bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of plant germline development by high‐throughput RNA profiling: technical advances and new insights
Authors: Schmidt Anja , Schmid Marc W. , Grossniklaus Ueli 
Published: March 2012

SummaryReproduction is a crucial step in the life cycle of plants. The male and female germline lineages develop in the reproductive organs of the flower, which in higher plants are the anthers and ovules, respectively. Development of the germline lineage initiates from a dedicated sporophytic cell that undergoes meiosis to form spores that subsequently give rise to the gametophytes through mitotic cell divisions. The mature male and female gametophytes harbour the male (sperm cells) and female gametes (egg and central cell), respectively. Those unite during double fertilization to initiate embryo and endosperm development in sexually reproducing higher plants. While cytological changes involved in development of the germline lineages have been well characterized in a number of species, investigation of the transcriptional basis underlying their development and the specification of the gametes proved challenging. This is largely due to the inaccessibility of the cells constituting the germline lineages, which are enclosed by sporophytic tissues. Only recently, these technical limitations could be overcome by combining new methods to isolate the relevant cells with powerful transcriptional profiling methods, such as microarrays or high‐throughput sequencing of RNA. This review focuses on these technical advances and the new insights gained from them concerning the transcriptional basis and molecular mechanisms underlying germline development.
Glandular trichomes: what comes after expressed sequence tags?
Authors: Tissier Alain 
Published: March 2012

SummaryGlandular trichomes cover the surface of many plant species. They exhibit tremendous diversity, be it in their shape or the compounds they secrete. This diversity is expressed between species but also within species or even individual plants. The industrial uses of some trichome secretions and their potential as a defense barrier, for example against arthropod pests, has spurred research into the biosynthesis pathways that lead to these specialized metabolites. Because complete biosynthesis pathways take place in the secretory cells, the establishment of trichome‐specific expressed sequence tag libraries has greatly accelerated their elucidation. Glandular trichomes also have an important metabolic capacity and may be considered as true cell factories. To fully exploit the potential of glandular trichomes as breeding or engineering objects, several research areas will have to be further investigated, such as development, patterning, metabolic fluxes and transcription regulation. The purpose of this review is to provide an update on the methods and technologies which have been used to investigate glandular trichomes and to propose new avenues of research to deepen our understanding of these specialized structures.
High‐resolution imaging of Ca2+, redox status, ROS and pH using GFP biosensors
Authors: Choi Won‐Gyu , Swanson Sarah J. , Gilroy Simon 
Published: March 2012

SummaryMany plant response systems are linked to complex dynamics in signaling molecules such as Ca2+ and reactive oxygen species (ROS) and to pH. Regulatory changes in these molecules can occur in the timeframe of seconds and are often limited to specific subcellular locales. Thus, to understand how Ca2+, ROS and pH form part of plants’ regulatory networks, it is essential to capture their rapid dynamics with resolutions that span the whole plant to subcellular dimensions. Defining the spatio‐temporal signaling ‘signatures’ of these regulators at high resolution has now been greatly facilitated by the generation of plants expressing a range of GFP‐based bioprobes. For Ca2+ and pH, probes such as the yellow cameleon Ca2+ sensors (principally YC2.1 and 3.6) or the pHluorin and H148D pH sensors provide a robust suite of tools to image changes in these ions. For ROS, the tools are much more limited, with the GFP‐based H2O2 sensor Hyper representing a significant advance for the field. However, with this probe, its marked pH sensitivity provides a key challenge to interpretation without using appropriate controls to test for potentially coupled pH‐dependent changes. Most of these Ca2+‐, ROS‐ and pH‐imaging biosensors are compatible with the standard configurations of confocal microscopes available to many researchers. These probes therefore represent a readily accessible toolkit to monitor cellular signaling. Their use does require appreciation of a minimal set of controls but these are largely related to ensuring that neither the probe itself nor the imaging conditions used perturb the biology of the plant under study.
Surveying the plant’s world by magnetic resonance imaging
Authors: Borisjuk Ljudmilla , Rolletschek Hardy , Neuberger Thomas 
Published: March 2012

