Rangewide analysis of fungal associations in the fully mycoheterotrophic Corallorhiza striata complex (Orchidaceae) reveals extreme specificity on ectomycorrhizal Tomentella (Thelephoraceae) across North America

Fully mycoheterotrophic plants offer a fascinating system for studying phylogenetic associations and dynamics of symbiotic specificity between hosts and parasites. These plants frequently parasitize mutualistic mycorrhizal symbioses between fungi and trees. Corallorhiza striata is a fully mycoheterotrophic, North American orchid distributed from Mexico to Canada, but the full extent of its fungal associations and specificity is unknown. Plastid DNA (orchids) and ITS (fungi) were sequenced for 107 individuals from 42 populations across North America to identify C. striata mycobionts and test hypotheses on fungal host specificity. Four largely allopatric orchid plastid clades were recovered, and all fungal sequences were most similar to ectomycorrhizal Tomentella (Thelephoraceae), nearly all to T. fuscocinerea. Orchid-fungal gene trees were incongruent but nonindependent; orchid clades associated with divergent sets of fungi, with a clade of Californian orchids subspecialized toward a narrow Tomentella fuscocinerea clade. Both geography and orchid clades were important determinants of fungal association, following a geographic mosaic model of specificity on Tomentella fungi. These findings corroborate patterns described in other fully mycoheterotrophic orchids and monotropes, represent one of the most extensive plant-fungal genetic investigations of fully mycoheterotrophic plants, and have conservation implications for the >400 plant species engaging in this trophic strategy worldwide.     

红芽芋球茎片两步法离体快繁及其再生苗生理和光合特性研究

以江西铅山红芽芋(Colocasia esculenta L.Schott var.cormosus‘Hongyayu’)试管苗为材料,建立了芋球茎片两步法离体快繁体系,并对其再生苗的形态指标、染色体数目、生理和光合特性以及叶绿素荧光特性进行了检测。结果表明:(1)红芽芋球茎片单芽诱导的最佳培养基为MS+KT 2 mg/L+6-BA 1 mg/L+NAA0.1mg/L,诱导培养30d后将单芽从球茎片上分离,再接种到生根培养基(MS+KT 2mg/L+NAA 0.1mg/L)上培养30d即可形成完整植株,移栽成活率高达98%;(2)由球茎片单芽、丛生芽、不定芽离体快繁获得的红芽芋再生苗在形态指标、叶下表皮气孔参数、染色体数目、生理生化指标以及叶片光合特性参数和叶绿素荧光特性方面均无显著差异。说明红芽芋球茎片两步法离体培养的再生苗繁殖系数高、染色体数目稳定,该离体快繁体系可应用于江西铅山红芽芋的工厂化生产。     

蔓生百部的化学成分研究

从蔓生百部(Stemona japonica)根中分离得到13个化合物,通过波谱数据,它们鉴定为β-谷甾醇(1)、豆甾醇(2)、5,11-豆甾二烯-3β-醇(3)、苯甲酸(4)、4-甲氧基苯甲酸(5)、1,8-二羟基-3-甲基蒽醌(6)、1,8-二羟基-6-甲氧基-3-甲基蒽醌(7)、氧代狭叶百部碱(8)、百部定碱(9)、异狭叶百部碱(10)、绿原酸(11)、栀子苷(12)和藏红花素A(13).所有化合物均为首次从该植物中分离得到.     

小麦族植物的分类现状及主要存在的问题

小麦族(Triticeae)是禾本科、早熟禾亚科中一个有重要经济价值、以多年生植物占优势的族,族内绝大多数种类是重要的粮食作物和畜牧业上的优良牧草,饲用价值极高,有些种类具有耐寒、耐旱、耐碱等特性,是农牧业上良种繁育、牧草利用的重要基因资源。但该族同时又是分类学上的一个疑难族,各学者对族内系统分类意见不一、争议颇大,尤其在族的界限、族下类群划分以及类群演化关系上问题较多,至今尚未解决。查阅了国内外分类学文献,探讨其分类差异以及存在问题,为充分开发利用中国丰富的小麦族植物资源提供理论依据。     

