栲树种群的年龄结构及其生长特征

为了了解栲树的更新方式和更新动态,研究了栲树的生长特征和种群年龄结构.结果表明：栲树种群的年龄结构呈“间歇型”,经历了两个死亡高峰,并存在一个长达30年的断层;栲树的生长受光照的影响,具有很强的可塑性;由于林下光照弱且在垂直空间上不存在差异,栲树生长5～8年后进入生长的第1个抑制期,其年高生长速度可小于0.1 m,并可维持10年;栲树生长的第1个抑制期的起始时间对应着种群第1个死亡高峰期的结束时间,而其结束时间对应着种群第2个死亡高峰期的起始时间,表明栲树生长特征是影响其种群年龄结构的关键因素.     

MicroRNA-18 and microRNA-19 regulate CTGF and TSP-1 expression in age-related heart failure

To understand the process of cardiac aging, it is of crucial importance to gain insight into the age‐related changes in gene expression in the senescent failing heart. Age‐related cardiac remodeling is known to be accompanied by changes in extracellular matrix (ECM) gene and protein levels. Small noncoding microRNAs regulate gene expression in cardiac development and disease and have been implicated in the aging process and in the regulation of ECM proteins. However, their role in age‐related cardiac remodeling and heart failure is unknown. In this study, we investigated the aging‐associated microRNA cluster 17–92, which targets the ECM proteins connective tissue growth factor (CTGF) and thrombospondin‐1 (TSP‐1). We employed aged mice with a failure‐resistant (C57Bl6) and failure‐prone (C57Bl6 × 129Sv) genetic background and extrapolated our findings to human age‐associated heart failure. In aging‐associated heart failure, we linked an aging‐induced increase in the ECM proteins CTGF and TSP‐1 to a decreased expression of their targeting microRNAs 18a, 19a, and 19b, all members of the miR‐17–92 cluster. Failure‐resistant mice showed an opposite expression pattern for both the ECM proteins and the microRNAs. We showed that these expression changes are specific for cardiomyocytes and are absent in cardiac fibroblasts. In cardiomyocytes, modulation of miR‐18/19 changes the levels of ECM proteins CTGF and TSP‐1 and collagens type 1 and 3. Together, our data support a role for cardiomyocyte‐derived miR‐18/19 during cardiac aging, in the fine‐tuning of cardiac ECM protein levels. During aging, decreased miR‐18/19 and increased CTGF and TSP‐1 levels identify the failure‐prone heart.     

Genetic diversity patterns in Curcuma reflect differences in genome size

The relationships between genome size and the systematic and evolutionary patterns in vascular plants are equivocal, although a close relationship between genome size and evolutionary patterns has been previously reported. However, several studies have also revealed the dynamic nature of genome size evolution and its considerable ‘ups’ and ‘downs’. Thus, in this study, the phylogenetic relationships among three previously revealed genome size groups and among species of the highly polyploid genus Curcuma were evaluated using AFLP. Our results suggest two main lineages within Indian Curcuma reflecting evolution of genome size. The first one includes hexaploids and higher polyploids of the previously recognized genome size group I, and the second one includes mainly hexaploids of genome size groups II and III. Within genome size group I, relationships among species seem to be influenced by reticulate evolution and higher polyploids are likely to be of allopolyploid origin. Reproductive systems in Indian Curcuma vary considerably among ploidy levels and these differences considerably affect morphological and genetic variation. In general, clonally reproducing species are expected to exhibit low genotypic diversity, but, at the same time, species of allopolyploid origin are expected to maintain higher levels of heterozygosity compared with their progenitors. We investigated intra‐populational genetic variability in Curcuma spp. to evaluate whether mode of reproduction or ploidy represent the main factor influencing the degree of genetic diversity. We found that hexaploid species exhibited significantly higher genetic diversity than higher polyploids (9x, 15x). Our results suggest that this genetic diversity pattern is largely influenced by the mode of reproduction, as higher polyploids reproduce exclusively vegetatively, whereas hexaploids reproduce mainly sexually. © 2011 The Linnean Society of London, Botanical Journal of the Linnean Society, 2011, 165 , 388–401.     