SummaryUnderstanding the way in which plants develop, grow and interact with their environment requires tools capable of a high degree of both spatial and temporal resolution. Magnetic resonance imaging (MRI), a technique which is able to visualize internal structures and metabolites, has the great virtue that it is non‐invasive and therefore has the potential to monitor physiological processes occurring in vivo. The major aim of this review is to attract plant biologists to MRI by explaining its advantages and wide range of possible applications for solving outstanding issues in plant science. We discuss the challenges and opportunities of MRI in the study of plant physiology and development, plant–environment interactions, biodiversity, gene functions and metabolism. Overall, it is our view that the potential benefit of harnessing MRI for plant research purposes is hard to overrate.
The structure of the phloem – still more questions than answers
Authors: Knoblauch Michael , Oparka Karl 
Published: March 2012

SummaryLong‐distance assimilate distribution in higher plants takes place in the enucleate sieve‐tube system of the phloem. It is generally accepted that flow of assimilates is driven by an osmotically generated pressure differential, as proposed by Ernst Münch more than 80 years ago. In the period between 1960 and 1980, the pressure flow hypothesis was challenged when electron microscopic images suggested that sieve tubes contain obstructions that would prevent passive flow. This led to the proposal of alternative translocation mechanisms. However, most investigators came to the conclusion that obstructions in the sieve‐tube path were due to preparation artifacts. New developments in bioimaging have vastly enhanced our ability to study the phloem. Unexpectedly, in vivo studies challenge the pressure‐flow hypothesis once again. In this review we summarize current investigations of phloem structure and function and discuss their impact on our understanding of long‐distance transport in the phloem.
Autopolyploidy differentially influences body size in plants, but facilitates enhanced accumulation of secondary metabolites, causing increased cytosine methylation
Authors: Lavania Umesh C. , Srivastava Sarita , Lavania Seshu , Basu Surochita , Misra Nandeesh Kumar , Mukai Yasuhiko 
Published: March 2012

SummaryWhole genome duplication leads to autopolyploidy and brings about an increase in cell size, concentration of secondary metabolites and enhanced cytosine methylation. The increased cell size offers a positive advantage to polyploids for cell‐surface‐related activities, but there is a differential response to change in body size across species and taxonomic groups. Although polyploidy has been very extensively studied, having genetic, ecological and evolutionary implications, there is no report that underscores the significance of native secondary metabolitesvis‐à‐visbody size with ploidy change. To address this problem we targeted unique diploid–autotetraploid paired sets of eight diverse clones of six species ofCymbopogon– a species complex of aromatic grasses that accumulate qualitatively different monoterpene essential oils (secondary metabolite) in their vegetative biomass. Based on the qualitative composition of essential oils and the plant body size relationship between the diploid versus autotetraploid paired sets, we show that polyploidy brings about enhanced accumulation of secondary metabolites in all cases, but exerts differential effects on body size in various species. It is observed that the accumulation of alcohol‐type metabolites (e.g. geraniol) does not inhibit increase in body size with ploidy change from 2× to 4× (r = 0.854,P < 0.01), but aldehyde‐type metabolites (e.g. citral) appear to drastically impede body development (r = −0.895). Such a differential response may be correlated to the metabolic steps involved in the synthesis of essential oil components. When changed to tetraploidy, the progenitor diploids requiring longer metabolic steps in production of their secondary metabolites are stressed, and those having shorter metabolite routes better utilize their resources for growth and vigour.In situimmunodetection of 5‐methylcytosine sites reveals enhanced DNA methylation in autopolyploids. It is underpinned that the qualitative composition of secondary metabolites found in the vegetative biomass of the progenitor diploid has a decisive bearing on the body size of the derived autotetraploids and brings about an enhancement in genome‐wide cytosine methylation.
Unpredictability of nectar nicotine promotes outcrossing by hummingbirds in Nicotiana attenuata
Authors: Kessler Danny , Bhattacharya Samik , Diezel Celia , Rothe Eva , Gase Klaus , Schöttner Matthias , Baldwin Ian T. 
Published: March 2012