长江流域植被净第一性生产力及其时空格局研究

 基于生态过程模型——CASA模型,利用1982～1999年18年来8 km×8 km分辨率的遥感数据和匹配的温度、降水、太阳辐射资料以及植被和土壤信息,对长江流域的植被NPP及其时空分布格局进行了分析。主要结论如下：1) 18年来,长江流域年均NPP总量为0.46Pg C·a-1,占全国总量的27.22     

Mating strategies in flowering plants: the outcrossing-selfing paradigm and beyond

Comparisons of the causes and consequences of cross- and self-fertilization have dominated research on plant mating since Darwin's seminal work on plant reproduction. Here, I provide examples of these accomplishments, but also illustrate new approaches that emphasize the role of floral design and display in pollen dispersal and fitness gain through male function. Wide variation in outcrossing rate characterizes animal-pollinated plants. In species with large floral displays, part of the selfing component of mixed mating can arise from geitonogamy and be maladaptive because of strong inbreeding depression and pollen discounting. Floral strategies that separate the benefits of floral display from the mating costs associated with geitonogamy can resolve these conflicts by reducing lost mating opportunities through male function. The results from experiments with marker genes and floral manipulations provide evidence for the function of herkogamy and dichogamy in reducing self-pollination and promoting pollen dispersal. Evidence is also presented indicating that increased selfing resulting from changes to floral design, or geitonogamy in large clones, can act as a stimulus for the evolution of dioecy. The scope of future research on mating strategies needs to be broadened to include investigations of functional links among flowers, inflorescences and plant architecture within the framework of life-history evolution.     

Preserved Proteins from Extinct Bison latifrons Identified by Tandem Mass Spectrometry; Hydroxylysine Glycosides are a Common Feature of Ancient Collagen

