, leading to a declining C/N over time. In addition, the magnitude of N dynamics is different between species for lower-order roots, but no different for higher-order roots. These results suggest that fine root N dynamics are heterogeneous among branch orders and that species-specific differences depend on the behavior of lower-order roots.

Threat and management strategies of potentially invasive insects in China.

The Global Invasive Species Database, GISD, comprises 27 species of the most significant invasive alien insects in the world (through November, 2005), 6 of which are originally native to China, 11 are established in China, and 10 have a potential invasion threat to China. This paper discusses these species in terms of distribution, harmfulness and dispersal ways, and finds that: (i) Information regarding invasive insects in the GISD remains inadequate. Such harmful invasive species as Opogona sacchari (Bojer), Oracella acuta (Lobdell), and Dendroctonus valens LeConte are not included. (ii) Ten species of invasive insects, particularly Lasius neglectus Van Loon and Linepithema humile (Mayr) which become established in areas near China, have the potential to become established in China. (iii) Special attention should be paid to species from Asia and the Americas because of their greater likelihood of becoming established in China. Finally, some management strategies including legislation, quarantine, early warning, prevention and control are suggested.