SummaryMany plants use sophisticated strategies to maximize their reproductive success via outcrossing. Nicotiana attenuata flowers produce nectar with nicotine at concentrations that are repellent to hummingbirds, increasing the number of flowers visited per plant. In choice tests using native hummingbirds, we show that these important pollinators learn to tolerate high‐nicotine nectar but prefer low‐nicotine nectar, and show no signs of nicotine addiction. Nectar nicotine concentrations, unlike those of other vegetative tissues, are unpredictably variable among flowers, not only among populations, but also within populations, and even among flowers within an inflorescence. To evaluate whether variations in nectar nicotine concentrations increase outcrossing, polymorphic microsatellite markers, optimized to evaluate paternity in native N. attenuata populations, were used to compare outcrossing in plants silenced for expression of a biosynthetic gene for nicotine production (Napmt1/2) and in control empty vector plants, which were antherectomized and transplanted into native populations. When only exposed to hummingbird pollinators, seeds produced by flowers with nicotine in their nectar had a greater number of genetically different sires, compared to seeds from nicotine‐free flowers. As the variation in nectar nicotine levels among flowers in an inflorescence decreased in N. attenuata plants silenced in various combinations of three Dicer‐like (DCL) proteins, small RNAs are probably involved in the unpredictable variation in nectar nicotine levels within a plant.
Chestnut blight in south‐western Germany: multiple introductions of Cryphonectria parasitica and slow hypovirus spread
Authors: Peters F. S. , Holweg C. L. , Rigling D. , Metzler B. 
Published: March 2012

SummaryCryphonectria parasitica was discovered in the sweet chestnut forests of south‐western Germany in 1992. Two main areas affected by chestnut blight were discerned, one to the east and one to the west of the Rhine valley. The occurrence of the fungal pathogen with respect to vegetative compatibility (vc) type and hypovirulence was analysed by sampling chestnut blight cankers between 1992 and 2010. Among 368 C. parasitica isolates sampled in south‐western Germany, 9 different vc types were found. East of the Rhine valley, EU‐2 is the most widespread vc type. In addition, two isolated forest areas infected with C. parasitica of the vc types EU‐14 and EU‐28 were detected. West of the Rhine valley, C. parasitica of the vc type EU‐65 was repeatedly isolated from an infection focus, the spread of which was successfully suppressed for several years by sanitation measures. Since 2003, additional outbreaks of C. parasitica belonging to the vc types EU‐2 and EU‐5 were detected in the vicinity. Several other vc types (EU‐1, EU‐12, EU‐33 and one vc type incompatible with any of the 74 European testers) were identified on isolated trees mainly in urban areas across the study area and were subsequently eradicated. The spatial and temporal distribution of the different vc types indicates at least nine different introductory events of C. parasitica into south‐western Germany. Natural hypovirulence was only found in the infection area in Baden‐Württemberg. A total of four hypovirulent isolates of the vc type EU‐2 were obtained, one in 1992 and three in recent years. The four hypoviruses were genetically closely related and belonged to the Spanish/German subtype of Cryphonectria hypovirus 1. As the different vc types in south‐western Germany occur mostly in spatially separated, single stands, the introduction of hypovirulence as biological control is expected to be effective.
Oxygen Concentration and Cysteamine Supplementation During In vitro Production of Buffalo (Bubalus bubalis) Embryos Affect mRNA Expression of BCL‐2, BCL‐XL, MCL‐1, BAX and BID
Authors: Elamaran G , Singh KP , Singh MK , Singla SK , Chauhan MS , Manik RS , Palta P 
Published: March 2012