Structure, function, and motility of vacuoles in filamentous fungi

Current information on the structure and function of motile tubular vacuoles in Pisolithus tinctorius and other fungi is reviewed. The use of fluorochromes to label the vacuole lumen is evaluated and observations on the structure and motility of vacuoles in P. tinctorius are differentiated from possible artifacts. The styryl dyes FM4-64 and MDY-64, used in yeast to demonstrate endocytosis, show little or no labeling of internal membranes in undamaged P. tinctorius cells. This agrees with our data showing that other probes for endocytosis such as Lucifer yellow CH are not taken up by hyphal tip cells. Overall, the observations do not support endocytosis in hyphal tips. It has been suggested that tubular vacuole systems carry out longitudinal transport, and evidence in favor of this hypothesis is evaluated. New data are presented to show that many of the large vacuoles in subapical cells are attached to the plasma membrane and are relatively immobile, while video sequences show movement of fluorochrome in pulses along a series of several large vacuoles, all interconnected via tubules. Tubular vacuoles from thick sections of hyphae processed under anhydrous conditions are shown by X-ray microanalysis to contain relatively high levels of P and K, as seen previously in the larger vacuoles. These results provide further evidence for a role of the tubular vacuoles in longitudinal transport of P. Copyright 1998 Academic Press.     

Nitric oxide promotes MPK6‐mediated caspase‐3‐like activation in cadmium‐induced Arabidopsis thaliana programmed cell death

Nitric oxide (NO), a vital cell‐signalling molecule, has been reported to regulate toxic metal responses in plants. This work investigated the effects of NO and the relationship between NO and mitogen‐activated protein kinase (MAPK) in Arabidopsis (Arabidopsis thaliana) programmed cell death (PCD) induced by cadmium (Cd²⁺) exposure. With fluorescence resonance energy transfer (FRET) analysis, caspase‐3‐like protease activation was detected after Cd²⁺ treatment. This was further confirmed with a caspase‐3 substrate assay. Cd²⁺‐induced caspase‐3‐like activity was inhibited in the presence of the NO‐specific scavenger 2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (cPTIO), suggesting that NO mediated caspase‐3‐like protease activation under Cd²⁺ stress conditions. Pretreatment with cPTIO effectively inhibited Cd²⁺‐induced MAPK activation, indicating that NO also affected the MAPK pathway. Interestingly, Cd²⁺‐induced caspase‐3‐like activity was significantly suppressed in the mpk6 mutant, suggesting that MPK6 was required for caspase‐3‐like protease activation. To our knowledge, this is the first demonstration that NO promotes Cd²⁺‐induced Arabidopsis PCD by promoting MPK6‐mediated caspase‐3‐like activation.     

浙江天童国家森林公园常绿阔叶林主要组成种的种群结构及更新类型

 以浙江天童国家森林公园常绿阔叶林为对象,应用永久样方法和每木调查法调查了群落种类组成和结构,并对主要组成种的种群结构进行了分析。依据胸径级频率分布的形状,将各树种的种群结构归纳为5种类型,并结合生物学、生态学特征,分别讨论了其更新类型,同时对调查群落所处的演替阶段进行了诊断。结果表明：1）群落为6种共优势群落,出现木本植物69种。2）种群结构为单峰型的马尾松（Pinus massoniana）、枫香（Liquidambar formosana）和檫木（Sassafras tzumu）等为阳性高大乔木,无正常更新能力,更新类型是先锋群落优势种或是顶极性先锋种;间歇型的木荷（Schima superba）、黑山山矾（Symplocos heishanensis）和红楠（Machilus thunbergii）等为具有耐荫性的常绿阔叶树种,更新具有波动性和机会性,是演替系列或顶极群落优势种;逆-J字型的米槠（Castanopsis carlesii）、栲树（Castanopsis fargesii）和长叶石栎（Lithocarpus harlandii）等为强耐荫性的常绿阔叶树种,通过幼苗库和根萌生枝进行更新,是顶极群落的优势种;浙江新木姜子（Neolitsea aurata var. chekiangensis）、厚皮香（Ternstroemia gymnanthera）等为L字型;连蕊茶（Camellia fraternna）、老鼠矢（Symplocos stellaris）等为单柱型,此二型是群落亚乔木层和灌木层的主要组成种。3）调查群落已进入演替的顶极阶段,但仍处于其前期,将进一步向以米槠、栲树为主要优势种的方向发展。