Bone samples from several vertebrates were collected from the Ziegler Reservoir fossil site, in Snowmass Village, Colorado, and processed for proteomics analysis. The specimens come from Pleistocene megafauna Bison latifrons, dating back ∼120,000 years. Proteomics analysis using a simplified sample preparation procedure and tandem mass spectrometry (MS/MS) was applied to obtain protein identifications. Several bioinformatics resources were used to obtain peptide identifications based on sequence homology to extant species with annotated genomes. With the exception of soil sample controls, all samples resulted in confident peptide identifications that mapped to type I collagen. In addition, we analyzed a specimen from the extinct B. latifrons that yielded peptide identifications mapping to over 33 bovine proteins. Our analysis resulted in extensive fibrillar collagen sequence coverage, including the identification of posttranslational modifications. Hydroxylysine glucosylgalactosylation, a modification thought to be involved in collagen fiber formation and bone mineralization, was identified for the first time in an ancient protein dataset. Meta-analysis of data from other studies indicates that this modification may be common in well-preserved prehistoric samples. Additional peptide sequences from extracellular matrix (ECM) and non-ECM proteins have also been identified for the first time in ancient tissue samples. These data provide a framework for analyzing ancient protein signatures in well-preserved fossil specimens, while also contributing novel insights into the molecular basis of organic matter preservation. As such, this analysis has unearthed common posttranslational modifications of collagen that may assist in its preservation over time. The data are available via ProteomeXchange with identifier PXD001827.During the last decade, paleontology and taphonomy (the study of decaying organisms over time and the fossilization processes) have begun to overlap with the field of proteomics to shed new light on preserved organic matter in fossilized bones (1–4). These bones represent a time capsule of ancient biomolecules, owing to their natural resistance to post mortem decay arising from a unique combination of mechanical, structural, and chemical properties (4–7).Although bones can be cursorily described as a composite of collagen (protein) and hydroxyapatite (mineral), fossilized bones undergo three distinct diagenesis pathways: (i) chemical deterioration of the organic phase; (ii) chemical deterioration of the mineral phase; and (iii) (micro)biological attack of the composite (6). In addition, the rate of these degradation pathways are affected by temperature, as higher burial temperatures have been shown to accelerate these processes (6, 8). Though relatively unusual, the first of these three pathways results in a slower deterioration process, which is more generally mitigated under (6) specific environmental constraints, such as geochemical stability (stable temperature and acidity) that promote bone mineral preservation. Importantly, slower deterioration results in more preserved biological materials that are more amenable to downstream analytical assays. One example of this is the controversial case of bone and soft-tissue preservation from the Cretaceous/Tertiary boundary (9–22). In light of these and other studies of ancient biomolecules, paleontological models have proposed that organic biomolecules in ancient samples, such as collagen sequences from the 80 million-year-(my)-old Campanian hadrosaur, Brachylophosaurus canadensis (16) or 68-my-old Tyrannosaurus rex, might be protected by the microenvironment within bones. Such spaces are believed to form a protective shelter that is able to reduce the effects of diagenetic events. In addition to collagen, preserved biomolecules include blood proteins, cellular lipids, and DNA (4, 5). While the maximum estimated lifespan of DNA in bones is ∼20,000 years (ky) at 10 °C, bone proteins have an even longer lifespan, making them an exceptional target for analysis to gain relevant insights into fossilized samples (6). Indeed, the survival of collagen, which is considered to be the most abundant bone protein, is estimated to be in the range 340 ky at 20 °C. Similarly, osteocalcin, the second-most abundant bone protein, can persist for ≈45 ky at 20 °C, thus opening an unprecedented analytical window to study extremely old samples (2, 4, 23).Although ancient DNA amplification and sequencing can yield interesting clues and potential artifacts from contaminating agents (7, 24–28), the improved preservation of ancient proteins provides access to a reservoir of otherwise unavailable genetic information for phylogenetic inference (25, 29, 30). In particular, mass spectrometry (MS)-based screening of species-specific collagen peptides has recently been used as a low-cost, rapid alternative to DNA sequencing for taxonomic attribution of morphologically unidentifiable small bone fragments and teeth stemming from diverse archeological contexts (25, 31–33).For over five decades, researchers have presented biochemical evidence for the existence of preserved protein material from ancient bone samples (34–36). One of the first direct measurements was by amino acid analysis, which showed that the compositional profile of ancient samples was consistent with collagens in modern bone samples (37–39). Preservation of organic biomolecules, either from bone, dentin, antlers, or ivory, has been investigated by radiolabeled ¹⁴C fossil dating (40) to provide an avenue of delineating evolutionary divergence from extant species (3, 41, 42). It is also important to note that these parameters primarily depend on ancient bone collagen as the levels remain largely unchanged (a high percentage of collagen is retained, as gleaned by laboratory experiments on bone taphonomy (6)). Additionally, antibody-based immunostaining methods have given indirect evidence of intact peptide amide bonds (43–45) to aid some of the first evidence of protein other than collagen and osteocalcin in ancient mammoth (43) and human specimens (46).In the past, mass spectrometry has been used to obtain MS signals consistent with modern osteocalcin samples (2, 47), and eventually postsource decay peptide fragmentation was used to confirm the identification of osteocalcin in fossil hominids dating back ∼75 ky (48). More recently, modern “bottom-up” proteomic methods were applied to mastodon and T. rex samples (10), complementing immunohistochemistry evidence (13, 17). The results hinted at the potential of identifying peptides from proteolytic digest of well-preserved bone samples. This work also highlighted the importance of minimizing sources of protein contamination and adhering to data publication guidelines (20, 21). In the past few years, a very well-preserved juvenile mammoth referred to as Lyuba was discovered in the Siberian permafrost and analyzed using high-resolution tandem mass spectrometry (29). This study was followed with a report by Wadsworth and Buckley (30) describing the analysis of proteins from 19 bovine bone samples spanning 4 ky to 1.5 my. Both of these groups reported the identification of additional collagen and noncollagen proteins.Recently, a series of large extinct mammal bones were unearthed at a reservoir near Snowmass Village, Colorado, USA (49, 50). The finding was made during a construction project at the Ziegler Reservoir, a fossil site that was originally a lake formed at an elevation of ∼2,705 m during the Bull Lake glaciations ∼140 ky ago (49, 51). The original lake area was ∼5 hectares in size with a total catchment of ∼14 hectares and lacked a direct water flow inlet or outlet. This closed drainage basin established a relatively unique environment that resulted in the exceptional preservation of plant material, insects (52), and vertebrate bones (49). In particular, a cranial specimen from extinct Bison latifrons was unearthed from the Biostratigraphic Zone/Marine Oxygen Isotope Stage (MIS) 5d, which dates back to ∼120 ky (53, 54).Here, we describe the use of paleoproteomics, for the identification of protein remnants with a focus on a particularly unique B. latifrons cranial specimen found at the Ziegler site. We developed a simplified sample processing approach that allows for analysis of low milligram quantities of ancient samples for peptide identification. Our method avoids the extensive demineralization steps of traditional protocols and utilizes an acid labile detergent to allow for efficient extraction and digestion without the need for additional sample cleanup steps. This approach was applied to a specimen from B. latifrons that displayed visual and mechanical properties consistent with the meninges, a fibrous tissue that lines the cranial cavity. Bioinformatics analysis revealed the presence of a recurring glycosylation signature in well-preserved collagens. In particular, the presence of glycosylated hydroxylysine residues was identified as a unique feature of bone fossil collagen, as gleaned through meta-analyses of raw data from previous reports on woolly mammoth (Mammuthus primigenius) and bovine samples (29, 30). The results from these meta-analyses indicate a common, unique feature of collagen that coincides with, and possibly contributes to its preservation.     