ContentsThis study examined the effects of O2 concentration (5% vs 20%) during in vitro maturation (IVM), fertilization (IVF) and culture (IVC) or supplementation of IVM and IVC media with cysteamine (50 and 100 μm, respectively; IVM, IVF and IVC carried out in 20% O2), on blastocyst rate and relative mRNA abundance of some apoptosis‐related genes measured by real‐time qPCR in immature and in vitro‐matured buffalo oocytes and in embryos at 2‐, 4‐, 8‐ to 16‐cell, morula and blastocyst stages. The blastocyst rate was significantly higher (p < 0.05) while the percentage of TUNEL‐positive cells was significantly lower (p < 0.05) under 5% O2 than that under 20% O2. The mRNA expression of anti‐apoptotic genes BCL‐2 and MCL‐1 was significantly higher (p < 0.05) and that of pro‐apoptotic genes BAX and BID was lower (p < 0.05) under 5% O2 than that under 20% O2 concentration at many embryonic stages. Following cysteamine supplementation, the blastocyst rate and the relative mRNA abundance of BCL‐XL and MCL‐1 was significantly higher (p < 0.05) and that of BAX but not BID was lower (p < 0.05) at many stages of embryonic development, although it did not affect the percentage of TUNEL positive cells in the blastocysts significantly. The mRNA expression pattern of these genes during embryonic development was different in 5% vs 20% O2 groups and in cysteamine supplemented vs controls. At the 8‐ to 16‐cell stage, where developmental block occurs in buffalo, the relative mRNA abundance of BCL‐2 and MCL‐1 was highest under 5% O2 concentration and that of BAX and BID was highest (p < 0.05) under 20% O2 concentration. These results suggest that one of the mechanisms through which beneficial effects of low O2 concentration and cysteamine supplementation are mediated during in vitro embryo production is through an increase in the expression of anti‐apoptotic and a decrease in the expression of pro‐apoptotic genes.
Bovine OPU‐Derived Oocytes can be Matured In Vitro for 16–28 h with Similar Developmental Capacity
Authors: Merton JS , de Roos APW , Koenen EPC , Roelen BAJ , Vos PLAM , Mullaart E , Knijn HM 
Published: March 2012

ContentsThe aim of this study was to determine the optimal maturation culture period of ovum pick up (OPU)‐derived cumulus oocytes complexes (COCs) in relation to their developmental capacity. Embryo production, embryo cryotolerance, post‐transfer embryonic survival and calf characteristics such as gestation length, birthweight and sex ratio were investigated. This retrospective study covers the analyses of ovum pick up –in vitro production and calving results from a commercial programme that took place between March 1994 and September 2004. Donors were both heifers (of which approximately 90% pregnant) and cows (of which approximately 10% pregnant). Embryo production analyses were based on 7800 OPU sessions conducted from January 1995 until January 1999. Analyses of calving rate were based on 13 468 embryo transfers performed during January 1995 until May 2002. Analyses on calf characteristics were based on 2162 calves born between March 1994 and September 2004. The in vitro maturation culture period ranged from 16 to 28 h. The mean production rate of transferable embryos was 16.5% (1.2 embryos per OPU session). Length of maturation culture period did not affect the production of transferable embryos. Mean calving rate was 40.9% and 38.7% for fresh and frozen/thawed embryos, respectively. Calving rate was not affected by the maturation culture period. Mean birthweight, gestation length and proportion of male calves were 46 kg, 281.9 days and 52.8%, respectively. Maturation culture period did not affect these variables. In conclusion, this study shows that the in vitro maturation culture period within the range of 16–28 h does not affect in vitro embryo production, embryo cryotolerance, post‐transfer embryonic survival and calf characteristics, suggesting that all COC batches collected by OPU on the same day, can be fertilized in one IVF session without a significant loss in the production from oocyte to calf.
Comparison of Synthetic Oviductal Fluid and G1/G2 Medium under Low‐1 Oxygen Atmosphere on Embryo Production and Pregnancy Rates in Nelore (Bos indicus) Cattle
Authors: Sanches BV , Pontes JHF , Basso AC , Ferreira CR , Perecin F , Seneda MM 
Published: March 2012

