Threshold responses of riverine fish communities to land use conversion across regions of the world

The growing human enterprise has sparked greater interest in identifying ecological thresholds in land use conversion beyond which populations or communities demonstrate abrupt nonlinear or substantive change in species composition. Such knowledge remains fundamental to understanding ecosystem resilience to environmental degradation and informing land use planning into the future. Confronting this challenge has been largely limited to inferring thresholds in univariate metrics of species richness and indices of biotic integrity and has largely ignored how land use legacies of the past may shape community responses of today. By leveraging data for 13,069 riverine sites from temperate, subtropical, and boreal climate zones on four continents, we characterize patterns of community change along diverse gradients of urbanization and agricultural land use, and identity threshold values beyond which significant alterations in species composition exists. Our results demonstrate the apparent universality by which freshwater fish communities are sensitive to even low levels of watershed urbanization (range of threshold values: 1%–12%), but consistently higher (and more variable) levels of agricultural development (2%–37%). We demonstrated that fish community compositional thresholds occurred, in general, at lower levels of watershed urbanization and agriculture when compared to threshold responses in species richness. This supports the notion that aggregated taxon‐specific responses may better reflect the complexity of assemblage responses to land use development. We further revealed that the ghost of land use past plays an important role in moderating how current‐day fish communities respond to land use intensification. Subbasins of the United States experiencing greater rates of past land use change demonstrated higher current‐day thresholds. Threshold responses of community composition, such as those identified in our study, illustrate the need for globally coordinated efforts to prioritize country‐specific management and policy initiatives that ensure that freshwater fish diversity is not inevitably lost in the future.     

Ultra‐high α‐linolenic acid accumulating developmental defective embryo was rescued by lysophosphatidic acid acyltransferase 2

For decades, genetic engineering approaches to produce unusual fatty acids (UFAs) in crops has reached a bottleneck, including reduced seed oil production and seed vigor. Currently, plant models in the field of research are primarily used to investigate defects in oil production and seedling development, while the role of UFAs in embryonic developmental defects remains unknown. In this study, we developed a transgenic Arabidopsis plant model, in which the embryo exhibits severely wrinkled appearance owing to α‐linolenic acid (ALA) accumulation. RNA‐sequencing analysis in the defective embryo suggested that brassinosteroid synthesis, FA synthesis and photosynthesis were inhibited, while FA degradation, endoplasmic reticulum stress and oxidative stress were activated. Lipidomics analysis showed that ultra‐accumulated ALA is released from phosphatidylcholine as a free FA in cells, inducing severe endoplasmic reticulum and oxidative stress. Furthermore, we identified that overexpression of lysophosphatidic acid acyltransferase 2 rescued the defective phenotype. In the rescue line, the pool capacity of the Kennedy pathway was increased, and the esterification of ALA indirectly to triacylglycerol was enhanced to avoid stress. This study provides a plant model that aids in understanding the molecular mechanism of embryonic developmental defects and generates strategies to produce higher levels of UFAs.     

Ptr1 evolved convergently with RPS2 and Mr5 to mediate recognition of AvrRpt2 in diverse solanaceous species

The Ptr1 (Pseudomonas tomato race 1) locus in Solanum lycopersicoides confers resistance to strains of Pseudomonas syringae pv. tomato expressing AvrRpt2 and Ralstonia pseudosolanacearum expressing RipBN. Here we describe the identification and phylogenetic analysis of the Ptr1 gene. A single recombinant among 585 F2 plants segregating for the Ptr1 locus was discovered that narrowed the Ptr1 candidates to eight nucleotide‐binding leucine‐rich repeat protein (NLR)‐encoding genes. From analysis of the gene models in the S. lycopersicoides genome sequence and RNA‐Seq data, two of the eight genes emerged as the strongest candidates for Ptr1. One of these two candidates was found to encode Ptr1 based on its ability to mediate recognition of AvrRpt2 and RipBN when it was transiently expressed with these effectors in leaves of Nicotiana glutinosa. The ortholog of Ptr1 in tomato and in Solanum pennellii is a pseudogene. However, a functional Ptr1 ortholog exists in Nicotiana benthamiana and potato, and both mediate recognition of AvrRpt2 and RipBN. In apple and Arabidopsis, recognition of AvrRpt2 is mediated by the Mr5 and RPS2 proteins, respectively. Phylogenetic analysis places Ptr1 in a distinct clade compared with Mr5 and RPS2, and it therefore appears to have arisen by convergent evolution for recognition of AvrRpt2.     