Motoneuron dendrites: role in synaptic integration.

Dendrites constitute over 80 per cent of the receptive surface area in cat motoneurons. Calculations based on matched electrical and gemoetrical measurements in these neurons indicate that the specific resistance of dendritic membranes in resting motoneurons is at least 2,000 ohm-cm2. When the specific membrane resistance is this high, even the most distal dendritic synapses can contribute significantly to the depolarization of the soma, and hence influence the rate of action potential generation. However, dendritic membrane resistance depends strongly on the level of background synaptic activity. The conductance changes associated with excitatory synaptic activity on a dendrite can be great enough to reduce significantly both the excitatory synaptic driving potential and the effective membrane resistance on that dendrite, and thus greatly reduce the effectiveness of synapses on the dendrite. Inhibitory synaptic activity produces an even greater reduction in dendritic membrane resistance. Thus the relative effectiveness of dendritic synapses depends on the type, distribution, and intensity of background synaptic activity, as well as on dendritic geometry and resting membrane properties.     

Importance of Hydrologic and Landscape Heterogeneity for Restoring Bank Swallow (Riparia riparia) Colonies along the Sacramento River, California

Human activities have degraded riparian systems in numerous ways, including homogenization of the floodplain landscape and minimization of extreme flows. We analyzed the effects of changes in these and other factors for extinction–colonization dynamics of a threatened Bank Swallow population along the upper Sacramento River, California, U.S.A. We monitored Bank Swallow distributions along a 160‐km stretch of the river from 1986–1992 and 1996–2003 and tested whether site extinctions and colonizations corresponded with changes in maximum river discharge, surrounding land cover, estimated colony size, temperature, and precipitation. Colonization probabilities increased with maximum discharge. Extinction probabilities decreased with proximity to the nearest grassland, decreased with colony size, and increased with maximum discharge. To explore the implications for restoration, we incorporated the statistically estimated effects of distance to grassland and maximum discharge into simple metapopulation models. Under current conditions, the Bank Swallow metapopulation appears to be in continued decline, although stable or increasing numbers cannot be ruled out with the existing data. Maximum likelihood parameters from these regression models suggest that the Sacramento River metapopulation could be restored to 45 colonies through moderate amounts of grassland restoration, large increases in discharge, or direct restoration of nesting habitat by removing approximately 10% of existing bank protection (riprap) from suitable areas. Our results highlight the importance of grassland restoration, mixed benefits of restoring high spring discharge, and the importance of within‐colony dynamics as areas for future research.