ContentsIn this work, we evaluated whether embryo development and pregnancy rates would be affected by culturing bovine Bos indicus embryos in Synthetic Oviductal Fluid with amino acids (SOFaa) or G1/G2 sequential medium under a low‐oxygen atmosphere. Using Ovum Pick Up, we obtained 1,538 oocytes, divided into G1/G2 (n = 783) and SOFaa (n = 755). No difference was observed for blastocyst development among the groups (27.8% ± 14.6 and 34.9% ± 20.0 for G1/G2 and SOFaa respectively, p > 0.05). Transferring the embryos (n = 450) from both groups to recipients resulted in similar pregnancy rates for the G1/G2 (38.4% n = 78/203) compared to the SOFaa (39.7% n = 98/247). Our findings confirm that Bos indicus embryos cultured in SOFaa and G1/G2 under low‐oxygen atmosphere have similar in vitro (blastocyst rate) and in vivo (pregnancy rate) developmental capacity. However, embryos cultured in G1/G2 medium have higher cleavage than those cultured in SOFaa medium.
Health impact and toxicological effects of nanomaterials in the lung
Authors: KENDALL MICHAELA , HOLGATE STEPHEN 
Published: March 2012

ABSTRACTThe manufacture, use and disposal of nanomaterials will result in increased human exposures to engineered nanoparticles (ENPs), potentially via the lung. ENPs differ physically and chemically from natural‐ or combustion‐derived nanoparticles (NP) in important respects. While there are parallels with ultrafine aerosol particles in the atmosphere and colloids in water, there remain some unique issues and impacts of engineered materials on lung health that require consideration and urgent study.The study of toxicity of nanomaterials in biological systems—nanotoxicology—emerged from the observed effects of inhaled particulate matter (PM) and NP. Some engineered nanomaterials deserve special toxicological examination because of their unique properties in biological systems; novel toxicological approaches may be required for their assessment. Translocation in biological systems—a key feature of ENPs—is dependent on ENP size and surface interactions with macromolecules at the portal of entry, upstream of cellular interaction. Of particular significance is the agglomeration processes associated with macromolecule adsorption at ENP surfaces, which determine clearance rates and cellular response. ENP toxicity is therefore dominated by three linked physico‐chemical factors: size‐shape, surface and ‘corona’ (formed by adhering macromolecules from the suscipient host). Measuring and predicting ENP translocation and effects following lung entry have proven to be particularly challenging, but understanding ENP behaviour in vivo is fundamental for safe design for effective and targeted drug delivery. Human exposures via medical and dental applications appear important in terms of dose and toxicity, and may need to be assessed for risk on a case‐by‐case basis.
Patchy distributions of Spirogyra arcta do not affect growth of the submerged macrophyte Ceratophyllum demersum
Authors: LIU RUI‐HUA , DONG BI‐CHENG , LI HONG‐LI , ZHANG QIAN , YU FEI‐HAI 
Published: March 2012

AbstractSpatial heterogeneity is common in aquatic conditions, but few studies have examined the effects of heterogeneous distributions of biological factors on aquatic plants. Spirogyra (Spirogyra arcta) coexists with many submerged macrophytes, such as Ceratophyllum demersum, but no study has examined the effects of heterogeneous distributions of spirogyra on the growth of submerged plants. We grew the submerged plant C. demersum in three homogeneous, aquatic conditions (0, 50 and 100% of the water surface in the container was evenly covered by spirogyra, referred to as ‘control’, ‘50%’ and ‘100%’, respectively) and two patchy conditions (the left half of the water surface in the container was not covered by spirogyra and 50% and 100% of the water surface in the right half of the container was evenly covered by spirogyra, referred to as ‘50%‐patchy’ and ‘100%‐patchy’, respectively). Compared with the control, the 100% treatment greatly decreased the biomass and number of ramets of C. demersum, but the 50% treatment did not. Growth of C. demersum in the left half of the container did not differ significantly between the control and the two heterogeneous treatments (50%‐patchy and 100%‐patchy). In addition, growth of C. demersum in the right half of the container did not differ between the 100% and the 100%‐patchy treatment or between the 50% and the 50%‐patchy treatment. Our results suggest that C. demersum can tolerate shading by spirogyra to a certain extent and that heterogeneous distributions of spirogyra do not affect its growth.