Overexpression of the persimmon abscisic acid β‐glucosidase gene (DkBG1) alters fruit ripening in transgenic tomato

β‐Glucosidases (BG) are present in many plant tissues. Among these, abscisic acid (ABA) β‐glucosidases are thought to take part in the adjustment of cellular ABA levels, however the role of ABA‐BG in fruits is still unclear. In this study, through RNA‐seq analysis of persimmon fruit, 10 full‐length DkBG genes were isolated and were all found to be expressed. In particular, DkBG1 was highly expressed in persimmon fruits with a maximum expression 95 days after full bloom (DAFD). We verified that, in vitro, DkBG1 protein can hydrolyze ABA‐glucose ester (ABA‐GE) to release free ABA. Compared with wild‐type, tomato plants that overexpressed DkBG1 significantly upregulated the expression of ABA receptor PYL3/7 genes and showed typical symptoms of ABA hypersensitivity in fruits. DkBG1 overexpression (DkBG1‐OE) accelerated fruit ripening onset by 3–4 days by increasing ABA levels at the pre‐breaker stage and induced early ethylene release compared with wild‐type fruits. DkBG1‐OE altered the expression of ripening regulator NON‐RIPENING (NOR) and its target genes; this in turn altered fruit quality traits such as coloration. Our results demonstrated that DkBG1 plays an important role in fruit ripening and quality by adjusting ABA levels via hydrolysis of ABA‐GE.     

锌指蛋白ZFP580在全反式维甲酸调节大鼠血管平滑肌细胞迁移中的作用及机制

目的:探讨锌指基因ZFP580在全反式维甲酸(ATRA)调节VSMCs迁移功能中的作用及其机制。方法:分离,培养并鉴定大鼠主动脉VSMCs;分别予以0、5、10、20 μmol/L ATRA刺激VSMCs 24h,以0 μmol/L ATRA组为对照组,观察不同溶度ATRA刺激不同时间对VSMCs迁移能力的影响或给予0、20 μmol/L ATRA刺激VSMCs 24、48、72h,观察ATRA刺激不同时间对VSMCs迁移能力的影响;QPCR及Western blot检测ATRA刺激VSMCs后ZFP580的mRNA和蛋白表达变化;应用ERK抑制剂PD98059抑制ERK的蛋白表达,观察ERK信号蛋白表达变化对ATRA刺激后ZFP580蛋白表达的影响;腺病毒转染技术获得过表达或低表达ZFP580的VSMCs,QPCR及Western blot检测MMP-2和MMP-9、ZFP580蛋白和mRNA表达水平。结果:分离的VSMCs在培养10d后,免疫荧光显示平滑肌细胞特异性标记物SM22α抗体阳性。与对照组相比,5、10、20 μmol/L ATRA预刺激分别降低了32%、43%和59%的VSMCs迁移能力;20 μmol/L ATRA刺激VSMCs与对照组相比,在24、48、72h分别降低49%、36%和22%细胞迁移能力。ZFP580的mRNA和蛋白表达随着ATRA刺激溶度的增加和刺激时间的延长而升高。ERK在ATRA刺激15min即显著升高,运用ERK抑制剂PD98059(20 μmol/L)预处理抑制ERK蛋白表达并降低了ATRA诱导ZFP580的蛋白表达。过表达ZFP580降低MMP-2和MMP-9的mRNA和蛋白表达,反之,低表达ZFP580则上调了MMP-2和MMP-9的mRNA和蛋白表达。结论:ATRA可通过ERK信号通路上调ZFP580的表达,而ZFP580通过调控MMP-2和MMP-9的表达参与ATRA对VSMCs迁移的抑制作用。     

澜沧江流域水生昆虫群落分类多样性和功能多样性海拔格局的空间尺度依赖性

群落分类多样性和功能多样性的海拔格局研究, 是了解生物多样性空间分布现状、揭示多样性维持和变化机制的重要途径。当前对水生昆虫分类多样性和功能多样性沿海拔梯度分布格局, 及其尺度依赖性依旧缺乏深入研究。本文基于2013-2018年在云南澜沧江流域500-3,900 m海拔梯度共149个溪流点位的水生昆虫群落调查数据, 利用线性或二次回归模型探索并比较了局部尺度(点位尺度)和不同区域尺度(100 m、150 m、200 m、250 m海拔段)的分类多样性指数(物种丰富度指数、Simpson多样性指数和物种均匀度指数)和功能多样性指数(树状图功能多样性指数(dbFD)、Rao二次熵指数(RaoQ)和功能均匀度指数(FEve))的海拔格局。结果表明, 在局部尺度, 物种丰富度指数和dbFD指数沿海拔梯度均无显著分布特征, Simpson多样性指数、RaoQ指数、物种均匀度指数和FEve指数沿海拔梯度呈现U型或者单调递减趋势。在区域尺度, 随着区域海拔带宽度的增加, 物种丰富度指数沿海拔呈不显著的单调递减格局, 但dbFD指数沿海拔分布由U型转变为单调递减趋势; Simpson多样性指数和RaoQ指数沿海拔梯度由显著U型趋势转变为无显著分布特征; 物种均匀度指数沿海拔梯度无显著分布特征, 但FEve指数呈显著增加的海拔格局。综上, 群落分类多样性指数和功能多样性指数沿海拔梯度分布存在局部和区域尺度的空间差异, 但区域尺度下二者海拔格局随海拔带宽度的增加存在一定程度的一致性。     

中国科学院清原森林生态系统观测研究站塔群平台的功能和应用

森林生态系统结构与生态服务功能关系是森林生态学和林学的永恒研究主题。受传统森林调查方法及技术手段的限制,对复杂地形下森林生态系统结构和功能的监测及二者关系的研究面临诸多挑战。在中国科学院野外站网络重点科技基础设施建设项目的支持下,中国科学院清原森林生态系统观测研究站在独立流域内建成了以观测塔群(三座观测塔覆盖各自子流域代表性森林类型)为主体,集激光雷达(LiDAR)、通量仪器、水文站网、固定标准地和数据中心为综合体的“次生林生态系统塔群激光雷达监测平台”(简称塔群平台)。塔群平台采用激光雷达扫描获取森林点云数据,描述森林生态系统的全息三维结构;依托独立流域/子流域内的通量监测系统、水文监测站网和通量源区内的长期固定标准地,可保证碳-水过程观测的可靠性,并用于验证复杂地形下的通量监测技术与方法,揭示森林生态水文与碳交换过程,准确估算森林生态系统主体生态服务功能(水源涵养和固碳)。所有“塔-站”数据通过无线网络实时汇集于数据中心,便于数据监视、管理与共享。此外,塔群平台将侧重研究森林生态系统结构量化的新方法和新指标,探索复杂地形森林生态系统中H₂O/CO₂/痕量气体通量观测的理论与方法,为阐明森林结构与功能的关系、服务于森林生态系统管理提供基础数据。     

青藏高原多年冻土区不同水分条件的高寒草甸根系功能性状对增温的响应

在青藏高原多年冻土广泛分布的风火山地区,选择小嵩草（Kobresia pygmea）草甸和藏嵩草（Kobresia tibetica）沼泽化草甸为研究对象,采用开顶增温室（Open top chambers, OTCs）模拟气候变暖,探讨模拟增温对土壤水分差异的两种草甸地下生物量及根系功能性状的影响。结果显示,（1）增温显著增加小嵩草草甸0—20 cm根系生物量,主要是由于表层（0—10 cm）根系生物量显著增加,而对藏嵩草沼泽化草甸根系生物量无影响。（2）增温显著增加了小嵩草草甸根组织密度,同时提高了藏嵩草沼泽化草甸10—20 cm的比根长和比根面积（3）增温降低了小嵩草草甸的根系碳含量及10—20 cm根系氮含量,增加了藏嵩草沼泽化草甸的碳含量及10—20 cm根系氮含量,显著提高了小嵩草草甸和藏嵩草沼泽化草甸深层（10—20 cm）根系碳氮比。这些结果预示着增温使得土壤水分较低的小嵩草草甸朝着资源保守的慢速生长型发展,以适应暖干化的环境;土壤水分较高的藏嵩草沼泽化草甸朝着资源获取的快速生长型发展,加速利用土壤中的养分满足植物生长需要。可见,土壤水分可以调节高寒草甸对气候变暖的演变趋势,强调了水分的重要性。     

全球气候治理新进展——区域碳排放权分配研究综述

碳排放权作为稀缺的公共资源,其实质是一种新型发展权。科学合理分配有限的碳排放权对实现《巴黎协定》温控目标至关重要。从原则、方法、尺度与方案等维度对碳排放权分配的文献成果进行了系统梳理与归纳。研究表明,国内外学者大多基于公平性和效率性原则探索碳排放权分配;分配方法分为指标法、博弈论法、数据包络分析法和综合法等,各有利弊和适用条件;分配尺度大多涉及国际和区际两个层面,前者由于各国不同的利益诉求较难形成共识性方案,后者主要关注省际分配,更小尺度的研究相对较少。未来碳排放权分配研究趋向于多原则兼顾、多方法联用,涵盖国际、省际、市际及行业、企业等不同尺度。本研究可为制定科学合理的碳排放权分配方案提供理论依据,为我国更为积极有效地参与全球气候治理提供决策参考。